Studies on Kallikreins. IV. Enhancement of Valine Transport Across the Rat Small Intestine

Abstract

The effect of a highly purified hog pancreatic kallikrein and synthetic bradykinin on the transport of valine across the rat small intestine was examined by an in vitro experiment with the sac of everted intestine and by an in situ mesenteric perfusion experiment. The flow of valine from the mucosal to the serosal side of everted intestine was stimulated significantly by the addition of kallikrein to the mucosal fluid in a concentration of 0.1 KU/ml, while bradykinin was effective only by its addition to the serosal fluid. In a perfusion experiment, valine transport into the vascular system was enhanced significantly by intra-intestinal administration of 0.02-20 KU of kallikrein. The maximum effect was obtained with 2 KU, and the absorption of valine was 1.9 times larger than that of the control. Bradykinin infusion into the mesenteric perfusion system in concentrations of 10^-2 to 10²nM also increased the transport of valine. A bell-shaped dose-response curve, in which the maximum enhancement was achieved with 1 nM of bradykinin, was obtained similar to the case of kallikrein. This effect of kallikrein appeared soon after its administration into the intestinal lumen and usually lasted about 30 min under the present experimental conditions.