Vascular Reactivity to Angiotensin and Noradrenaline in Spontaneously and Renal Hypertensive Rats

Abstract

Vascular reactivity to angiotensin II (ATII) and noradrenaline (NA) [norepinephrine] was studied in vivo and in femoral and renal vascular beds taken from spontaneously hypertensive rats (S.H.R.) of 3 and 5 mo. of age. The stimulating effects of the same agents were measured in strips of thoracic aortae, portal veins and stomach fundi taken from S.H.R. and from renal hypertensive rats (R. H.R.) 3 wk after clamping 1 renal artery (2 kidneys hypertension). Results obtained in animals or in organs derived from the 2 groups of hypertensive rats were compared with controls of the same age or of the same weight. The pressor response to ATII is increased in S.H.R. while that of NA remains unchanged. The myotropic effects of ATII and NA are definitely increased in hindquarters, kidneys and strips of veins of S.H.R. while the responses of thoracic aortae and of stomach fundi are depressed. No changes are observed in the responses of aortae, veins or stomachs of R.H.R. compared to controls. The results are discussed and compared to those obtained in DOCA[deoxycorticosterone acetate]/salt hypertensive animals in an attempt to explain the mechanisms underlying the increased pressor effect of angiotensin in rats affected by 3 forms of experimental hypertension.