Humoral factors may mediate increased rat hindquarter blood flow in portal hypertension.

Chronic portal hypertension is associated with systemic hypotension and reduced peripheral vascular resistance. Although it is well established that splanchnic and renal vascular resistances are reduced, the contribution of possible alterations in skeletal muscle hemodynamics in portal hypertension is unknown. The present study was designed to determine if skeletal muscle vascular resistance was reduced and blood flow increased in portal hypertensive rats. In portal hypertensive animals, hind-quarter blood flow was significantly increased while vascular resistance was significantly reduced. The fall in resistance in the portal hypertensive animals was associated with an increase in the capillary filtration coefficient, suggesting that an increase in functional exchange vessel surface area occurred. Cross perfusion of control hindquarters with portal hypertensive blood resulted in a 38% reduction in hindquarter vascular resistance. Raising the plasma glucagon concentration to levels reported in portal hypertensive animals resulted in no change in blood flow or vascular resistance in control hindquarters. Skeletal muscle vascular sensitivity to norepinephrine was assessed by constructing dose-response curves in control and portal hypertensive animals. Mean ED50 values were not different. The results of these studies indicate that skeletal muscle vascular resistance is reduced in portal hypertension and humoral factors, but not glucagon, are primarily responsible for the skeletal muscle hyperemia associated with portal hypertension.