Effects on sheep blood pressure of treatment with angiotensin, steroids and salt.
1. Angiotensin II (AII, 0.22 microgram/min) infused for 7-14 days, into adult unanaesthetized wethers, caused a rise in blood pressure of 7 +/- 3/7 +/- 3 mmHg (mean +/- s.e.m.) from control values of 90 +/- 5/54 +/- 3 mmHg (P less than 0.05, n = 11). Cardiac output and pulse interval were not affected. A high salt intake had no effect on blood pressure, cardiac output and pulse interval, nor did it potentiate the action of AII. 2. Ethinyl oestradiol (EE, 20 mg/week) caused a small fall in systolic and diastolic pressure of 6 +/- 3/6 +/- 5 mmHg (n = 7, P less than 0.1, P less than 0.05). When AII (0.22 microgram/min) was given with EE, it still caused a significant rise in blood pressure (P less than 0.01). The synthetic progestin (1 mg of norethisterone [NE] for 8-18 days) plus a high salt diet had no effect on arterial pressure and cardiac output but pulse interval rose significantly (P less than 0.05). 3. Therefore the reduction in vascular reactivity to angiotensin seen in human pregnancy is probably not related to high levels of oestrogen. Further, NE combined with a high salt diet does not cause hypertension in sheep.
Lumbers
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School of Physiology and Pharmacology, University of New South Wales, Kensington, Sydney, Australia.
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002302:Cardiac Output / Q000187:drug effects; D004997:Ethinyl Estradiol / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009640:Norethindrone / Q000494:pharmacology*; D009919:Orchiectomy; D011674:Pulse / Q000187:drug effects; D012756:Sheep; D012965:Sodium Chloride / Q000494:pharmacology*
D000804:Angiotensin II; D004997:Ethinyl Estradiol; D012965:Sodium Chloride; D009640:Norethindrone