AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 2 274-R283, Copyright © 1988 by American Physiological Society
Hormonal and electrolyte responses of conscious sheep to 96 h of hypoxia
D. C. Curran-Everett, J. R. Claybaugh, K. Miki, S. K. Hong and J. A. Krasney
Department of Physiology, School of Medicine, State University of New York, Buffalo 14214.
Hypoxia alters the relationship of aldosterone secretion to plasma renin
activity. The potential role plasma electrolytes play in this modification
is not clear. This study analyzed the interrelationships among renin,
aldosterone, vasopressin (ADH), and plasma electrolytes during 96 h of
normobaric hypoxia. Eight ewes were exposed, in discrete experiments, to
hypocapnic hypoxia [arterial O2 tension (PaO2) 37-42 mmHg, arterial CO2
tension (PaCO2) 26-28 mmHg] and eucapnic hypoxia (PaO2 40-43 mmHg, PaCO2
28-31 mmHg) by N2 dilution in an environmental chamber. Urine output (24 h)
was measured, and arterial plasma samples were collected during the
normoxic control period and at 24-h intervals of hypoxia. Plasma Na+, K+,
renin, and ADH levels did not change from the normoxic values during either
hypocapnic or eucapnic hypoxia. However, urinary aldosterone excretion
[critical significance (alpha) less than 0.046] and K+ excretion (alpha
less than 0.046) decreased markedly during each type of hypoxia. All sheep
developed a pronounced negative K+ balance by 96 h of hypoxia. These data
suggest that plasma K+ concentration is preserved by movement of K+ out of
the intracellular compartment; this change in K+ distribution may inhibit
aldosterone secretion during hypoxia.
