Uptake of 5‐Hydroxytryptamine by Mast Cell Granules in vitro

Abstract

Mast cell granules were prepared from rat peritoneal cell suspensions by freezing, thawing and differential centrifugation. The granules were electron microscopically found to be membrane free. Incubation with 5‐hydroxytryptamine (5‐HT) resulted in an uptake which was not temperature dependent, which increased with increasing 5‐HT concentrations in the medium with little tendency to saturation, which was not blocked by sodium cyanide, dinitrophenol and FCCP and which was not accelerated by adenosine triphosphate and magnesium chloride. Reserpine and guanethidine affected little the endogenous 5‐HT content but effectively de pressed the uptake of 5‐HT by the granules. ‐Amitriptyline and prenylamine lowered the endogenous 5‐HT content and in some experiments depressed the uptake to some extent. Imipramine, chlorpromazine, cocaine and g‐strophantine had little or no effect on the endogenous content or uptake of 5‐HT. It is concluded that the membrane free granules take up 5‐HT from the medium by a passive process dissimilar from the active membrane dependent uptake mechanism in intact mast cells.