Vascular Reactivity to Angiotensin and Noradrenaline in Rats Maintained on a Sodium Free Diet or Made Hypertensive with Desoxycorticosterone Acetate and Salt (Doca/Salt)

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Abstract
The pressor response to angiotensin II (ATII) and to noradrenaline (NA) [norepinephrine], the response of vascular beds (hind-quarter and kidney) isolated and perfused with Krebs'' solution and the contractions of strips of thoracic aortae, portal veins to the same agents were measured in animals and organs taken from rats maintained on a Na free diet or made hypertensive with DOCA[deoxycorticosterone acetate]/salt and in several groups of controls. The myotropic effects of ATII and of 5HT [5-hydroxytryptamine] were compared in stomach fundi. The purpose was to determine how a reduction or an increase of total body Na and the associated changes of renin production can influence the vascular response to angiotensin and to catecholamines. Reduction of Na in the diet was accompanied by no changes or a decrease of the responses of isolated vascular beds and tissues to ATII and NA; the pressor effect of ATII was also reduced and that of NA was definitely increased. Treatment with DOCA/salt and the resulting hypertension were accompanied by an increased vascular response to ATII in vivo, to ATII and NA in the isolated hindquarter; the other preparations (the perfused kidney, the thoracic aorta and the stomach fundus) showed a decreased response specific for ATII (in the kidney and the aorta) and to both ATII and 5HT (in the stomach). The responses of the portal veing to ATII and NA were unchanged. The results are discussed in relation to the changes of renin production occurring in the 2 experimental conditions and with respect to the various mechanisms currently considered for explaining the changes of vascular reactivity in hypertension.