The role of histamine1 and histamine2 receptors in the ethanol-induced jejunal plasma protein loss.

Histamine and other mediators have been shown to be involved in the ethanol-induced jejunal plasma protein loss. In this study we have investigated whether the histamine (H)-related component of this protein loss is mediated by H1-receptors, H2-receptors or both. Four groups of dogs (n = 12 in each) were studied. They were: untreated, H1 + H2-receptor blockade, H1-receptor blockade and H2-receptor blockade. Chlorpheniramine and ranitidine were used to block H1 and H2-receptor blockade. Chlorpheniramine and ranitidine were used to block H1 and H2-receptors respectively. In all animals, jejunal protein loss was measured over 10 min periods for 90 min. Ethanol increased protein loss in all time periods (p less than 0.001). This protein loss was depressed by H1 + H2-receptors blockade throughout 90 min (p less than 0.01). H1-receptor blockade caused a similar depression of ethanol effect but only during 20 to 40 min (p less than 0.05). In contrast, H2-receptor blockade aggravated the protein losing effect of ethanol throughout 90 min (p less than 0.01). Analyses of data tend to suggest that the ethanol-induced protein loss is mediated principally by H1-receptors, and that a complete inhibition of the histamine-related ethanol-induced protein loss can be achieved only by a simultaneous blockade of both H1 and H2-receptors, and not by H1- or H2-receptor blockade alone.