Collateral hemodynamic changes during postprandial hyperemia in portal hypertensive rats

Abstract

The aim of this study was to examine the effect of postprandial splanchnic hyperemia on collateral blood flow and pressure in portal hypertensive rats (3 weeks; partial portal vein ligated rats). Pulsed-Doppler flowmeters were implanted around both the splenorenal shunt (SRS) (a large collateral vessel that develops in the portal hypertensive rat 3 or 4 days after the induction of portal hypertension) and in the superior mesenteric artery (SMA, N==8). Changes in SRS and SMA flow were measured after a standard meal gavage in unanesthetized and unrestrained conditions. Percent change in SRS flow from baseline after gavage with a standard liquid meal was significantly greater than that after gavage with an empty tube (peak, 27.1 ::!:2.9% vs. 9.4::!:2.0%; overall, 12.2::!:2.5% vs -4.4::!:2.1 %, respectively)(p$0.OO5). The percent increase in SRS flow after gavage was not significantly different than that in SMA flow. In order to study further the significance of blood flow increase in the SRS collateral, in a separate group of anesthetized rats (Ketamine 140 mglKg) we increased the blood flow by progressively expanding the plasma volume with 3 different IV bolus of NIS ( 1 , 2 or 4 ml) The SRS blood flow increases was highly significant in each case (l6.9::!:1.0%, 27.l::!:4.7% and 65.8::!:4.8%). SRS pressure was measured in an additional group of portal hypertensive anesthetized rats (N == 22) by introducing a 23gauge needle connected to a pressure transducer into the SRS collateral. Bolus intravenous injection of 1,2 or4 mL of saline induced an increased in SRS pressure of Il.9::!:2.1 %, 12.5::!: 1.9% and 42.6::!:4.0%, respectively. These results demonstrate that postprandial splanchnic hyperemia and blood volume expansion increases collateral blood flow and that collateral pressure rises with increases in flow. This finding indicates that a liquid meal of 4.5 ml in volume (0.443 Cal/ml) increases blood flow and pressure significantly in the collateral circulation.