Effect of chronic and progressive increase of portal venous pressure on renal handling of water and electrolytes in rats.

Systemic and splanchnic hemodynamics and the changes in renal function induced by saline infusion (3% body weight) were studied in rats with a chronic and progressive model of portal hypertension (CPH) and in a control group. CPH rats showed a hyperdynamic circulatory status with increased cardiac output, decreased total peripheral resistances, and decreased portal inflow. Portal hypertension was accompanied by intrahepatic hypertension. Clearance studies revealed that in basal conditions CPH rats showed lower glomerular filtration rate (GFR), renal plasma flow (RPF), urinary flow, and potassium excretion than control rats, while the difference in Na and Cl excretion was not statistically significant. After saline infusion (3% body weight, 15 ml/h), differences in GFR and RPF became nonsignificant, but CPH rats showed lower Na, Cl and osmolar excretion and urinary flow than control rats. In basal conditions, plasma renin content was higher in CPH than in control rats, and decreased in both groups after volume expansion, the difference then being not statistically significant. These results demonstrate that chronic portal hypertension results in impairment of GFR, RPF and renal handling of water and electrolytes and suggest the involvement of a hepatorenal sympathetic reflex in these alterations. This reflex could be stimulated by the increase in intrahepatic pressure rather than by portal hypertension per se.