The Potential Role of Human Derived Amniotic Membrane Graft in The Repair of Induced Tendon Tear in Adult Male Albino Rat: Histological Study

QJM ◽  
2021 ◽  
Vol 114 (Supplement_1) ◽  
Author(s):  
Dalia Ahmed Yousef Yehia ◽  
Somaya Abd Al Aleem Mohammed ◽  
Gehan Khalaf Megahed ◽  
Nevine Bahaa El din Mohamed Soliman
Keyword(s):  
Achilles Tendon ◽  
Adult Male ◽  
Amniotic Membrane ◽  
Treated Group ◽  
Human Amniotic Membrane ◽  
Tendon Tear ◽  
Group Iii ◽  
Tendon Tears ◽  
Group Ii

Abstract Introduction Achilles tendon tears cause severe impairment in patient mobility and productivity, causing significant reduction in the quality of life. Many complications are associated with the tendon healing process such as peritendinous adhesions and excessive fibrotic scars. Unsatisfactory results appeared with the existing medical and surgical treatments to regain full tendon structure and function. Amniotic membrane is avascular, and characterized by low immunogenicity, anti-inflammatory, antiscarring properties. These criteria render it as a natural biological substitute and a novel therapeutic alternative for tendon tears. Aim: The aim of the work was to study the effect of human amniotic membrane graft application on the repair of induced Achilles tendon tear. Material and methods Fresh human amniotic membrane (AM) grafts were prepared from harvested human full-term caesarian sections-delivered placentas. Thirty adult male albino rats were divided into 3 equal groups (n = 10); group I (control group), group II (tendon tear group) and group III (AM treated group). After anesthesia, a full thickness transverse incision was induced in the rat right Achilles tendons of group II and III. Human derived amniotic membrane graft measuring 1 cm2 was applied circumferentially on the tendon tear in group III. Rats were sacrificed after 28 days. Results After the tendon tear, the untreated group (II) showed gradual accumulation of fat cells replacing the collagen bundles in focal areas. Areas of mononuclear cellular infiltration were demonstrated. The AM-treated group showed many thick parallel regularly arranged collagen fibers with a significant increase in the collagen fibers area percentage. It also showed apparent increase in tenoblasts with regular organization and apparent decrease of mononuclear inflammatory cells. Conclusion This study demonstrated the potential therapeutic role of the application of human amniotic membrane grafts in the repair of Achilles tendon tears, suggesting a future alternative therapy for patients suffering from Achilles tendon tears.

Role of leukocyte CD11/CD18 complex in endotoxic and septic shock in rabbits

1992 ◽  
Vol 73 (4) ◽  
pp. 1510-1516 ◽  
Author(s):  
J. R. Thomas ◽  
J. M. Harlan ◽  
C. L. Rice ◽  
R. K. Winn
Keyword(s):  
Monoclonal Antibody ◽  
Treated Group ◽  
Saline Group ◽  
Ringer Solution ◽  
Group Iii ◽  
Lung Permeability ◽  
Group I ◽  
Group Ii

Two models of sepsis were investigated using rabbits. In the first model, rabbits given lipopolysaccharide (LPS) were treated with saline (group II) or CD18 monoclonal antibody (MAb) 60.3 (group III). Group I animals received no LPS. Cardiac output was maintained by infusion of lactated Ringer solution with group II (95 +/- 68 ml/kg) requiring significantly more than group I (0 +/- 0 ml/kg) or group III (39 +/- 27 ml/kg). Lung permeability indexes in groups II (median 0.002, range 0.023) and III (median 0.0035, range 0.053) were not different but were significantly greater than group I (median 0.0007, range 0.001). In the second model, peritonitis was produced by devascularizing the appendix, leaving it in situ for 19 h, and then performing an appendectomy. Saline or MAb 60.3 treatment was at appendectomy and every 12 h for 3 days. Survival was significantly greater in the MAb 60.3-treated group at day 10 (90 vs. 40%). Lung permeability was increased at day 2 and was not different between groups. Day 1 fluid requirements were greater in the saline-treated group. These data are consistent with MAb 60.3 protection of systemic but not pulmonary circulation in two models of sepsis.

A Histological Study on the Effect of Dextrose Prolotherapy on Skeletal Muscle Injury in Adult Male Albino Rats

QJM ◽  
2021 ◽  
Vol 114 (Supplement_1) ◽  
Author(s):  
Eman diaa eldeen ◽  
Azza Salah El Din Soliman ◽  
Rania Ahmed Salah El Din ◽  
George Fayek Barsoum Hanna ◽  
Shereen Adel Saad
Keyword(s):  
Skeletal Muscle ◽  
Adult Male ◽  
Muscle Injury ◽  
Treated Group ◽  
Untreated Group ◽  
Control Group ◽  
Albino Rats ◽  
Muscle Injuries ◽  
Group Iii ◽  
Group Ii

Abstract Background Skeletal muscle injuries are one of the most common injuries occurring in sport medicine varies from 10% to 55% of all injuries. Phases of muscle injuries includes a series of complex stages including inflammation, regeneration and remodeling. Treatment of the injuries is based on conservative measures as rest, elevation, physical therapy and non steroidal anti-inflammatory medications. Many injection protocols have been proposed for the treatment of muscle lesions as corticosteroid injection. Recently prolotherapy appears to have a safety profile comparable with other injection procedures. Aim of the work The aim of the present work is to determine the efficacy of dextrose prolotherapy in treatment of skeletal muscle injury in adult male albino rats. Material and methods Sixty six adult male albino rats were used in the study. They were divided into control (group I) and experimental groups. Control group: rats were left without any intervention. The experimental group was group II that was divided into sham operated group in which skin incision was done in the left hindlimb without injury to gastrocnemius (group II`) and muscle injury group in which transverse cut injury across the midbelly of the gastrocnemius muscle of right hindlimb was done (group II``) and group III that was divided into lidocaine injected group in which skin incision in lefthindlimb was done without injury to gastrocnemius followed by injection of 0.3 ml 1% lidocaine was injected across the muscle (group III`) and muscle injury treated with dextrose prolotherapy group in which a transverse cut injury across the midbelly of gastrocnemius of right hindlimb was done followed by injection of 0.1 ml of dextrose prolotherapy of mixture of 0.1ml of 12.5% dextrose and 0.3 ml of 1% lidocaine (group III``). The animals were received 6 injections of lidocaine and dextrose prolotherapy at 5 days interval (starting from day 0 to day 25). In group II and III, muscle specimens were taken at 5,12 and 28 days and processed for light microscope Results Examination of Group II``A (5 days untreated group) showed intense infiltration of mononucleated inflammatory cells intermingling with dispersed myoblasts and macrophages. Group II`` B (12 days untreated group) showed regenerating myotubes intermingling with mononuclear inflammatory infiltrate and macrophages. Group II``C (28 days untreated group) showed some muscle fibers with peripherally elongated nuclei while others showed centrally vesicular ones. Examination of group III``A (5 day treated group with prolotherapy) showed longitudinal regenerating myofibers with multiple rows of internal vesiculated nuclei. Group III``B (12 days treated group) showed newly formed myofibers with incomplete striations together with well developed newly formed striated longitudinal muscle bundles with peripheral flattened nuclei, group III``C (28 days treated group) showed cross striated muscle fibers with the appearance of elongated vesicular nuclei. Conclusions dextrose prolotherapy was effective in soft tissue healing as it accelerated myoblast proliferation and differentiation

Genoprotective role of vitamin E and selenium in rabbits anaesthetized with sevoflurane

2004 ◽  
Vol 23 (8) ◽  
pp. 413-419 ◽  
Author(s):  
Cetin Kaymak ◽  
Ela Kadioglu ◽  
Hulya Basar ◽  
Semra Sardas
Keyword(s):  
Dna Damage ◽  
Vitamin E ◽  
Comet Assay ◽  
Antioxidant Supplementation ◽  
Group Iii ◽  
Sevoflurane Anaesthesia ◽  
Group I ◽  
The Mean ◽  
Group Ii

In this study, genotoxic effects of repeated sevoflurane anaesthesia were investigated in rabbits with or without antioxidant supplementation. Twenty-one New Zealand male rabbits were included in the study and randomized into three groups as: placebo treated (Group I), vitamin E supplemented (Group II) and selenium supplemented (Group III). Vitamin E and selenium were given intraperitoneally for 15 days before anaesthesia treatment. Anaesthesia was administered using 3% sevoflurane in 4 L/min oxygen for a 3-hour period and continued for 3 days. Blood samples were collected before anaesthesia (Sample 1), after the first, second and third days of sevoflurane administration (Sample 2, Sample 3 and Sample 4 respectively) and the last samples were taken 5 days after the last sevoflurane administration (Sample 5). Genotoxic damage was examined using the comet assay. The degree of damage is assessed by grading the cells into three categories of no migration (NM), low migration (LM) and high migration (HM) depending on the fraction of DNA pulled out into the tail under the influence of the electric field. The number of comets in each sample was calculated (1 × number of comets in category NM + 2 × number of comets in category LM + 3 ×number of comets in category HM) and expressed as the total comet score (TCS), which summarizes the damage frequencies. In Group I, a significant increase in the mean TCSs was observed for Samples 3 and 4 as compared with Sample 1. However, there were no significant differences between Samples 1, 2 and 5. The mean TCS of Sample 4 was significantly higher than Sample 1, 2 and 3 in Group II. Group III demonstrated no significant mean TCSs for any experimental conditions. Statistical differences were also observed between the groups with significant P values. This experimental study points out the presence of DNA damage with repeated sevoflurane anaesthesia and the genoprotective role of antioxidant supplementation on DNA damage in mononuclear leukocytes of rabbits by highly sensitive comet assay.

Endothelin effects in isolated, perfused lamb lungs: role of cyclooxygenase inhibition and vasomotor tone

1991 ◽  
Vol 261 (2) ◽  
pp. H443-H450 ◽  
Author(s):  
H. Toga ◽  
J. Usha Raj ◽  
R. Hillyard ◽  
B. Ku ◽  
J. Anderson
Keyword(s):  
Vasomotor Tone ◽  
Cyclooxygenase Inhibition ◽  
Group Iii ◽  
Group I ◽  
Before And After ◽  
Pulmonary Arterial ◽  
Group Ii ◽  
Sites Of Action ◽  
Arteries And Veins

We have determined the sites of action of endothelin-1 (ET) in the lamb pulmonary circulation. The influence of cyclooxygenase inhibition and baseline vasomotor tone on ET effects was also studied. Lungs of 14 lambs (6-9 wk of age, 12.1 +/- 0.6 kg body wt) were isolated and perfused with blood. Group I lungs (n = 5) were untreated, group II lungs (n = 5) were treated with indomethacin to inhibit cyclooxygenase, and group III lungs (n = 4) were treated with indomethacin and a thromboxane A2 analogue, U-46619, to elevate vasomotor tone. All lungs were perfused with constant flow in zone 3, with left atrial and airway pressures being 8 and 6 cmH2O, respectively. We measured pulmonary arterial pressure and, by the micropuncture servo-null method, pressures in 20- to 50-microns diameter subpleural venules, both before and after each dose of ET was infused (50, 100, 250, and 500 ng/kg). Group I lungs, with high baseline vasomotor tone, exhibited a biphasic response to ET; 50-100 ng/kg of ET dilated both arteries and veins, whereas 500 ng/kg of ET constricted both arteries and veins. In group II lungs with low vasomotor tone, all doses of ET caused constriction of arteries only. In group III lungs (indomethacin treated with elevated vasomotor tone), 50-100 ng/kg of ET caused dilation of arteries and veins, whereas 500 ng/kg of ET induced constriction, this time only in arteries. We conclude that ET has both dilator and constrictor effects in arteries and veins of isolated, perfused lamb lungs. ET-induced arterial and venous dilation is dependent on initial vasomotor tone but not on cyclooxygenase metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The prognostic role of inflammatory markers in COVID 19 patients – A retrospective analysis.

2021 ◽  
Author(s):  
Shivkumar Gopalakrishnan ◽  
sangeetha kandasamy ◽  
S.Malini ◽  
S.Peer Mohamed ◽  
k.velmurugan
Keyword(s):  
Inflammatory Markers ◽  
Severe Disease ◽  
Radiation Hazard ◽  
P Value ◽  
Binary Logistic Regression Analysis ◽  
Group Iii ◽  
Group I ◽  
Group Ii ◽  
D Dimer

Abstract Background. Approximately 5% of COVID-19 patients suffer near fatal disease. Clinical and radiologic features may predict severe disease albeit with limited specificity and radiation hazard. Laboratory biomarkers are eyed as simple, specific and point of care triage tools to optimize management decisions.This study aimed to study the role of inflammatory markers in prognosticating COVID-19 patients.Methodology. A hospital based retrospective study was conducted on COVID-19 adult inpatients classified into three groups as mild disease-recovered [Group I], severe disease-recovered [Group II] and dead [Group III]. Categorical outcomes were compared using Chi square test. Univariate binary logistic regression analysis was performed to test the association between the explanatory and outcome variables. Unadjusted OR along with 95% CI was calculated. The utility of lab parameters (Ferritin, LDH, D dimer, N/L ratio and PLT/L ratio) in predicting severity of COVID-19 was assessed by Receiver Operative Curve (ROC) analysis. P value < 0.05 was considered statistically significant.Results. The mean age was 49.32 +/- 17.1 years. Among study population, 378 were Group I, 66 Group II, and 56 Group III. Median levels of Ferritin among the 3 groups were 62ng/mL, 388.50 ng/mL and 1199.50 ng/mL. Median value of LDH were 95U/L, 720 and 982.50(p <0.001). D-dimer values of 3 groups were 23.20ng/mL, 104.30 ng/mL and 197.10 ng/mL (p <0.001). CRP done qualitatively was positive in 2 (0.53%), 30 (45.45%) and 53 (94.64%) of patients. The odds of patients suffering severe COVID-19 rose with rising values of ferritin, LDH and D-dimer [unadjusted OR 1.007, 1.004 &1.020]Conclusion. One time measurement of serum ferritin, LDH, D-dimer and CRP is promising to predict outcomes for COVID 19 inpatients. Single qualitative CRP was equally good but more cost effective than quantitative CRP. The most specific combination was NLR, Lymphocyte percentage and D-dimer levels done between 7th – 10th day of symptoms.

scholarly journals The Effect of Induced Diabetes Mellitus on the Cerebellar Cortex of Adult Male Rat and the Possible Protective Role of Oxymatrine: A Histological, Immunohistochemical and Biochemical Study

2021 ◽  
Author(s):  
Amany Mohamed Shalaby ◽  
Adel Mohamed Aboregela ◽  
Mohamed Ali Alabiad ◽  
Mona Tayssir Sadek
Keyword(s):  
Diabetes Mellitus ◽  
Purkinje Cells ◽  
Cerebellar Cortex ◽  
Adult Male ◽  
Protective Role ◽  
Diabetic Rats ◽  
Male Rats ◽  
Group I ◽  
Group Ii

Abstract Diabetes mellitus (DM) represents a widespread metabolic disease with a well-known neurotoxicity in both central and peripheral nervous systems. Oxymatrine is a traditional Chinese herbal medicine that has various pharmacological activities including; anti-oxidant, anti-apoptotic and anti-inflammatory potentials. The present work aimed to study the impact of diabetes mellitus on the cerebellar cortex of adult male albino rat and to evaluate the potential protective role of oxymatrine using different histological methods. Fifty-five adult male rats were randomly divided into three groups: group I served as control, group II was given oxymatrine (80 mg/kg/day) orally for 8 weeks and group III was given a single dose of streptozotocin (50mg/kg) intaperitoneally to induce diabetes. Then diabetic rats were subdivided into two subgroups: subgroup IIIa that received no additional treatment and subgroup IIIb that received oxymatrine similar to group II. The diabetic group revealed numerous changes in the Purkinje cell layer in the form of multilayer arrangement of Purkinje cells, shrunken cells with deeply stained nuclei as well as focal loss of the Purkinje cells. A significant increment in GFAP and synaptophysin expression was reported. Transmission electron microscopy showed irregularity and splitting of myelin sheaths in the molecular layer, dark shrunken Purkinje cells with ill-defined nuclei, dilated Golgi saccules and dense granule cells with irregular nuclear outlines in the granular layer. In contrast, these changes were less evident in diabetic rats that received oxymatrine. In conclusion, Oxymatrine could protect the cerebellar cortex against changes induced by DM.

Neuroprotective role of Curcuma amada in F1 progeny of Juvenile Danio rerio (Zebrafish) from Nickel Chloride Induced Maternal Stress in Gestationally Challenged Adult Fishes

2021 ◽  
pp. 4215-4220
Author(s):  
Sudha N ◽  
Arambakkam Janardhanam Vanisree
Keyword(s):  
Danio Rerio ◽  
Ethyl Acetate Extract ◽  
Juvenile Fish ◽  
Nickel Chloride ◽  
Exposed Group ◽  
Group Iii ◽  
Curcuma Amada ◽  
F1 Progeny ◽  
Group Ii

Background: Nickel chloride, a widely occurring heavy metal compound is reported to be neuro toxic to organisms. It was shown to cause detrimental behaviour and biochemical changes. However, its effect on the nervous system of offspring of the victimized organisms and the combating strategies remain unexplained. Such studies could broaden our knowledge on the detrimental effect of toxic compounds and help in developing suitable combating strategies. Purpose: To evaluate the neuroprotective role of ethyl acetate extract (EA) of Curcuma amada in the brain of F1 progeny of Danio rerio (Zebrafish) which has been gestationally exposed to neurotoxicant nickel chloride. Methods: The group distribution of the study was Group I-Control Juvenile Fish, Group II-Juvenile fish obtained from female fishes subjected to nickel chloride exposure for 50 days, Group III-Juvenile fish obtained from female fish subjected to nickel chloride exposure and co- treated with EA extract of Curcuma amada (150µg) from 30th day to 50th day, Group-IV-Juvenile fish treated with EA extract of Curcuma amada (150µg) for 50 days. Neuroprotective role of ethyl acetate extract of Curcuma amada was evaluated in the juvenile fish (F1 progeny) by performing anxiety and memory test, visualizing ultra-structural changes of juvenile brain using transmission electron microscopy and biochemical assay of membrane bound enzymes. Result: In Colour preference test, there was marked reduction in anxiety behavior in the F1 progeny of exposed fish co treated with EA extract of Curcuma amada (Group III) compared to F1 progeny of metal exposed group (Group-II). In the novel object rejection test, there was a marked improvement in the memory and learning pattern of the EA extract of Curcuma amada treated fishes (Group III) compared to F1 progeny of metal exposed group (Group-II). TEM analysis showed clumped and condensed chromatin, peripheral margination and empty mitochondria with loss of cristae and lipid droplets in Nickel exposed model (Group-II) which was found to be alleviated in EA extract of Curcuma amada co-treated group (Group-III). Altered activities of Calcium ATPases and Sodium potassium ATPases was noted in Nickel chloride exposed Group (Group-II) which however were regulated by EA extract of Curcuma amada. Conclusion: The study suggests that Curcuma amada could combat the toxic effect of nickel chloride in the juvenile fish, the progeny of the exposed adult female.

scholarly journals Effects of doxorubicin associated with amniotic membrane stem cells in the treatment of canine inflammatory breast carcinoma (IPC-366) cells

2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Jéssica Borghesi ◽  
Sara Caceres ◽  
Lara Carolina Mario ◽  
Angela Alonso-Diez ◽  
Ana Carolina Silveira Rabelo ◽  
...  
Keyword(s):  
Stem Cells ◽  
Flow Cytometry ◽  
Amniotic Membrane ◽  
Triple Negative ◽  
Cellular Growth ◽  
Control Group ◽  
Group Iii ◽  
Chemotherapy Drugs ◽  
Group I ◽  
Group Ii

Abstract Background Tumours in mammary glands represent the most common neoplasia in bitches, as in humans. This high incidence results in part from the stimulation of sex hormones on these glands. Among mammary tumours, inflammatory carcinoma is the most aggressive, presenting a poor prognosis to surgical treatment and chemotherapy. One of the most widely used chemotherapy drugs for breast cancer treatment is doxorubicin (DOXO). Alternative therapies have been introduced in order to assist in these treatments; studies on treatments using stem cells have emerged, since they have anti-inflammatory and immunomodulatory properties. The aim of this study was to evaluate the effects of DOXO and canine amniotic membrane stem cells (AMCs) on the triple-negative canine inflammatory mammary carcinoma cell line IPC-366. Methods Four experimental groups were analysed: a control group without treatment; Group I with DOXO, Group II with AMC and Group III with an association of DOXO and AMCs. We performed the MTT assay with DOXO in order to select the best concentration for the experiments. The growth curve was performed with all groups (I-III) in order to verify the potential of treatments to reduce the growth of IPC-366. For the cell cycle, all groups (I-III) were tested using propidium iodide. While in the flow cytometry, antibodies to progesterone receptor (PR), estrogen receptor (ER), PCNA, VEGF, IL-10 and TGF-β1 were used. For steroidogenic pathway hormones, an ELISA assay was performed. Results The results showed that cells treated with 10 µg/mL DOXO showed a 71.64% reduction in cellular growth after 72 h of treatment. Reductions in the expression of VEGF and PCNA-3 were observed by flow cytometry in all treatments when compared to the control. The intracellular levels of ERs were also significantly increased in Group III (4.67% vs. 27.1%). Regarding to the levels of steroid hormones, significant increases in the levels of estradiol (E2) and estrone sulphate (S04E1) were observed in Groups I and III. On the other hand, Group II did not show differences in steroid hormone levels in relation to the control. We conclude that the association of DOXO with AMCs (Group III) promoted a reduction in cell growth and in the expression of proteins related to proliferation and angiogenesis in IPC-366 triple-negative cells. Conclusions This treatment promoted ER positive expression, suggesting that the accumulated oestrogen conducted these cells to a synergistic state, rendering these tumour cells responsive to ERs and susceptible to new hormonal cancer therapies.

Management of Pancreatic Fluid Collections: A Changing of the Guard from Surgery to Endoscopy

2011 ◽  
Vol 77 (12) ◽  
pp. 1650-1655 ◽  
Author(s):  
Shyam Varadarajulu ◽  
C. Mel Wilcox ◽  
Sahibzada Latif ◽  
Milind Phadnis ◽  
John D. Christein
Keyword(s):  
Practice Patterns ◽  
Treated Group ◽  
Pancreatic Fluid Collections ◽  
Pancreatic Fluid ◽  
Group I ◽  
Impacting Factors ◽  
Transmural Drainage ◽  
Group Ii ◽  
Fluid Collections

The aim of this study was to assess for any trend in management of pancreatic fluid collections (PFCs) and identify impacting factors. The endoscopy and surgical databases were queried for PFC patients. PFCs were categorized as pseudocysts (PP) or complex collections (CC) that included abscess/necrosis. The outcome measures were to compare the utilization of surgery and endoscopy from 2004 to 2007 (group I) and from 2008 to 2010 (group II) and identify factors impacting practice patterns. A total of 285 patients were treated: group I included 119 and group II 166. Of 119 group I patients, 29 per cent were treated by surgery and 71 per cent by endoscopy. Of 85 endoscopy patients, 42 per cent were drained by conventional transmural drainage and 58 per cent by endoscopic ultrasound (EUS). Of 166 group II patients, 31 per cent were treated surgically and 69 per cent endoscopically. Of the 115 endoscopy patients, 17 per cent were drained by conventional transmural drainage and 83 per cent by EUS. Compared with group I, all pseudocysts in group II were treated by endoscopy (84% vs 100%, P = 0.001). There was no difference in the rate of CC treated by endoscopy between both groups (57.7% vs 56.8%, P = 0.9). PFCs not causing luminal compression ( P < 0.0001) or measuring <9 cm in size ( P < 0.0001) were more likely to require EUS. There was a significant trend at our institution in the management of PFCs with all pseudocysts presently being treated only by endoscopy. The ability of EUS to access smaller size PFCs and those not causing luminal compression has significantly expanded the role of endoscopy in PFC management.

Exposure of energy-depleted rat trabeculae to low pH improves contractile recovery: role of calcium

1995 ◽  
Vol 268 (4) ◽  
pp. H1510-H1520 ◽  
Author(s):  
C. van Hardeveld ◽  
V. J. Schouten ◽  
A. Muller ◽  
E. T. van der Meulen ◽  
G. Elzinga
Keyword(s):  
Recovery Period ◽  
Muscle Tension ◽  
Low Ph ◽  
Tyrode Solution ◽  
Normal Medium ◽  
Group Iii ◽  
Group I ◽  
Group Ii ◽  
Saving Effect

The beneficial effect of low pH during cardiac ischemia on reperfusion injury has often been attributed to its energy-saving effect due to inhibition of contraction. The role of low pH on Ca2+ accumulation and muscle tension was assessed in energy-depleted tissue by changing the pH of the medium from 7.4 to 6.2 at onset of rigor development during metabolic inhibition (MI), i.e., in the energy-depleted phase. Cytosolic free Ca2+ ([Ca2+]i) and intracellular H+ (pHi) were measured in rat trabeculae at 20 degrees C with fura 2 and 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, respectively, and tension was recorded. The preparations were energy depleted by stimulation at 1 Hz in glucose-free Tyrode solution with 2 mM NaCN. Rigor developed within 20 min, indicating energy depletion. Resting [Ca2+]i was followed during 50 min (group I) or 100 min (group II) of rigor, and recovery was followed for 60 min in glucose-containing Tyrode solution at 0.2-Hz stimulation. Resting [Ca2+]i rose within 50 min (group I) but stabilized in the 50- to 100-min period (group II). All preparations from group I (n = 5) resumed contraction in the recovery period but in group II (n = 10) 70% failed to recover, and [Ca2+]i remained elevated compared with those that recovered. An extracellular pH of 6.2, resulting in similar pHi, from onset of rigor development (group III) led to only a modest rise in [Ca2+]i during the 100-min rigor period, and all preparations resumed contraction after approximately 3 min in normal medium. ATP was very low in all groups at the end of MI but was still significantly lower in group II than in groups I and III. A beneficial energy-sparing effect of low pH during the rigor phase can therefore not be excluded. We conclude that 1) the capacity of trabeculae to recover from MI depends on the time period and magnitude of the [Ca2+]i rise in the energy-depleted phase and 2) low pH in energy-depleted trabeculae protects against Ca overload, improving recovery after normalization of perfusion conditions.

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