5‐Hydroxytryptamine Release from Enterochromaffin Granules in vitro

Abstract

Abstract5‐Hydroxytryptamine (5‐HT) release in vitro from cow and pig enterochromaffin granule preparations was studied. An accelerated 5‐HT release from the granule fraction was caused by: elevation of temperature, freezing and thawing, dilution, increase of the pH of the incubation medium, addition of chlorpromazine, imipramine, mepyramine, segontin®, tyramine, trypsin, hydrocortisone and cortisone. In various isotonic salt and buffer solutions the amine release was faster than that in isotonic sucrose solution. A slight 5‐HT release was induced by Ca++ ions, Titriplex III®, Titriplex IV® and histamine, and an almost complete release by CuCl2, distilled water and all the detergents studied. Monoamine oxidase inhibitors (in 0.15 M phosphate buffer, pH 6.9) and MgCl2 (in 0.3 M sucrose solutions, pH 6.9) were the only chemicals that retarded amine release. The following chemicals had no effect: ACTH, thyroxine, adrenaline, noradrenaline, dihydroxyphenylalanine, tryptophan, indoleacetic acid, 3‐hydroxytyramine, acetylcholine or butyrylcholine with eserine, and guanethidine.The release of 5‐HT from enterochromaffin granules resembles in some ways amine release from platelets, mast cells or granules carrying norepinephrine but differs in others. The special features of the enterochromaffin granules are discussed.