AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 1 270-R275, Copyright © 1989 by American Physiological Society
Osmoregulation of vasopressin secretion and thirst during the estrous cycle of pigs
C. Rollin, J. Kucharczyk, J. Lemoine, D. Bichet and B. K. Tsang
University of Ottawa, Loeb Institute of Medical Research, Ottawa Civic Hospital, Ontario, Canada.
The influence of the reproductive cycle on ingestive behaviors, osmotically
induced fluid intake, and peripheral blood levels of several hormones
involved in fluid electrolyte balance was investigated in young adult
female pigs. Food, water, and salt intakes and plasma aldosterone levels
were significantly lower during estrus compared with the luteal and
follicular phases, whereas plasma sodium (PNa) was higher. Plasma renin
activity and lysine vasopressin (LVP) levels did not vary with the cycle.
Regression analyses of the relationship between plasma LVP and PNa in
unanesthetized, unstressed animals infused for 2 h with intravenous 5% NaCl
revealed no significant differences in terms of the osmotic threshold and
sensitivity of LVP release at different stages of the reproductive cycle.
In contrast, when osmotic loading was carried out with continuous access to
water, the osmotic threshold for drinking was found to be significantly
higher and the rate of drinking lower during estrus. The results indicate
that in the adult female pig the stage of the reproductive cycle has an
influence on ingestive behaviors and the osmoregulation of thirst.
Osmoregulation of vasopressin secretion, on the other hand, appears to be
independent of the estrous cycle in this species.
