AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 2 249-R256, Copyright © 1985 by American Physiological Society
Plasma vasopressin response to peripheral administration of angiotensin in conscious rats
K. Yamaguchi, M. Koike and H. Hama
To assess a role for peripherally administered angiotensin II (ANG II) in
regulating vasopressin (antidiuretic hormone, ADH) release, the effects on
plasma ANG II and ADH of intraperitoneal injections of ANG II dissolved in
various solutions were examined in conscious rats. Plasma ANG II and ADH
were determined by radioimmunoassay using the trunk blood collected after
decapitation. Injections of 150 mM NaCl containing ANG II (6, 12, or 24
micrograms X 2 ml-1 X 100 g body wt-1) caused dose-related increases in
plasma ANG II 15 and 30 min after, but plasma ADH remained unchanged. The
lack of effect on plasma ADH of the ANG II dissolved in isotonic saline was
also confirmed in another series of experiments in which the solution with
a higher ANG II concentration was loaded by much smaller injection volume
(14.3 micrograms X 0.1 ml-1 X 100 g-1). However, when given together with
600 mM NaCl, ANG II (8 micrograms X 2 ml-1 X 100 g-1) significantly
potentiated the plasma ADH response to the vehicle at 15, 30, and 60 min,
without affecting those of plasma osmolality, sodium, and hematocrit. The
elevations of plasma ANG II and osmolality brought about by the treatment
were comparable with those previously observed in rats deprived of water
for 46 h. ANG II was without effect on the plasma ADH responses to the
intraperitoneal injections of hypertonic sucrose or mannitol solution that
did not alter plasma sodium, although these solutions were equipotent to
600 mM NaCl in augmenting plasma ADH and osmolality.(ABSTRACT TRUNCATED AT
250 WORDS)
