Thirst in the rat after ligation of the inferior vena cava: role of angiotensin II.

The role of angiotensin II in thirst states after ligation of the inferior vena cava above (CLA) or below (CLB) the origin of the renal veins as compared to sham operated controls was evaluated 24 hrs after ligation. Water intake was enhanced in CLB rats and even more so in CLA rats. Plasma angiotensin II and urea concentrations and serum osmolality were increased in CLA rats. Plasma sodium concentration and hematocrit were reduced in CLA rats, and hematocrit in CLB rats as well. Water intake in CLA rats was retarded by IV infusions of saralasin. Saralasin infusions in CLA rats resulted in a dramatic increase of plasma angiotensin II concentrations. Ligation of the inferior vena cava induces major changes in body fluid homeostasis, which are more pronounced in CLA than in CLB rats. The increase in water intake in CLA rats appears to be partly mediated by angiotensin II.