Vascular reactivity to angiotensin and noradrenaline in spontaneously and renal hypertensive rats.

Vascular reactivity to angiotensin II (ATII) and noradrenaline (NA) have been studied in vivo and in femoral and renal vascular beds taken from spontaneously hypertensive rats (S.H.R.) of 3 and 5 months of age. Moreover, the stimulating effects of the same agents have been measured in strips of thoracic aortae, portal veins and stomach fundi taken from S.G.R. and from renal hypertensive rats (R.H.R.) three weeks after clamping one renal artery (two kidneys hypertention). Results obtained in animals or in organs derived from the two groups of hypertensive rats were compared with controls of the same age or of the same weight. It was found that 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. These results are discussed and compared to those obtained in DOCA/salt hypertensive animals (8) in an attempt to explain the mechanisms underlying the increased pressor effect of angiotensin in rats affected by three forms of experimental hypertension.