Blood pressure and renal function in a novel vasopressin‐deficient, genetically hypertensive rat strain.

Abstract

SUMMARY1. Hereditary hypothalamic diabetes insipidus was introduced into the New Zealand genetically hypertensive (NZGH) rat and its normotensive substrain (NZN) by cross-breeding males with female Brattleboro diabetes insipidus (DI) rats.2. Selective breeding of the resultant DI/hypertensive (DI/H) rats on the basis of maximum systolic blood pressure and vasopressin deficiency produced animals in the F6 generation with blood pressures at 10 weeks of age higher than in DI/ normotensive rats (DI/N), but much lower than in age-matched NZGH animals. Age-matched NZN and DI/N rats had comparable blood pressures.3. Fluid turnover was far greater in DI/N and DI/H rats than in NZN and NZGH rats. Although comparable in DI/N and NZN rats, water balance (intake -urinary loss) was reduced in DI/H rats by comparison with NZGH rats.4. Sodium balance was lower in DI/N rats compared with NZN rats but did not differ between DI/H and NZGH animals. Both DI groups had lower potassium balances.5. Basal plasma vasopressin was elevated in NZGH rats compared with NZN rats, while vasopressin was undetectable in DI animals. Plasma aldosterone levels did not differ between groups, but corticosterone was lower in DI/N and DI/H rats by comparison with NZN and NZGH rats.6. Replacement of vasopressin to achieve physiological plasma hormone levels restored normal fluid management in DI animals and was associated with a modest increase in systolic blood pressure in DI/N animals, compared with sham-treated rats. A much larger increase in blood pressure was observed in AVP-treated DI/H animals, but blood pressure remained below that in NZGH rats.7. It is apparent that vasopressin may contribute to the hypertension of the NZGH rat and that it may be required from an early age. The mode of this contribution is unclear, but abnormal renal responses have been identified.

Central and peripheral effects of the peptide ANF on renal function and blood pressure in hypertensive rats.

“…ANF (0 4 ng/min) infusion was significantly reduced (Al-Barazanji & Balment, 1989). Recent reports from our laboratory indicate that vasopressin physiology is altered in the NZGH compared to NZN rats (Ashton & Balment, 1989). The absence of a diuretic response to central ANF in NZGH animals may thus reflect some abnormality in vasopressin secretion.…”

Renal, endocrine and vascular effects of atrial natriuretic peptide in a novel vasopressin‐deficient genetically hypertensive strain of rat

“…Some characteristics of these strains have been reported previously (Ashton & Balment, 1989). These animals permit the study of cardiovascular and renal function sensitivity to ANP in hypertension in the absence of the potential confounding influence of vasopressin.…”

“…This model of hypertension is associated with chronically elevated vasopressin levels (Ashton & Balment, 1989), which may contribute to the altered responsiveness of NZGH rats to ANP.…”

“…These animals permit the study of cardiovascular and renal function sensitivity to ANP in hypertension in the absence of the potential confounding influence of vasopressin. Accordingly, we can reassess the apparent hypersensitivity of the NZGH rat to the actions of ANP (Al-Barazanji & Balment, 1989), and examine the extent to which this may rely on the associated disturbance in AVP secretion in these animals (Ashton & Balment, 1989 Associates, Harrow, UK). The extraction efficiency for ANP was 83 + 1 8 % (n = 6), and the intra-assay coefficient of variation was 7 1 % (n = 9).…”

The renal and vascular effects of central angiotensin II and atrial natriuretic factor in the anaesthetized rat.

“…The separated plasma was stored at -20 'C. Following the Sep-Pak (Millipore, Waters Associates) extraction, plasma rANF was determined using a commercial rANF radioimmunoassay (Amersham International) and plasma vasopressin was measured by radioimmunoassay according to the method described by Ashton & Balment (1989). The extraction efficiency for rANF was 83 + 1-8% (n = 6) and for vasopressin was 58 + 1-6% (n = 10); no correction has been made for sample measurements.…”