Endocrinology, Vol 136, 2664-2670, Copyright © 1995 by Endocrine Society

ARTICLES

Changes in the growth hormone axis due to exercise training in male and female rats: secretory and molecular responses

JA Butkus, RS Brogan, A Giustina, G Kastello, M Sothmann and WB Wehrenberg
Department of Biological and Health Sciences, University of Wisconsin, Milwaukee 53201, USA.

GH secretion is altered by exercise in humans. In an attempt to investigate the underlying mechanisms, we developed a rodent model. GH secretion was assayed in male and female rats that were sedentary (not exercised), acutely exercised, and chronically exercised. Sedentary males showed typical pulsatile GH secretion. The acutely exercised males had low GH concentrations during the exercise bout, but showed partial recovery of GH pulses during the 5.5-h postexercise period. GH secretion in the chronically exercised males was low during both the exercise and postexercise periods. Sedentary females displayed the typical pattern of GH secretion for this sex. The acutely exercised females had low GH concentrations during the exercise period; the pulsatile pattern of GH secretion did not return during the postexercise period. In contrast, the chronically exercising females had suppressed GH secretion during the exercise bout, but concentrations immediately returned to normal during the postexercise bout. The effects of exercise on GH, GH-releasing hormone (GHRH), and somatostatin messenger RNA (mRNA) levels using Northern and slot blot analyses were also determined. Acutely and chronically exercised male rats had decreased levels of GH mRNA compared to sedentary male rats. The acutely exercised female rats had increased levels of GH mRNA compared to the sedentary females, whereas the chronically exercised females had decreased levels. GHRH mRNA levels in acutely exercising male rats was decreased and in chronically exercising male rats was increased compared to those in the sedentary controls. The pattern of GHRH mRNA in female rats was the opposite of this. Somatostatin mRNA levels decreased in acutely exercised male rats and were not affected in chronically exercised male rats. This signal increased in both acute and chronically exercised female rats. These studies suggest that GH secretion is suppressed in response to exercise in the rat. This contrasts with the increase observed after exercise in humans.

This article has been cited by other articles:

				A. J. Bigbee, K. L. Gosselink, R. R. Roy, R. E. Grindeland, and V. R. Edgerton Bioassayable growth hormone release in rats in response to a single bout of treadmill exercise J Appl Physiol, December 1, 2000; 89(6): 2174 - 2178. [Abstract] [Full Text] [PDF]

				G. V. Childs, G. Unabia, and P. Wu Differential Expression of Growth Hormone Messenger Ribonucleic Acid by Somatotropes and Gonadotropes in Male and Cycling Female Rats Endocrinology, April 1, 2000; 141(4): 1560 - 1570. [Abstract] [Full Text] [PDF]

				K. L. Gosselink, R. E. Grindeland, R. R. Roy, H. Zhong, A. J. Bigbee, and V. R. Edgerton Afferent input from rat slow skeletal muscle inhibits bioassayable growth hormone release J Appl Physiol, January 1, 2000; 88(1): 142 - 148. [Abstract] [Full Text] [PDF]

				A. Giustina and J. D. Veldhuis Pathophysiology of the Neuroregulation of Growth Hormone Secretion in Experimental Animals and the Human Endocr. Rev., December 1, 1998; 19(6): 717 - 797. [Abstract] [Full Text]

				K. L. Gosselink, R. E. Grindeland, R. R. Roy, H. Zhong, A. J. Bigbee, E. J. Grossman, and V. R. Edgerton Skeletal muscle afferent regulation of bioassayable growth hormone in the rat pituitary J Appl Physiol, April 1, 1998; 84(4): 1425 - 1430. [Abstract] [Full Text] [PDF]