AJP - Regulatory, Integrative and Comparative Physiology, Vol 242, Issue 5 528-R532, Copyright © 1982 by American Physiological Society
Hormonal changes and enforced diving in the harbor seal Phoca vitulina. II. Plasma catecholamines
A. J. Hance, E. D. Robin, J. B. Halter, N. Lewiston, D. A. Robin, L. Cornell, M. Caligiuri and J. Theodore
Plasma epinephrine and norepinephrine concentrations were measured in five
harbor seals, Phoca vitulina, during a control period, during a 6-min dive,
and during a 30-min postdiving recovery period. Measurements were performed
with and without prior glucose administration. Control epinephrine
concentrations [189 +/- 118 (SD) pg/ml] and norepinephrine concentrations
(340 +/- 191 pg/ml) were similar to resting values in humans. During diving
there are dramatic increases in both epinephrine and norepinephrine
concentrations, which returned to control values by 30 min of the
postdiving recovery period. A similar pattern was found after glucose
infusion. The increased catecholamines were not the primary mechanism
responsible for arterial constriction during the dive. Persistent diving
bradycardia suggests obliteration of the chronotropic effects of
catecholamines during the dive. An unchanged stroke volume suggests
obliteration of the inotropic effects of catecholamines during the dive.
Catecholamines do not appear to be involved in postdiving hyperglycemia and
hyperglucogenemia. Neither the regulatory role of increased catecholamines
nor the physiological function of increased catecholamines was apparent
from the studies. However, dramatic increases in plasma catecholamines
during diving appear to be an important component of the hormonal response
to prolonged diving in aquatic mammals.
