The Reduction of the Pressor Action of Angiotensin Ii in Sodium‐deficient Conscious Sheep

Abstract

SUMMARY.The pressor effect of intravenous infusion of antiotensin II in sheep was greatly reduced by sodium deficiency. There was a similar reduction in the pressor effect of Neosynephrine, Aramine and adrenaline. The significance of this finding is discussed in the light of the proposition that angiotensin II is the aldosterone stimulating hormone.In sodium depletion catecholamines in low doses produced cardiac dysrhythmias.INTRODUGTION. The existence of an aldosterone stimulating hormone (ASH) was demonstrated by cross circulation experiments on conscious sheep using sodium deficiency of the donor as the evoking stimulus and on dogs using caval constriction of the donor as the evoking stimulus (Denton et al, 1959;Yankopoulos et al, 1959). Genest et al (1960) showed that intravenous infusion of angiotensin II in man caused an increased urinary excretion of aldosterone. Laragh et al. (1960), using the isotope dilution method, demonstrated that intravenous infusion of angiotensin II increased aldosterone secretion. Experiments in this laboratory have confirmed the aldosterone stimulating effects of angiotensin II and, in addition, it has been shovvTi by infusion of angiotensin into the adrenal arterial blood supply to the transplanted adrenal of sheep that the action is directly upon the adrenal cortex and not mediated by other mechanisms (BlairWest ef aZ., 1962).The work of Davis et al (1961aDavis et al ( , 1961b, Garpenter et al. (1961) and Ganong and Mulrow (1961) has implicated the kidney in the mechanism of aldosterone regulation and suggests that the renin-angiotensin II system may be the efferent humoral element (ASH). It has been observed that the five-to tenfold rise of aldosterone secretion which occurs with onset of sodium deficiency

Relationship between Sodium Intake and Norepinephrine Storage during the Development of Experimental Hypertension

“…The vascular reactivity to catecholamines has been found to increase in DOCA and sodium hypertension (15)(16)(17) as well as in by guest on May 11, 2018 http://circres.ahajournals.org/ Downloaded from other forms of hypertension (15)(16)(17)(18)(19)(20), and to decrease during sodium deprivation (21,22) and after treatment by natriuretic agents (20,23,24). It is not known to what extent the subcellular distribution of norepinephrine may be related to the state of vascular reactivity, but in these conditions it seems that the change in responsiveness could be associated with changes in subcellular distribution of the catecholamine.…”

The Effect of Corticotrophin (Acth) Administration on the Pressor Action of Angiotensin Ii, Noradrenaline and Tyramine in Sheep

“…It has been shown previously that the pressor response to angiotensin I1 in sheep is markedly diminished after sodium depletion (Blair-West et al, 1963, 1972 and, therefore, the effect of sodium depletion on the pressor responses of these three agonists was determined to validate the randomized drug administration protocol.…”

Aldosterone metabolism in pregnant ewes and fetal and newborn lambs

“…Although breed effect on plasma aldosterone levels has not been reported, plasma aldosterone was isolated in Tadmit ewes by thin-layer and paper chromatographies (Boulfekhar, 1978) ; we used only paper chromatography for our plasma aldosterone measurement. Furthermore, Na and K intake greatly influences plasma aldosterone levels in sheep (Blair-West et al, 1963). There are no data on Na and K intake in Tadmit ewes (Boulfekhar, 1978), although plasma Na and K levels did not vary significantly during the experimental period (Boulfekhar, 1978).…”