The Effects of Growth and Exercise on Protein Turnover and Sensitivity to Testosterone Administration in Skeletal Muscle of Prepubertal Rats
Year: 1985
Type: dissertation
Abstract: The effects of growth, exercise acclimatization (AC) and exhaustive exercise (A) on skeletal muscle protein sythesis, turnover and sensitivity to testosterone administration (T) were studied in the homogenate (HOM), mitochondria1 (MIT) and sarcoplasmic (SAR) fractions in soleus and gastrocnemius muscles of prepubescent rats. Growth effects were monitored from five to six weeks of age in sedentary animals (C5 and C6). Exercised animals were acclimatized to mild treadmill exercise for five days after which acclimatized groups (AC and ACT) rested 7 2 hours . i In order to study the acute response to exercise, two groups of animals (A.Ac and A.ACT) were sacrificed 2 4 hours ' following a run to exhaustion. Three groups of animals (C~T, ACT and A.ACT) received an intraperitoneal injection of testosterone propionate (10 mg/kg body weight) 2 4 hours prior to sacrifice. Protein turnover was assessed -in vivo using a double isotope method and protein synthesis by -in vivo uptake of radioactively labelled leucine. Protein turnover rates in both muscles fell from five to six weeks of age. Protein concentration was increased in the HOM fraction of soleus muscle. Exercise acclimatization resulted in increased HOM protein concentration and elevated succinate dehydrogenase (SDH) activity. Reduced protein synthesis and elevated rates of protein degradation suggest the onset of a detraining response in these animals. High protein turnover rates in the young animals may account for the early onset of this response. Testosterone administration to sedentary rats (C6T) resulted in reduced protein concentration and rates of synthesis. As an opposite effect was observed in both groups ACT and A.AcT it is suggested that the direction of the protein response to testosterone was mediated by prior exposure to exercise. Twenty four hours following severe exercise, mitochondria1 and sarcoplasmic protein concentration in both muscles was diminished. This is in direct contrast to usual observations in adult animals. When testosterone was administered immediately following exhaustive exercise, the changes in protein synthesis and content were reversed. Therefore it is hypothesized that testosterone is required for supression of glucocorticoid induced protein catabolism following exhaustive exercise.
Source: Summit (Simon Fraser University)
Author: Susan Malcolm
Language: English
Subfield: Nutrition and Dietetics
Field: Nursing
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2107546292