Metabolic and cardiovascular adaptations in trained hypophysectomized rats

Metabolic and cardiovascular changes resulting from acute and chronic exercise were examined in male Sprague-Dawley rats assigned to sham-control or hypophysectomized groups. Two weeks after surgery, the hypophysectomized rats had decreased their maximum oxygen consumption (VO2 max) and heart rate values by 4 ml X min-1 X kg-1 and 142 beats X min-1, respectively. Twenty weeks later, hypophysectomy was associated with a 22 ml X min-1 X kg-1 decrease in VO2 max and a 215 beat X min-1 decline in their maximal heart rates when compared with sham-control means. Endurance training was responsible for the significantly higher O2 consumption values. Additionally, trained animals exhibited longer run times, higher muscle cytochrome oxidase activity, and reduced food consumption. Measurements of right atrial choline acetyltransferase (CAT) activity and [3H]quinuclidinyl benzilate (QNB) binding revealed significantly higher CAT values and fewer muscarinic receptors. However, training had no significant effect on resting blood pressure, blood pressure changes with conditions of lower body negative pressure, muscle glycogen concentrations, CAT levels and QNB binding of the left atrium and ventricular regions, or receptor density. These results indicated that many of the adaptations that are characteristic of normal populations can occur in the absence of the hormones from the pituitary gland.