Influence of physical training,aortic constriction and exogenous anterior pituitary hormones on the heart weights of hypophysectomized rats

Summary Studies were conducted with hypophysectomized rats to determine the effects of chronic exercise (training), injections of exogenous hormones, aortic constrictions and combinations there of on the weight of the heart. In addition, the role of growth hormone on cardiac weight was reinvestigated. The hypophysectomized rats that were trained for 10 weeks or longer had significantly heavier heart weights than their nontrained counterparts. When daily injections of a single exogenous hormone of ACTH, GH, ICSH or TSH were made into trained and nontrained animals, there was no trained group that had significantly heavier heart weights than their control group. Rats having aortic constrictions or receiving DOCA injections also had significantly heavier heart weights than their controls. When various dosages of GH (0.2 mg to 6.0 mg) were injected daily for three weeks, no evidence was obtained that indicated that the presence of this hormone resulted in cardiac enlargement. It was concluded that under the experimental condition of this study, cardiac enlargement can occur in hypophysectomized rats when the work demands on the heart have been increased.Supported in part by funds provided by the Iowa Heart Association.