Abstract

Experiments were performed to evaluate the effects of the specific dopamine-1-receptor agonist, fenoldopam, on the feline intestinal microcirculation. Cranial mesenteric arterial pressure, cranial mesenteric vein pressure, cranial mesenteric vein blood flow, venous occlusion capillary pressure, pre- and postcapillary resistances, total mesenteric vascular resistance, lymph flow, lymph and plasma protein concentrations, the capillary osmotic reflection coefficient, and the capillary filtration coefficient were determined in an isolated autoperfused jejunal segment in anesthetized fasted cats during intra-arterial administration of saline or fenoldopam mesylate in saline. Fenoldopam significantly increased mean cranial mesenteric vein blood flow from 26.8 +/- 3.4 to 33.7 +/- 2.8 ml.min-1.100 g-1. This increase in blood flow was due primarily to a significant decrease in mean intestinal vascular resistance from 3.14 +/- 0.32 to 2.54 +/- 0.2 mm Hg.ml-1.min-1.100 g-1, since cranial mesenteric arterial pressure during fenoldopam infusion was not different from the value obtained during control studies. Mean capillary pressure during fenoldopam infusion (17.2 +/- 0.5 mm Hg) was significantly greater than mean capillary pressure during control studies (15.6 +/- 0.3 mm Hg). The mean lymph flow during fenoldopam infusion (0.186 +/- 0.083 g/dl) was significantly greater than the value obtained during saline infusion (0.08 +/- 0.009 g/dl). Fenoldopam infusion significantly increased the mean capillary filtration coefficient from 0.135 +/- 0.021 to 0.275 +/- 0.035 ml.min-1.100 g-1.mm Hg-1 without altering the capillary osmotic reflection coefficient. These results suggest that specific dopamine-1-receptor stimulation in the small intestine increases the perfused capillary density without altering capillary permeability.(ABSTRACT TRUNCATED AT 250 WORDS)