Effect of luminal distension on intestinal transcapillary fluid exchange.

The direct effects of luminal distension pressure on intestinal transcapillary fluid exchange were studied in isolated autoperfused cat ileum preparations. Intestinal lymph flow, lymphatic pressure, lymph-to-plasma protein concentration ratio (L/P), blood flow, and perfusion pressures were allowed to reach a steady state at different luminal distension pressures (0-40 mmHg). Luminal distension was induced using a nonabsorbable silicone solution, thereby eliminating an influence of net water absorption. At a venous outflow pressure of 0 mmHg, lymph flow and lymphatic pressure increased, whereas blood flow and L/P decreased as luminal pressure was increased. The relationship between lymph flow, blood flow, and venous pressure was acquired at luminal pressures of 0 and 20 mmHg. When luminal pressure was 0, lymph flow increased and blood flow decreased progressively with venous pressure elevation; however, when luminal pressure was 20 mmHg, lymph flow and blood flow were unaffected until pressure exceeded 20 mmHg. The results of this study indicate that luminal pressure elevation enhances transcapillary fluid exchange and imposes a "waterfall" effect on the intestinal vasculature.