A comparative study on the steroidogenic response due to training and ACTH treatment in the adrenal cortex of the male rat

The aim of this study was to ascertain the effects of training and ACTH administration on the steroidogenic in vitro response in the adrenal cortex of the rat when the tissue was incubated with ACTH. ACTH in vivo treatment resulted in a highly significant increase in the steroidogenic response (P less than 0.001) whereas training as such caused only a slight but insignificant increase in the steroidogenic responsiveness (P greater than 0.05). Training furthermore strongly suppressed the ACTH in vivo induced response (P less than 0.001). ACTH as such revealed the smallest effect on adrenal mass but the biggest effect on the steroidogenic response. It would seem that long term exercise resulted in an overall increase in the mass and size of the adrenal glands by either increasing the size of existing cells or by increasing the number of cells or both. The latter exercise-induced proliferation of adrenal tissue may involve an adaptive mechanism whereby larger total quantities of adrenal tissue of lowered steroidogenic efficiencies (on a mass basis) are produced in order to meet the stress resulting from the training program.