Reduced Accumulation of3H-Norepinephrine in the Rat Heart Following Hypophysectomy

The disposition of norepinephrine (NE) in hypophysectomized rats has been investigated by labeling the neurotransmitter stores in sympathetic nerve endings with tracer doses of 3H-NE. The specific activity of cardiac NE was markedly decreased 24 hr after labeling in hypophysectomized rats. This was not the result of either decreased delivery or impaired uptake of 3H-NE since no defect in accumulationaccumulation was found 5 min after labeling. Similar but less marked changes were noted in the spleens of hypophysectomized rats, but not in the salivary glands. Since the endogenous NE concentration was elevated in the hypophysectomized animals, the increased release of tracer 3H-NE over 24 hr suggests more rapid turnover and synthesis of NE following hypophysectomy. (Endocrinology82: 175, 1968)