Effects of infusion of combinations of adrenocorticosteroids on systemic and regional haemodynamics in conscious sheep

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ObjectiveTo compare the cardiovascular, metabolic and endocrine responses to infusions of two combinations of adrenocorticosteroids and to determine their contribution to the haemodynamic effects of corticotrophin.MethodsThe effect of 5 day's infusion of combinations of seven corticosteroids (aldosterone, cortisol, corticosterone, 11-deoxycorticosterone, 11-deoxycortisol, 17α-hydroxyprogesterone and 17α-hydroxy-20α-dihydroprogesterone and five corticosteroids (17α-hydroxyprogesterone and 17α,20α-hydroxyprogesterone omitted) on arterial pressure, cardiac output (measured using electromagnetic flow probes) and regional blood flows (measured using transit-time flow probes) was determined in conscious sheep.ResultsCombined infusion of seven steroids increased mean arterial pressure from 79±2 to 91±2 mmHg (day 5). Cardiac output increased from 5.42±0.22 to 6.55±0.41 l/min owing to an increase in stroke volume. Mesenteric conductance fell from 6.3±0.4 to 5.4±0.5 ml/min per mmHg, and renal conductance increased from 3.1±0.1 to 4.0±0.1 ml/min per mmHg, resulting in no change in total peripheral conductance. There were only minor effects on the coronary and iliac vascular beds. Infusion of five steroids caused similar changes in mean arterial pressure (from 78±1 to 89±2 mmHg on day 5), cardiac output and regional blood flows. The cardiovascular, fluid, electrolyte and endocrine responses to both steroid treatments were similar to those with corticotrophin.ConclusionsInfusion of combinations of seven or five adrenocortical steroids reproduced the cardiovascular actions of corticotrophin, namely increases in arterial pressure, and cardiac output, mesenteric vasoconstriction and renal vasodilation. This contrasts with previous studies in which only an infusion of steroids including 17α-hydroxyprogesterone and 17α,20α-OHP reproduced the pressor effect of corticotrophin fully, possibly because in these sheep, as has been proposed to be the case in humans, the dose–response curves for the hypertensinogenic, mineralocorticoid and glucocorticoid actions overlap.

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