Autoradiographic localization of peripheral [3H]-hydergine binding sites

The anatomical distribution of the ergot derivative [3H]-hydergine (co-dergocrine mesylate) was analyzed by the use of an in vitro autoradiographic technique on frozen sections of rat heart, mesenteric and renal arteries, adrenal gland and kidney. In the heart, [3H]-hydergine was bound by atria and by myocytes of ventricles. In the arterial wall, the drug was bound primarily by the adventitia, by the adventitia-media border and by the intimal layer. The density of adventitial and adventitial-medial binding sites has an inverse relation with the diameter of mesenteric or renal vessels. In the adrenal gland, [3H]-hydergine was bound primarily by the medulla and, in lesser amounts, by the zona glomerulosa. In the kidney, the drug was localized within the arterial tree as well as in cortical tubules and in medullary collecting tubules. The above findings suggest that [3H]-hydergine is bound by various structures involved in the regulation of cardiovascular homeostasis. Interaction with these sites probably accounts for the antihypertensive action of hydergine.