AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 6 1364-R1372, Copyright © 1991 by American Physiological Society
Role of adrenal catecholamines during forced submergence in ducks
A. M. Lacombe and D. R. Jones
Department of Zoology, University of British Columbia, Vancouver, Canada.
Maximum underwater tolerance (UTmax) of chronically adrenalectomized ducks
(ADX, 5.3 +/- 0.3 min) and chronically adrenal-denervated ducks (DNX, 7.2
+/- 0.2 min) was significantly lower than sham-operated controls (SH-ADX,
10 +/- 0.8 min; SH-DNX, 12.2 +/- 0.5 min). After 4 min forced submergence,
heart rates of ADX (62 +/- 16 beats/min) and DNX (31 +/- 2 beats/min) ducks
were significantly higher than in their respective sham-operated controls
(23 +/- 3 and 17 +/- 2 beats/min), although their blood pressure was
significantly lower. Arterial partial pressure of O2, arterial O2 content,
arterial pH, and lactate levels in DNX ducks (42 +/- 2 mmHg, 4.5 +/- 0.8 ml
O2/100 ml blood, 7.233 +/- 0.016, 3.1 +/- 0.3 mM, respectively) were
significantly lower than in SH-DNX ducks after 5 min forced submergence (53
+/- 1 mmHg, 6.8 +/- 0.4 ml O2/100 ml blood, 7.301 +/- 0.007, 4.8 +/- 0.4
mM, respectively). Venous infusion of catecholamines in ADX and DNX ducks
during forced submergence significantly increased UTmax. It is suggested
that adrenal catecholamines increase tolerance to underwater submersion by
enhancing peripheral vasoconstriction, thus preserving the O2 stores for
the heart and brain. Other adrenal products could also be involved.
