Effects of Arginine Vasopressin on Capillary Filtration in the Cat Ileum

The effect of local intraarterial infusion of arginine vasopressin was studied in a vascularly perfused segment of cat ileum. Systemic arterial pressure (Pa), superior mesenteric arterial pressure (Pma), superior mesenteric venous pressure (Pv), blood flow (QB) and intestinal volume (V) were continuously monitored. Intestinal lymph flow (QL), lymphatic protein clearance (LPC), isovolumetric capillary pressure (PC), capillary filtration coefficient (KF,C) and vascular resistances were also determined. A dose-response relationship was obtained for several parameters and a dosage of 17.5 mU per kg per min was chosen for more extensive study. At this level vasopressin was found to increase both systemic (Pa) and local (Pma) arterial pressures while decreasing superior mesenteric venous pressure (Pv), capillary pressure (PC) and blood flow (QB). Precapillary (Ra), postcapillary (Rv), and total (Rt) vascular resistance were all increased during the vasopressin infusion; however, a greater effect was demonstrated on the precapillary vessels as indicated by an increased pre- to postcapillary resistance ratio (Ra/Rv). Vasopressin infusion also reduced the capillary filtration coefficient(KF,C), intestinal volume (VT), lymph flow (QL) and lymphatic protein clearance (LPC). The results of this study clearly establish an effect of vasopressin on transcapillary and lymphatic volume flows in the small intestine.