Splanchnic Organ Blood Flow Research Articles

Effect of two models of portal hypertension on splanchnic organ blood flow in the rat.

Splanchnic organ blood flow and cardiac output were measured by the microsphere method in fasted rats with prehepatic portal hypertension due to portal vein stenosis, in rats with intrahepatic portal hypertension due to bile duct ligation, and in unoperated normal rats. Portal venous pressure was higher in both groups of portal hypertensive rats than in normal rats. Cardiac output was significantly higher in portal hypertensive rats than in normal rats. In rats with portal vein stenosis, splanchnic blood flow was higher than in controls. This increase was caused by increased perfusion of all organs drained by the portal vein, and by increased hepatic arterial blood flow. In rats with bile duct ligation, splanchnic blood flow was not significantly higher than in normal rats: haemoperfusion of all organs contributing to the portal circulation decreased, whereas hepatic arterial blood flow increased. As cardiac output rose similarly, the differences observed between the two types of portal hypertension depend mainly on the difference in distribution of flow within the splanchnic bed.

Acute effect of propranolol on splanchnic circulation in normal and portal hypertensive rats

Propranolol decreases portal venous pressure in patients with cirrhosis but no method is available in man to study the effect of this beta-blocker on splanchnic organ blood flow. Because in rats, the microsphere method allows evaluation of regional blood flow, the acute effect of propranolol on both splanchnic and systemic circulations was studied in normal rats and in rats with portal hypertension due to portal vein stenosis. Portal venous pressure significantly decreased during propranolol administration in normal (5.6 +/- 1.0-4.7 +/- 1.1 mm Hg; mean +/- SD) as well as in portal hypertensive rats (11.7 +/- 2.3-10.3 +/- 1.8 mm Hg). Propranolol slightly decreased cardiac output and arterial pressure in all rats. Portal tributary blood flow was significantly reduced by propranolol in normal rats (17.4 +/- 3.0-11.3 +/- 2.2 ml/min) and in portal hypertensive rats (23.7 +/- 5.0-16.6 +/- 3.3 ml/min). Accordingly vascular resistance of the different organs in the portal venous territory increased in these rats receiving propranolol. The percentage of the decrease in portal tributary blood flow was significantly more marked than the percentage of reduction in cardiac output in portal hypertensive rats but, in normal rats, these percentages were parallel. Hepatic arterial blood flow did not change or slightly increased and, consequently, hepatic arterial vascular resistance decreased. These findings further clarify the marked effects of propranolol on splanchnic circulation.

The effect of glucagon on the distribution of blood flow in the splanchnic area

The blood flow in different splanchnic organs was investigated in rats following glucagon administration utilising the 86Rb-distribution method of Sapirstein (5). There was a significant increase in blood flow to the kidneys (32 %) and to the duodenum (44 %) following 100 μg/kg glucagon. In addition, blood flow was enhanced to the liver (67 %) and to the pancreas (72 %) following 500 μg/kg glucagon. An infusion of 0.5 μg/kg/min produced only a slight increase in renal blood flow (18 %) and the arterial systematic pressure remained more or less constant after glucagon administration. The doses required for comparable effects are much higher in rats than in dogs (Kock et al. [1]). Moreover, the sensitivity of the various splanchnic organs to glucagon differs; thus, blood flow in the gastric mucosa tended to decrease, as already described by previous workers.