AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 3 467-R474, Copyright © 1987 by American Physiological Society
Responses of vasopressin and enkephalins to hemorrhage in adrenalectomized dogs
M. Inoue, T. Kimura, K. Matsui, K. Ota, M. Shoji, K. Iitake and K. Yoshinaga
To study responses of methionine enkephalin-like substance (MELS) and
vasopressin (AVP) to hemorrhage, plasma MELS, AVP, and catecholamine levels
and mean arterial blood pressure (MAP) and central venous pressure (CVP)
were investigated in intact and adrenalectomized dogs (n = 34) under
pentobarbital anesthesia. Plasma MELS increased significantly following a
hemorrhage-induced rise in plasma epinephrine in intact dogs (n = 6).
Plasma AVP rose concomitantly with a fall in CVP before MAP fell, but the
subsequent fall in MAP was accompanied by a further elevation in plasma AVP
concentration. In nonhemorrhaged control dogs (n = 6) these parameters did
not change during the experiment. In adrenalectomized dogs (n = 6) the
hemorrhage-induced increase in plasma MELS and AVP was significantly
attenuated despite similar decreases in MAP as in intact dogs. In
sham-operated dogs (n = 10) changes in these parameters were similar to
those in intact dogs. The differences between plasma MELS in the superior
vena cava and thoracic aorta did not change during hemorrhage in intact
dogs (n = 6), but the differences in plasma AVP rose significantly,
indicating a release of the hormone from the head. These results indicate
that MELS release elicited by hemorrhage may largely arise from the adrenal
gland and not the brain. Adrenalectomy attenuated AVP response to
hemorrhagic hypotension.
