The mode of adrenal gland enlargement in the rat in response to exercise training.

Abstract

The mode of adrenal gland enlargement in the rat in response to exercise training. The mode of adrenal gland enlargement produced by physical training has been studied in normal, thyroidectomized, and thyroidectomized-hormone-treated rats. The animals were trained for 10 weeks with a program of running in motor-driven wheels at speeds and durations that approached their maximal capacities. Training produced a significant increase in adrenal weight in all groups. The DNA content, and thus cell number, of the adrenals of each trained group was higher than that of the respective sedentary control group. The weight per adrenal cell was also higher in the trained than the untrained groups. These data indicate that adrenal enlargement during training is the result of a combination of hyperplasia and hypertrophy and that this effect is not dependent upon the presence of thyroid hormone.