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Publisher Summary In an experiment described in the chapter, in four conscious water-loaded sheep, angiotensin II (AII) was infused into both carotid arteries at levels that produced low physiological A-II in the cerebral blood supply. The infusion rate was 24–32 ng/min, producing a carotid artery blood concentration of approximately 5–7 ng/100 ml. Normal sheep A-II is about 1 ng/100 ml of blood and 5–7 ng/100 ml represents levels attained in mild to moderate Na deficiency. Consecutive clearance periods were of 20 min duration. Two control periods were followed by 2–3 periods of intracarotid (ICA) A-II infusion and four recovery periods. The chapter presents data that support a physiological role for A-II in the regulation of water excretion in conscious sheep. Because identical levels of A-II infused IV did not alter BP, GFR or CH 2 O, it is suggested that the action of ICA A-II is directly upon receptors controlling vasopressin secretion located within the distribution of the carotid arteries. |
