Growth effects of electrically stimulated contraction on adult feline cardiocytes in primary culture

1995 ◽  
Vol 268 (6) ◽  
pp. H2495-H2504 ◽  
Author(s):  
S. Kato ◽  
C. T. Ivester ◽  
G. Cooper ◽  
M. R. Zile ◽  
P. J. McDermott

The purpose of this study was to determine effects of long-term electrical stimulation of cardiocyte contraction on protein synthesis rates and total protein content. Adult feline cardiocytes were plated on laminin-coated culture trays and maintained in a serum-free medium consisting of M199 supplemented with ascorbate, bovine serum albumin, creatine, carnitine, taurine, and 10(-7) M recombinant insulin. Cardiocytes were electrically stimulated to contract with use of continuous electrical pulses of alternating polarity at a frequency of 1 Hz and pulse duration of 5 ms. Nonstimulated cardiocytes are normally quiescent and were used as the control group. In control quiescent cardiocytes, protein synthesis rate decreased by 14% between days 1 and 4 in culture and then remained stable through day 7. In electrically stimulated cardiocytes, protein synthesis rates increased by 19% between days 1 and 7. Protein synthesis rates were 18% higher on day 4 and 43% higher on day 7 in electrically stimulated than in quiescent cardiocytes. Protein content per cell was determined by measuring total fluorescence per cell by use of confocal microscopy of fluorescein isothiocyanate-stained cells. Electrical stimulation significantly increased cellular protein content by 52% after 7 days compared with controls. Quiescent and electrically stimulated cardiocytes remained rod shaped, retained their myofibrillar architecture, and were responsive to electrical stimulation over the 7-day period. These data demonstrated that electrically stimulated contraction of adult cardiocytes resulted in cell growth, as assessed by an increase in protein content per cell over 7 days in culture. This increase was due, at least in part, to an acceleration of steady-state protein synthesis rates.

1992 ◽  
Vol 262 (6) ◽  
pp. C1471-C1477 ◽  
Author(s):  
J. A. Chromiak ◽  
H. H. Vandenburgh

Glucocorticoids induce rapid atrophy of fast skeletal myofibers in vivo, and either weight lifting or endurance exercise reduces this atrophy by unknown mechanisms. We examined the effects of the synthetic glucocorticoid dexamethasone (Dex) on protein turnover in tissue-cultured avian fast skeletal myofibers and determined whether repetitive mechanical stretch altered the myofiber response to Dex. In static cultures after 3-5 days, 10(-8) M Dex decreased total protein content 42-74%, total protein synthesis rates 38-56%, mean myofiber diameter 35%, myosin heavy chain (MHC) content 86%, MHC synthesis rate 44%, and fibronectin synthesis rate 29%. Repetitive 10% stretch-relaxations of the cultured myofibers for 60 s every 5 min for 3-4 days prevented 52% of the Dex-induced decrease in protein content, 42% of the decrease in total protein synthesis rate, 77% of the decrease in MHC content, 42% of the decrease in MHC synthesis rate, and 67% of the decrease in fibronectin synthesis rate. This in vitro model system will complement in vivo studies in understanding the mechanism by which mechanical activity and glucocorticoids interact to regulate skeletal muscle growth.


2006 ◽  
Vol 291 (3) ◽  
pp. E582-E586 ◽  
Author(s):  
S. Osowska ◽  
T. Duchemann ◽  
S. Walrand ◽  
A. Paillard ◽  
Y. Boirie ◽  
...  

Protein energy malnutrition is common in the elderly, especially in hospitalized patients. The development of strategies designed to correct such malnutrition is essential. Our working hypothesis was that poor response to nutrition with advancing age might be related to splanchnic sequestration of amino acids, which implies that fewer amino acids reach the systemic circulation. Administration of citrulline, which is not taken up by the liver, can offer a means of increasing whole body nitrogen availability and, hence, improve nutritional status. Thirty old (19 mo) rats were submitted to dietary restriction (50% of food intake) for 12 wk. They were randomized into three groups: 10 rats (R group) were killed and 20 others refed (90% of food intake) for 1 wk with a standard diet (NEAA group) or a citrulline-supplemented diet (Cit group). Before being killed, the rats were injected with [13C]valine, and the absolute protein synthesis rate (ASR) was measured in the tibialis using the flooding-dose method. When the rats were killed, the tibialis was removed for protein content analysis. Blood was sampled for amino acid and insulin analysis. The standard diet did not have any effect on protein synthesis or on the protein content in the muscle. Citrulline supplementation led to higher protein synthesis and protein content in muscle (117 ± 9, 120 ± 14, and 163 ± 4 mg/organ for protein content in R, NEAA, and Cit groups, P < 0.05). The ASR were 0.30 ± 0.04, 0.31 ± 0.04, and 0.56 ± 0.10 mg/h in the three groups, respectively (R and NEAA vs. Cit, P < 0.05). Insulinemia was significantly higher in the Cit group. For the first time, a realistic therapeutic approach is proposed to improve muscle protein content in muscle in frail state related to malnutrition in aging.


1998 ◽  
Vol 142 (5) ◽  
pp. 1313-1324 ◽  
Author(s):  
James L. Franklin ◽  
Eugene M. Johnson

We demonstrate that NGF couples the rate of degradation of long-lived proteins in sympathetic neurons to the rate of protein synthesis. Inhibiting protein synthesis rate by a specific percentage caused an almost equivalent percentage reduction in the degradation rate of long-lived proteins, indicating nearly 1:1 coupling between the two processes. The rate of degradation of short-lived proteins was unaffected by suppressing protein synthesis. Included in the pool of proteins that had increased half-lives when protein synthesis was inhibited were actin and tubulin. Both of these proteins, which had half-lives of several days, exhibited no degradation over a 3-d period when protein synthesis was completely suppressed. The half-lives of seven other long-lived proteins were quantified and found to increase by 84–225% when protein synthesis was completely blocked. Degradation–synthesis coupling protected cells from protein loss during periods of decreased synthesis. The rate of protein synthesis greatly decreased and coupling between degradation and synthesis was lost after removal of NGF. Uncoupling resulted in net loss of cellular protein and somatic atrophy. We propose that coupling the rate of protein degradation to that of protein synthesis is a fundamental mechanism by which neurotrophic factors maintain homeostatic control of neuronal size and perhaps growth.


1999 ◽  
Vol 276 (2) ◽  
pp. E269-E277 ◽  
Author(s):  
Douglas G. Burrin ◽  
Timothy J. Wester ◽  
Teresa A. Davis ◽  
Marta L. Fiorotto ◽  
Xiaoyan Chang

Our objective was to determine how dexamethasone (Dex) affects gastrointestinal protein metabolism and growth in neonatal pigs. Two-day-old pigs were given daily subcutaneous injections of either Dex (1 mg/kg body wt, n = 7) or saline (control, n = 6) for 7 days. In vivo protein synthesis was measured after 7 days with a bolus of [3H]phenylalanine. Tissue protein contents were measured in an initial control group of 2-day-old pigs and in control and Dex pigs after 7 days to estimate protein accretion and degradation. In control pigs, the protein accretion in the ileum was nearly sixfold greater than in the jejunum during the 7-day period. Dex nominally altered stomach growth but completely blocked the accretion of protein and DNA in the jejunum and ileum, with reduced villus height in the ileum. Dex increased the fractional protein degradation rate in the ileum (28%) and decreased the absolute protein synthesis rate in the jejunum and ileum by 17 and 21%, respectively. Dex resulted in a 40% lower total intestinal lactase activity compared with controls via reductions in both specific activity and tissue mass, especially in the ileum. Dex significantly decreased the circulating concentrations of insulin-like growth factor (IGF) I and IGF-binding protein (IGFBP)-1, -2, and -3. However, the tissue abundance of the IGF-I receptor in the stomach and ileum was greater in Dex pigs than controls. Our results suggest that Dex significantly inhibits small intestinal growth via both increased degradation and decreased synthesis of protein. Furthermore, the inhibition of intestinal growth resulted in significantly decreased lactose digestive capacity.


1988 ◽  
Vol 250 (1) ◽  
pp. 179-188 ◽  
Author(s):  
V R Preedy ◽  
L Paska ◽  
P H Sugden ◽  
P S Schofield ◽  
M C Sugden

1. We measured fractional rates of protein synthesis, capacities for protein synthesis (i.e. RNA/protein ratio) and efficiencies of protein synthesis (i.e. protein-synthesis rate relative to RNA content) in fasted (24 or 48 h) or fasted/surgically stressed female adult rats. 2. Of the 15 tissues studied, fasting caused decreases in protein content in the liver, gastrointestinal tract, heart, spleen and tibia. There was no detectable decrease in the protein content of the skeletal muscles studied. 3. Fractional rates of synthesis were not uniformly decreased by fasting. Rates in striated muscles, uterus, liver, spleen and tibia were consistently decreased, but decreases in other tissues (lung, gastrointestinal tract, kidney or brain) were inconsistent or not detectable, suggesting that, in many tissues in the mature rat, protein synthesis was not especially sensitive to fasting. 4. In fasting, the decreases in fractional synthesis rate resulted from changes in efficiency (liver and tibia) or from changes in efficiency and capacity (heart, diaphragm, plantaris and gastrocnemius). In the soleus, the main change was a decrease in capacity. 5. Surgical stress increased fractional rates of protein synthesis in diaphragm (where there were increases in both efficiency and capacity) by about 50%, in liver by about 20%, in spleen by about 40%, and possibly also in the heart. In liver and spleen, capacities were increased. In other tissues (including the skeletal muscles), the fractional rates of protein synthesis were unaffected by surgical stress.


1996 ◽  
Vol 271 (1) ◽  
pp. H29-H37 ◽  
Author(s):  
H. Wada ◽  
M. R. Zile ◽  
C. T. Ivester ◽  
G. Cooper ◽  
P. J. McDermott

The purposes of this study were 1) to determine whether angiotensin II causes growth of adult feline cardiocytes in long-term culture, 2) to compare the growth effects of angiotensin II with those resulting from electrically stimulated contraction, and 3) to determine whether the anabolic effects of contraction are exerted via the angiotensin type 1 receptor. Adult feline cardiocytes were cultured on laminin-coated trays in a serum-free medium. Cardiocytes were either electrically stimulated to contract (1 Hz, 5-ms pulse duration, alternating polarity) or were nonstimulated and quiescent. Quiescent cells were studied as controls and after treatment with angiotensin II (10(-8) M), losartan (10(-6) M; an angiotensin type 1-receptor antagonist), or angiotensin II plus losartan. Contracting cells were studied in the presence and absence of angiotensin II or losartan. In quiescent cardiocytes, angiotensin II treatment on day 7 significantly increased protein synthesis rates by 22% and protein content per cell by 17%. The effects of angiotensin II were completely blocked by losartan. Electrically stimulated contraction on days 4 and 7 in culture significantly increased protein synthesis rate by 18 and 38% and protein content per cell by 19 and 46%, respectively. Angiotensin II treatment did not further increase protein synthesis rate or protein content in contracting cardiocytes. Furthermore, losartan did not block the anabolic effects of contraction on protein synthesis rates or protein content. In conclusion, angiotensin II can exert a modest anabolic effect on adult feline cardiocytes in culture. In contracting feline cardiocytes, angiotensin II has no effect on growth. Growth caused by electrically stimulated contraction occurs more rapidly and is greater in magnitude than that caused by angiotensin II. Growth of contracting adult feline cardiocytes is not dependent on activation of the angiotensin receptor.


2011 ◽  
Vol 5 (4) ◽  
pp. 459-465 ◽  
Author(s):  
Wei-Han Chang ◽  
Jing-Jing Yan ◽  
Xin Li ◽  
Hai-Yan Guo ◽  
Yu Liu

Abstract Background: Cardiomyocyte hypertrophy is a common complication of hypertension, and is recognized as an important risk factor for cardiovascular diseases. Up to now, no study has been made on the effects of telmisartan on Ang II-induced cardiomyocyte hypertrophy. Objective: Investigate the effects of telmisartan on angiotensin II-induced cardiomyocyte hypertrophy and the phosphorylation of extracellular signal-regulated kinase (p-ERK1/2) in rat-cultured cardiomyocytes. Methods: Rat myocardial cells were cultured. Beating rates of the cardiomyocytes, cell volumes, total protein contents, protein synthesis rates, and ERK activity were measured. The phosphorylation of p-ERK1/2 was analyzed by Western blot. Results: Treatment of cultured cardiomyocytes with telmisartan inhibited angiotensin II-induced increases in cell volume, beating rate, total protein content and protein synthesis rate. Telmisartan markedly inhibited p-ERK1/2 phosphorylation in a dose- and time-dependent manner. Conclusion: Telmisartan could suppress cardiomyocyte hypertrophy induced by angiotensin II. The mechanism might be related to the inhibition of p-ERK1/2 phosphorylation.


2008 ◽  
Vol 100 (2) ◽  
pp. 306-311 ◽  
Author(s):  
Tatjana Pirman ◽  
Laurent Mosoni ◽  
Didier Rémond ◽  
Marie Claude Ribeyre ◽  
Caroline Buffière ◽  
...  

The aim of the present study was to determine whether the addition of soluble fibre in the diet affected protein metabolism in the intestinal tissues, some visceral organs and in skeletal muscle. A diet supplemented with pectin (80 g/kg) was fed to young growing rats and the effect on organ mass and protein metabolism in liver, spleen, small and large intestines and gastrocnemius muscle was monitored and compared with the control group. Protein synthesis rates were determined by measuring [13C]valine incorporation in tissue protein. In the pectin-fed rats compared with the controls, DM intake and body weight gain were reduced (9 and 20 %, respectively) as well as gastrocnemius muscle, liver and spleen weights (6, 14 and 11 %, respectively), but the intestinal tissues were increased (64 %). In the intestinal tissues all protein metabolism parameters (protein and RNA content, protein synthesis rate and translational efficiency) were increased in the pectin group. In liver the translational efficiency was also increased, whereas its protein and RNA contents were reduced in the pectin group. In gastrocnemius muscle, protein content, fractional and absolute protein synthesis rates and translational efficiency were lower in the pectin group. The stimulation of protein turnover in intestines and liver by soluble fibre such as pectins could be one of the factors that explain the decrease in muscle turnover and whole-body growth rate.


2015 ◽  
Vol 173 (1) ◽  
pp. R25-R34 ◽  
Author(s):  
Jorn Trommelen ◽  
Bart B L Groen ◽  
Henrike M Hamer ◽  
Lisette C P G M de Groot ◽  
Luc J C van Loon

BackgroundThough it is well appreciated that insulin plays an important role in the regulation of muscle protein metabolism, there is much discrepancy in the literature on the capacity of exogenous insulin administration to increase muscle protein synthesis ratesin vivoin humans.ObjectiveTo assess whether exogenous insulin administration increases muscle protein synthesis rates in young and older adults.DesignA systematic review of clinical trials was performed and the presence or absence of an increase in muscle protein synthesis rate was reported for each individual study arm. In a stepwise manner, multiple models were constructed that excluded study arms based on the following conditions: model 1, concurrent hyperaminoacidemia; model 2, insulin-induced hypoaminoacidemia; model 3, supraphysiological insulin concentrations; and model 4, older, more insulin resistant, subjects.ConclusionsFrom the presented data in the current systematic review, we conclude that: i) exogenous insulin and amino acid administration effectively increase muscle protein synthesis, but this effect is attributed to the hyperaminoacidemia; ii) exogenous insulin administered systemically induces hypoaminoacidemia which obviates any insulin-stimulatory effect on muscle protein synthesis; iii) exogenous insulin resulting in supraphysiological insulin levels exceeding 50 000 pmol/l may effectively augment muscle protein synthesis; iv) exogenous insulin may have a diminished effect on muscle protein synthesis in older adults due to age-related anabolic resistance; and v) exogenous insulin administered systemically does not increase muscle protein synthesis in healthy, young adults.


Author(s):  
J.G. Thompson ◽  
A.N.M. Sherman ◽  
N.W. Allen ◽  
L.T. McGowan ◽  
H.R. Tervit

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