AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 4 690-R699, Copyright © 1986 by American Physiological Society
Angiotensin and Na appetite of sheep
R. S. Weisinger, D. A. Denton, M. J. McKinley, A. F. Muller and E. Tarjan
The effect of both intravenous (iv; 24 micrograms/h) and
intracerebroventricular (ivt; 3.8 micrograms/h) infusion over 1-2 days of
angiotensin II (ANG II) on Na intake of both 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 due to
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 intake in both
Na-replete and -deplete sheep. In both Na-replete and -deplete sheep, iv
ANG II did not alter cerebrospinal fluid or plasma [Na] or osmolality but
decreased plasma [K]. The ivt ANG II decreased both cerebrospinal fluid and
plasma [Na] and osmolality. The results of the present experiments 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.
