Histamine Evokes Greater Increases in Phosphatidylinositol Metabolism and Catecholamine Secretion in Epinephrine-Containing than in Norepinephrine-Containing Chromaffin Cells

Abstract: Chromaffin cells have H₁ histamine receptors. Histamine, acting at these receptors, increases the metabolism of inositol-containing phospholipids and stimulates catecholamine secretion from Chromaffin cells. We have investigated the effects of histamine and other agents on the accumulation of inositol monophosphate (InsP₁) and catecholamine secretion in purified cultures of norepinephrine-containing and epinephrine-containing bovine Chromaffin cells. Histamine-stimulated InsP, accumulation in epinephrine cells was three times greater than that in norepinephrine cells. In contrast, bradykinin caused roughly equivalent increases in InsP¹ accumulation in the two Chromaffin cell subtypes. Histamine-stimulated catecholamine secretion was also greater in epinephrine cells than in norepinephrine cells, whereas high K⁺, bradykinin, phorbol 12, 13-dibutyrate, and angiotensin II all caused greater secretion from norepinephrine cells than from epinephrine cells. The density of H₁ receptors in epinephrine cells was approximately three times greater than that in norepinephrine cells. The greater density of H₁ receptors on epinephrine cells may account for the greater effects of histamine on InsP₁ accumulation and catecholamine secretion in these cells.