Effects of arginine vasopressin (AVP) deficiency on basal mean arterial blood pressure in the rat

Abstract

The role of AVP controlling the mean arterial blood pressure (MBP) in basal conditions remains unclear. We described that neurointermediate pituitary lobectomy (NIL) in rats, induced an early but transient diabetes insipidus and low MBP (8 weeks after lobectomy). To elucidate the chronological effects of NIL, we evaluated the AVP serum levels, water intake and urine output (diabetes insipidus, DI), and MBP immediately (0 to 6 hours post NIL) and 3, 15, 45 and 90 days post NIL. The renin, angiotensin II and aldosterone system (RAAS) was assessed at 3 and 45 days post NIL. Values were compared with the respective SHAM operated groups. Results: NIL caused significant and permanent AVP serum level decrease (10.6 ± 0.8 vs 2.4 ± 0.16 pg/ml (SD), SHAM vs NIL), transient DI (15‐30 days of duration) and permanent decrease of the MBP in 70% of the NIL animals (106.8 ± 3.15 vs 73.8 ± 3.2 mmHg). Hypotension was apparent 20‐30 minutes after NIL. No significant differences in the RAAS were evident.ConclusionsWe propose that in non‐stressed animals, basal serum levels of AVP are required to maintain the hydro‐electrolytic balance and MBP. Further studies are needed to explain why some animals did not develop hypotension, and to determine how cardiovascular, renal and hormone adaptive mechanisms in the NIL group support their survival.Supported by UAA‐PIFF and CONACYT, México and the Jarislowsky and L. Carr‐Harris Foundations