Angiotensin and Na appetite of sheep
Weisinger, R.S.; Denton, D.A.; McKinley, M.J.; Muller, A.F.; Tarjan, E.
American Journal of Physiology 251(4 Pt 2): R690-R699
1986
ISSN/ISBN: 0002-9513 PMID: 3766768 Document Number: 281789
The effect of intravenous (iv; 24 mu g/h) and intracerebroventricular (ivt; 3.8 mu g/h) infusion during 1 to 2 days of angiotensin II (ANG II) on sodium intake of Na-replete and -deplete sheep (i.e., 22 h loss of parotid saliva) was observed. In Na-replete sheep with continuous access to water and 2-h daily access to 0.5 M NaCl solution, both iv and ivt ANG II caused an increase in Na intake. The increase in Na intake caused by iv or ivt ANG II was preceded by a Na deficit as a result of increased urinary Na excretion. The increase in Na intake was eliminated by the continuous return of urine. In Na-deplete sheep with continuous access to water and 2-h daily access to 0.6 M NaHCO3 solution, iv ANG II caused no change in Na loss but a small increase in Na intake during the 1st day of infusion. The ivt ANG II caused no change in Na loss or in Na intake. The iv ANG II caused a small and inconsistent increase in water intake in Na-replete sheep but did not cause any change in water intake of Na-deplete sheep. The ivt ANG II caused a large increase in water in Na-replete and -deplete sheep. In Na-replete and -deplete sheep, iv ANG II did not change cerebrospinal fluid or plasma Na or osmolality but decreased plasma K. The ivt ANG II decreased cerebrospinal fluid and plasma Na and osmolality. The results are consistent with the proposition that the ANG II-induced Na appetite in sheep is largely due to an ANG II-induced Na loss preceding the development of appetite.