Physiological factors influencing radiorubidium flux across isolated rabbit mesentery

¹ Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire

A technique is described for measuring in vitro the permeability of rabbit mesentery to Rb⁸⁶ ion. Equations for passive diffusion are adequate to describe the rubidium flux through this membrane, but unlike passage through collodion, transport through mesentery exhibits a high temperature coefficient. Mesentery reacts in ways that are analogous in some respects to the behavior of intact capillaries. For example, the permeability is increased by lowering the extracellular calcium ion concentration or the pH. Hydroxytryptamine (5-HT) also elevates the Rb⁸⁶ flux, an effect that can be reversed by salicylate but not by lysergic acid diethylamide (LSD). The nature of the transport process is discussed, and it is suggested that isolated mesentery may serve as a useful model for predicting chemical effects on capillary permeability.