The role of neurohypophysis in the long‐term blood pressure regulation in rats

Abstract

Evidence suggest that arginine vasopressin (AVP) may contribute to the development and/or maintenance of hypertension in humans and experimental animals. This is partially explained by the antidiuretic (increased vascular volume) and vasopressor effects (increased blood vessels resistance) of AVP. Here we propose that rats with long‐term low blood levels of AVP will cause increases in both; urine output and water intake and diminution of the mean blood pressure (MBP). Young male Wistar rats were divided in sham operated (SHAM) and neurointermediate pituitary lobectomized (NIL) (n=15 in each group). Water intake and urine output where measured once a week by placing the animals in a metabolic box. Five weeks after surgeries MBP was measured by an intra carotid catheter connected to a blood pressure transducer and a data acquisition system (BIOPAC Systems Inc.). AVP, Na+ and K+ serum levels were also measured. Results shown that as compared with SHAM group, NIL animals developed significant low AVP levels, no changes in Na+ and K+ levels and an initial increase in urine output and water intake (diabetes insipidus), to return to normality during second week. In NIL animals a significant diminution of MBP occurred: SHAM, 105±9.2 versus 65±6 mmHg of the NIL animals, p<0.001. These results suggest that neurohypophyseal AVP may be an important factor in the long‐term blood pressure regulation.