scholarly journals The calcium ionophore A23187 is a potent stimulator of the vitamin D3-25 hydroxylase in hepatocytes isolated from normocalcaemic vitamin D-depleted rats

1988 ◽  
Vol 255 (1) ◽  
pp. 91-97 ◽  
Author(s):  
N Benbrahim ◽  
C Dubé ◽  
S Vallieres ◽  
M Gascon-Barré
Keyword(s):  
Vitamin D ◽  
Enzyme Activity ◽  
Serum Calcium ◽  
Vitamin D3 ◽  
Ionophore A23187 ◽  
Potent Stimulator ◽  
Group 2 ◽  
Group 1

The role played by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and/or by calcium on the C-25 hydroxylation of vitamin D3 (D3) was studied in hepatocytes isolated from D-depleted rats which were divided into four treatment groups: Group 1 served as controls, Group 2 received calcium gluconate, Groups 3 and 4 were infused with 1,25(OH)2D3 at 7 and 65 pmol/24 h x 7 days respectively. The treatments normalized serum calcium in all but the controls which remained hypocalcaemic, while serum 1,25(OH)2D3 remained low in Groups 1 and 2 but increased to physiologic and supraphysiologic levels in Groups 3 and 4. The data show that basal D3-25 hydroxylase activities were not significantly affected by any of the treatments. Addition of CaCl2, EGTA, or Quin-2 in vitro revealed that relative to basal values, EGTA strongly inhibited the enzyme activity in all groups (P less than 0.0001), except in G 1; Quin-2 and CaCl2 had no significant effect on the activity of the enzyme in any of the groups. Addition of 1,25(OH)2D3 or A23187 in vitro in the presence of CaCl2 revealed that 1,25(OH)2D3 did not significantly affect enzyme activity, while A23187 was found to stimulate its activity in vitamin D-depleted animals, but most specifically in Group 2 (P less than 0.001); low serum calcium (Group 1) dampened (P less than 0.01), and 1,25(OH)2D3 treatment in vivo totally blunted (P less than 0.001) the response to A23187. The data suggest that 1,25(OH)2D3 supplementation in vivo has per se little or no effect on the basal D3-25 hydroxylase activity. The data show, however, that the magnitude of the response to various challenges in vitro is greatly influenced by the conditioning in vivo of the animals. They also show that A23187 can be a potent stimulator of the enzyme activity, which allowed us to demonstrate a significant reserve for the C-25 hydroxylation of D3 which is well expressed in hepatocytes obtained from D-depleted calcium-supplemented rats.

Renal effect of vitamin D metabolites: evidence for the essential role of the 25(OH) group

1983 ◽  
Vol 244 (6) ◽  
pp. F674-F678 ◽  
Author(s):  
M. M. Friedlaender ◽  
Z. Kornberg ◽  
H. Wald ◽  
M. M. Popovtzer
Keyword(s):  
Vitamin D ◽  
Vitamin D3 ◽  
Essential Role ◽  
Fractional Excretion ◽  
Vitamin D Metabolites ◽  
Group 2 ◽  
Fractional Excretion Of Phosphate ◽  
Group 1

The effects of 1 alpha (OH)vitamin D3 [1 alpha (OH)D3] and 24,25(OH)2vitamin D3 [24,25(OH)2D3] on the phosphaturic action of parathyroid hormone (PTH) were studied in two groups of parathyroidectomized (PTX) rats. In group 1, PTX PTH-infused rats received intravenous 1 alpha (OH)D3, and in group 2, PTX PTH-infused rats received intravenous 24,25(OH)2D3. PTX PTH-infused rats served as controls. The effects of both vitamin D metabolites on renal PTH-activated adenylate cyclase (AC) were studied in vitro. In group 1, PTH increased fractional excretion of phosphate (CP/CIn) from 0.045 +/- 0.012 (+/- SE) to 0.263 +/- 0.011 (P less than 0.005). 1 alpha (OH)D3 failed to influence this response. In group 2, PTH increased CP/CIn from 0.055 +/- 0.008 to 0.289 +/- 0.027 (P less than 0.005). 24,25(OH)2D3 reduced the PTH-induced rise in CP/CIn from 0.289 +/- 0.027 to 0.192 +/- 0.021 (P less than 0.01) and decreased the urinary excretion of adenosine 3',5'-cyclic monophosphate. In vitro, 24,25(OH)2D3 blunted the PTH-activated AC, whereas 1 alpha (OH)D3 had no effect. These results show that 24,25(OH)D3, similar to two other 25(OH) metabolites of vitamin D-25(OH)vitamin D3 and 1,25(OH)2vitamin D3-suppresses the phosphaturic action of PTH, whereas 1 alpha(OH)D3, which is devoid of a 25(OH) group, lacks this effect. This suggests that a 25(OH) group is a prerequisite for the antiphosphaturic effect of vitamin D, whereas the 1 alpha (OH) group is not essential for this action.

Evidence for interference of 25(OH)vitamin D3 with phosphaturic action of glucagon

1981 ◽  
Vol 240 (4) ◽  
pp. F269-F275 ◽  
Author(s):  
M. M. Popovtzer ◽  
H. Wald
Keyword(s):  
Adenylate Cyclase ◽  
Vitamin D3 ◽  
Fractional Excretion ◽  
Camp Level ◽  
Kidney Slices ◽  
Group 3 ◽  
Camp System ◽  
Group 2 ◽  
Group 1

The effect of 25(OH)vitamin D3 [25(OH)D3] on the phosphaturic action of glucagon was studied using clearance techniques in the following groups of rats: group 1, parathyroidectomized (PTX) glucagon-infused rats receiving intravenous 25(OH)D3; group 2, PTX 25(OH)D3-pretreated rats receiving intravenous glucagon; and group 3, the thyroparathyroidectomized glucagon-infused rats receiving intravenous 25(OH)D3. The effect of 25(OH)D3 on glucagon-induced increase of cAMP in kidney slices and glucagon-activated adenylate cyclase (AC) in kidney membrane fractions was studied in vitro. In group 1, 25(OH)D3 suppressed the glucagon-induced phosphaturia by reducing fractional excretion of phosphorus (CP/CIn) from 0.175 +/- 0.02 (mean +/- SE) to 0.112 +/- 0.12 (P less than 0.05); this was associated with a reduction of urinary cAMP from 1,830 +/- 230 to 660 +/- 120 pmol/min (P less than 0.01). In group 2, pretreatment with 25(OH)D3 reduced CP/CIn from 0.221 +/- 0.025 to 0.108 +/- 0.012 (P less than 0.005). In group 3, 25(OH)D3 reduced CP/CIn from 0.165 +/- 0.012 to 0.075 +/- 0.011 (P less than 0.005). In vitro, 25(OH)D3 blunted the glucagon-induced activation of the AC/cAMP system by reducing AC from 570 +/- 30 to 325 +/- 28 pmol cAMP.mg protein-1.h-1 (P less than 0.01) and the cAMP level from 11.2 +/- 0.9 to 8.5 +/- 0.7 pmol cAMP/g wet tissue (P less than 0.05). These results show that 25(OH)D3 blunts the phosphaturic action of glucagon and suggest that this response may be mediated through suppression of the AC/cAMP system.

scholarly journals Testing the Medina embolization device in experimental aneurysms

2019 ◽  
Vol 131 (5) ◽  
pp. 1485-1493 ◽  
Author(s):  
Robert Fahed ◽  
Tim E. Darsaut ◽  
Igor Salazkin ◽  
Guylaine Gevry ◽  
Jean Raymond
Keyword(s):  
Flow Diverter ◽  
Group 3 ◽  
Group 2 ◽  
Aneurysmal Neck ◽  
Near Occlusion ◽  
Platinum Coils ◽  
Group 1

OBJECTIVEThe Medina embolization device (MED) is a novel, braided self-expanding endovascular device designed to occlude aneurysms by constructing an in situ intrasaccular flow diverter. Although a single device can be positioned at the neck of simple spherical in vitro aneurysms, the best way to occlude more complex in vivo aneurysms (using multiple MEDs or a combination of MEDs and platinum coils) is currently unknown.METHODSFifty-two aneurysms of 3 different types were created in 31 canines, yielding 48 patent aneurysms. Treatments were randomly allocated by drawing lots: group 1, MEDs alone (n = 16); group 2, MEDs plus standard platinum coils (n = 16); and group 3, control aneurysms treated with coils alone (n = 16). Angiographic results were scored and compared immediately following treatment completion and at 3 months. Specimens were photographed and the extent of neointimal closure of the aneurysmal neck scored, followed by histopathological analyses.RESULTSAngiographic scores of 0 or 1 (occlusion or near occlusion) were initially obtained in 2 of 16 (12.5%, 95% CI 1.6%–38.3%) group 1 (MEDs alone), 3 of 16 (18.7%, 95% CI 4%–45.6%) group 2 (MEDs plus coils), and 10 of 16 (62.5%, 95% CI 35.4%–84.8%) group 3 (coils alone) aneurysms (p = 0.005). At 3 months, scores of 0 or 1 were found in 11 of 16 (68.7%, 95% CI 41.3%–89.0%) group 1, 9 of 16 (56.2%, 95% CI 29.9%–80.2%) group 2, and 8 of 16 (50%, 95% CI 24.7%–75.3%) group 3 aneurysms (p = 0.82). Neointimal scores were similar for the 3 treated groups (p = 0.66).CONCLUSIONEndovascular treatment of experimental aneurysms with MEDs or MEDs and coils showed angiographic occlusion and neointimal scores at 3 months that were similar to those achieved with standard platinum coiling.

97 PRELIMINARY DESCRIPTIVE STUDY OF EQUINE PLACENTA GENERATED AFTER TRANSFER OF IN VIVO- AND IN VITRO-PRODUCED EMBRYOS

2017 ◽  
Vol 29 (1) ◽  
pp. 156 ◽  
Author(s):  
A. Lanci ◽  
J. Mariella ◽  
B. Merlo ◽  
C. Castagnetti ◽  
E. Iacono
Keyword(s):  
Embryo Transfer ◽  
Intracytoplasmic Sperm Injection ◽  
Reproductive Technologies ◽  
Control Group ◽  
Placental Development ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

Placental changes associated with artificial reproductive technologies have been described in several species, but little information is available in horses. Joy et al. (2012) reported that human placentas from intracytoplasmic sperm injection derived embryos were heavier and thicker than those produced after natural conception. Despite the most growing interest and efficiency of artificial reproductive technologies in equine species, only recently, Pozor et al. (2016) described placental abnormalities in pregnancies generated by somatic cell NT, but there are no studies on equine placenta generated by intracytoplasmic sperm injection and traditional embryo transfer. In the present preliminary study, macroscopic differences of placentas generated after transfer of in vitro- or in vivo-produced embryos were registered. Twelve Standardbred recipient mares with pregnancy generated after transfer of in vivo-derived (Group 1) and in vitro-derived (Group 2) embryos were enrolled; 10 Standardbred mares with pregnancy derived by traditional AI were included as control (Group 3). All pregnancies were physiological, and newborn foals were healthy. Mare age, parity, length of pregnancy, gross evaluation and weight of placenta, total length of umbilical cord (UC), length of UC, number of UC coils, foal sex, and weight at birth were registered. Collected data are listed in Table 1 and are expressed as mean ± standard deviation. Differences between groups were evaluated by 1-way ANOVA, and the difference in proportion of overweight placentas was evaluated with the Fisher test. The gross evaluation of placenta revealed 8/12 placentas (2/4 Group 1; 6/8 Group 2) were heavier than 11% (Madigan, 1997) due to oedema of the chorioallantois. No overweight placentas were registered in Group 3. In Group 1, 1/4 placentas had villous hypoplasia, and in Group 2, 1/8 placentas had cystic pouches on the UC. There were no significant differences among groups. However, the proportion of overweight placentas between Group 2 (6/8) and Group 3 (0/10) approached significance (P = 0.06). Although preliminary, the results of the present study suggest that production of equine embryos in vitro may lead to alterations in placental development. Several studies in cattle and sheep have suggested that alterations in the placentas of pregnancies derived from in vitro-produced embryos are related to effects of culture on epigenetic regulation. Less is known in the horse about the effects of in vitro embryo production on placental development; thus, further research in this area is necessary. Table 1. Characteristics of full-term placentas derived from AI or embryo transfer with in vivo- and in vitro-produced embryos

Effect of intracisternal antithrombin III on subarachnoid hemorrhage-induced arterial narrowing

1989 ◽  
Vol 70 (4) ◽  
pp. 599-604 ◽  
Author(s):  
Dennis G. Vollmer ◽  
Kazuhiro Hongo ◽  
Neal F. Kassell ◽  
Hisayuki Ogawa ◽  
Tetsuya Tsukahara ◽  
...  
Keyword(s):  
Basilar Artery ◽  
Antithrombin Iii ◽  
White Male ◽  
Rabbit Model ◽  
Content Type ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

✓ The ability of antithrombin III, an endogenous plasma glycoprotein, to reverse the arterial narrowing in a rabbit model of cerebral vasospasm was evaluated. The vasodilator activity of antithrombin III on rabbit arteries was first assessed in vitro using a myograph-arterial ring preparation. Antithrombin III (10 IU/ml) induced a 55.4% ± 2.66% (mean ± standard error of the mean) relaxation in basilar artery precontracted with serotonin (5-HT) in five specimens as compared with a 9.8% ± 1.6% relaxation of common carotid artery in six specimens. For in vivo analysis, 21 New Zealand White male rabbits were separated into three groups: Group 1 served as normal controls; Group 2 received a subarachnoid blood injection (SAH) and were sacrificed on Day 3 thereafter; and Group 3 animals were subjected to SAH, then received a 2-hour intracisternal infusion of antithrombin III (100 IU) in saline prior to sacrifice on Day 3. Basilar artery caliber was determined using a morphometric method to analyze perfusion-fixed arterial segments. Control basilar artery diameter in Group 1 was 0.64 ± 0.02 mm. In Group 2 a 27% reduction in arterial caliber to 0.47 ± 0.03 mm was observed by Day 3 post SAH (p < 0.0001). Group 3 animals had a mean basilar artery diameter of 0.68 ± 0.02 mm. This was significantly larger than the untreated SAH rabbits in Group 2 (p < 0.0001), but not different from control artery diameters in Group 1. The findings demonstrate that antithrombin III in saline has a significant ability to reverse delayed narrowing of the rabbit basilar artery after SAH.

scholarly journals Stigmasterol blocks cartilage degradation in rabbit model of osteoarthritis.

2012 ◽  
Vol 59 (4) ◽  
Author(s):  
Wei-Ping Chen ◽  
Chong Yu ◽  
Peng-Fei Hu ◽  
Jia-Peng Bao ◽  
Jing-Li Tang ◽  
...  
Keyword(s):  
Cruciate Ligament ◽  
Rabbit Model ◽  
Cartilage Degradation ◽  
Tissue Inhibitors Of Metalloproteinase ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Group 2 ◽  
Group 1

Stigmasterol has been shown exhibit anti-osteoarthritic properties in vitro studies. However, the in vivo effects of stigmasterol on cartilage are still unclear. This study investigated the anti-osteoarthritic properties of stigmasterol on cartilage degradation in a rabbit model of osteoarthritis (OA). Twenty rabbits underwent bilateral anterior cruciate ligament transection (ACLT) to induce OA. Five rabbits were used as normal control. Two weeks after operation, the rabbits were randomly divided into two groups. Each group of 10 rabbits received intra-articular injection with 0.3 ml of stigmasterol in left knees and vehicle in right knees, once weekly. Group 1 was killed 6 weeks after ACLT and 2 were sacrificed 9 weeks after ACLT. The knee joints were assessed by gross morphology, histology and gene expression analysis. We found that expression of genes encoding matrix metalloproteinases (MMPs) was significantly higher while tissue inhibitors of metalloproteinase (TIMP)-1 was significantly lower in the both joints of the two OA groups compared to normal controls. Stigmasterol reduced the cartilage degradation as assessed by histological analysis and markedly suppressed MMPs expression both in group 1 and group 2. Our results suggest that stigmasterol may be considered as a possible therapeutical agent in the treatment of OA.

25 DEVELOPMENTAL COMPETENCE OF CLONED BUFFALO (BUBALUS BUBALIS) EMBRYOS PRODUCED BY TRANSFECTED OR NONTRANSFECTED FIBROBLASTS TRANSFER TO ENUCLEATED OOCYTES DERIVED FROM OVUM PICK-UP AND ABATTOIR OVARIES

2015 ◽  
Vol 27 (1) ◽  
pp. 105
Author(s):  
C. Yang ◽  
J. Shang ◽  
H. Zheng ◽  
M. Chen ◽  
F. Huang ◽  
...  
Keyword(s):  
Natural Science ◽  
Fluorescent Protein ◽  
Developmental Competence ◽  
Cleavage Rate ◽  
Reconstructed Embryos ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

The objective of this study was to explore whether fibroblasts transfection and the source of oocytes – ovum pick-up (OPU) versus abattoir ovaries – affected the in vitro and in vivo developmental competence of somatic cell nuclear transferred (SCNT) embryos in buffalo. To this aim, the serum-starved ear fibroblasts were fused into enucleated oocytes derived from abattoir ovaries (Group 1) and OPU (Group 2). Furthermore, the enucleated buffalo oocytes derived from abattoir ovaries were also fused with pEGFP-N1 transfected ear fibroblasts, and the cloned embryos were enhanced green fluorescent protein (EGFP)-positive confirmed by fluorescence microscopy (Group 3). The reconstructed embryos cultured in Groups 1 to 3 were 262, 83, 120, respectively (5 replicates); and the data were analysed by one-way ANOVA (SPSS Inc., Chicago, IL, USA). As a result, the cleavage rate in Group 3 was significantly higher than that in Group 1 (75.0% v. 54.3%; P < 0.01), and the total blastocyst rate of reconstructed embryos in Group 3 (27.3%) was significantly higher than that in Group 1 (17.4%; P < 0.01) and Group 2 (24.4%; P < 0.05). The SCNT blastocysts were vitrified with 20% ethylene glycol + 20% dimethylsulfoxide + 0.5 M sucrose; the cryosurvival rates of SCNT blastocysts in the 3 groups were not different from each other (90.0%, 94.7%, 92.3%). Following culture, the cryosurvived blastocysts were transferred into synchronized local and crossbred buffaloes, with each recipient receiving 1 or 2 embryos. The pregnancy rates after transferring embryos derived from Groups 1 to 3 were not different from each other, and were 18.75% (3/16), 33.33% (4/12), and 26.67% (4/15), respectively. These results indicate that the oocytes derived from OPU can be enucleated as recipient cytoplasm and transfected fibroblast can be adopted as nuclei donor without decreasing the SCNT efficiency in buffalo.This research was supported by grants from the National Natural Science Foundation of China (31160456) and the Natural Science Foundations of China under Grant No. 0991011, No. 2011GXSFB018045).

scholarly journals Detection and in vitro and in vivo characterization of porcine circovirus DNA from a porcine-derived commercial pepsin product

2004 ◽  
Vol 85 (11) ◽  
pp. 3377-3382 ◽  
Author(s):  
M. Fenaux ◽  
T. Opriessnig ◽  
P. G. Halbur ◽  
Y. Xu ◽  
B. Potts ◽  
...  
Keyword(s):  
Porcine Circovirus Type ◽  
Human Infection ◽  
Porcine Circovirus ◽  
Specific Pathogen ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

Non-pathogenic porcine circovirus type 1 (PCV1) and pathogenic PCV2 are widespread in swine herds. In this study, the detection and characterization of PCV1 and PCV2 DNA from porcine-derived commercial pepsin are reported. The complete genomic sequences of the pepsin-derived PCV1 and PCV2 share 76 % nucleotide sequence identity with each other and 95–99 % identity with respective North American PCV1 and PCV2 isolates. However, the PCV-contaminated pepsin lacks infectivity in PK-15 cells. To further assess the infectivity of the contaminating pepsin in vivo, 16 5-week-old, specific-pathogen-free pigs were divided randomly into three groups: pigs in group 1 (n=5) were each inoculated intramuscularly and intranasally with 4 ml PBS buffer as negative controls, those in group 2 (n=6) were each inoculated with 400 mg contaminated pepsin dissolved in 4 ml PBS and those in group 3 (n=5) were each inoculated with 4×104·3 TCID50 PCV2 as positive controls. PCV2 viraemia, seroconversion and pathological lesions were detected in group 3 pigs, but not in group 1 or 2 pigs, confirming that the contaminating PCVs were non-infectious. Nevertheless, the detection of PCV DNA in a porcine-derived commercial product raises concern for potential human infection through xenotransplantation.

scholarly journals STUDY THE POTENTIAL ANTIOXIDANT EFFECT OF VITAMIN D3 SUPPLEMENTATION ON THE LEVEL OF EXTRACELLULAR SUPEROXIDE DISMUTASE IN ASTHMATIC PATIENTS

2017 ◽  
Vol 10 (7) ◽  
pp. 258 ◽  
Author(s):  
Rasha Saadi Abbas ◽  
Manal Khalid Abdulridha ◽  
Mostafa Abdalfatah Shafek
Keyword(s):  
Vitamin D ◽  
Vitamin D3 ◽  
Forced Expiratory Volume ◽  
Treatment Level ◽  
Asthmatic Patients ◽  
Vitamin D3 Supplementation ◽  
Pre Treatment ◽  
Group 2 ◽  
To Receive ◽  
Group 1

Objective: This study was designed to evaluate the potential antioxidant effect of vitamin D3 supplementation in chronic asthma patients.Methods: A total of 44 candidate patients were diagnosed with asthma allocated as Group 1 includes 20 patients assigned to receive conventional therapy for asthma and Group 2 includes 24 patients assigned to receive conventional therapy for asthma plus 2000 IU vitamin D3 tablet for 3-month period. Furthermore, 30 apparently healthy subjects were included in the study as a control group. Pulmonary function test, serum 25-hydroxy vitamin D levels, serum extracellular superoxide dismutase (SOD3) levels were measured before and after 3 months therapy.Results: The mean forced expiratory volume in 1 second (FEV1) both the measured and the percentage of predicted value showed a highly significant increase after 3 months treatment compared to pre-treatment value in both study groups (p<0.01). When compared to pre-treatment value, there was no significant increase in forced expiratory volume in one second to forced vital capacity ratio (FEV1/FVC) in Group 1 (p>0.05), nevertheless, Group 2 showed highly significant increase after 3 months (p<0.01). Approximately, 90-96% of adult asthmatic patients revealed vitamin D deficiency (<20 ng/ml). Post-treatment with adjuvant vitamin D3 therapy, 25% of patients obtained acceptable level of vitamin D sufficiency (≥30 ng/ml). After 3 months of the treatment, Group 1 patients showed a significant decrease in mean SOD3 level compared to pre-treatment level (p<0.05), while Group 2 patients showed a significant increase in mean SOD3 level compared to pre-treatment level (p<0.05).Conclusion: Most of the asthmatic patients revealed vitamin D deficiency and supplementation with vitamin D3 reduce oxidative stress burden in those patients.

scholarly journals Reduced LH sensitivity in vivo and in vitro of corpora lutea induced during anoestrus by GnRH, and during the late breeding season, in Scottish Blackface ewes

2004 ◽  
Vol 183 (3) ◽  
pp. 517-526 ◽  
Author(s):  
T A Bramley ◽  
D Stirling ◽  
G S Menzies ◽  
D T Baird
Keyword(s):  
Breeding Season ◽  
High Plasma ◽  
Corpora Lutea ◽  
Plasma Progesterone ◽  
Group 4 ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

Scottish Blackface ewes were synchronised in mid-breeding (November; group 1; n=12 ewes) or late-breeding season (March; group 2; n=16). Anoestrous ewes (May) were treated with progestagen sponges for 7 days and then given 250 ng GnRH 3-hourly for 24 h, 2-hourly for 24 h and hourly for a further 24 h (group 3; n=12). A second group of anoestrous ewes (group 4, n=19) received three bolus injections (30 μg) of GnRH at 90-min intervals without progestagen pretreatment. After ovulation, ewes were bled twice daily until slaughter (day 4 or day 12: oestrus=day 0). Mid-breeding season (group 1) and anoestrous ewes in group 3 formed ‘adequate’ corpora lutea (CL) with high plasma progesterone levels (3–4 ng/ml) maintained for at least 12 days, and responded in vivo to ovine LH (oLH) (10 μg) with a rise in plasma progesterone on day 11 (group 3, but not group 1, ewes also responded on day 3). CL minces from these ewes responded to human chorionic gonadotrophin (hCG) in vitro with a dose-dependent increase in progesterone secretion. Ewes in group 4 had a foreshortened luteal phase (8–10 days) and low plasma progesterone levels (~1 ng/ml), consistent with formation of inadequate CL. LH injection failed to induce a significant plasma progesterone increase. Furthermore, although progesterone secretion in vitro in response to maximally stimulating doses of hCG or dibutyryl cAMP (dbcAMP) was similar to that in adequate CL, the sensitivity of these CL to hCG (EC (effective concentration)50, 1 IU hCG/ml) was reduced 10-fold compared with adequate CL (EC50, 0.1 IU hCG/ml; P<0.01). Ewes that ovulated in the late breeding season (group 2) had high plasma progesterone, although levels began to decrease after day 10. Injection of oLH in vivo increased plasma progesterone. However, sensitivity to hCG in vitro (EC50, 0.5 IU hCG/ml) was intermediate between that of adequate luteal tissue (groups 1 and 3; EC50, 0.1 IU/ml) and that of group 4 ewes (EC50, 1 IU hCG/ml). Our data demonstrate a markedly reduced luteal sensitivity to LH in vivo and hCG in vitro in Scottish Blackface ewes with inadequate CL, and suggest that a similar loss of sensitivity to LH may occur in the late breeding season.

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