Splenic contraction, catecholamine release and blood volume
redistribution during voluntary diving in the weddell seal.
Hurford, William E., Peter W. Hochachka, Robert C. Schneider, Gregory
P. Guyton, Kevin S. Stanek, David G. Zapol, Graham C. Liggins, and
Warren M. Zapol.
Department of Anaesthesia, Massachusetts General Hospital and
Harvard Medical School, Boston, Massachusetts 02114, Department of
Zoology, University of British Columbia, Vancouver, British Columbia
V6T 2A9, Canada, Postgraduate School of Obstetrics and Gynaecology,
National Women's Hospital, Auckland, New Zealand
APStracts 2:0379A, 1995.
The spleen of the Weddell seal (Leptonychotes weddelli) may contract
and inject erythrocytes (RBCs) into the peripheral circulation during
diving, but evidence for this hypothesis is indirect. Accordingly, we
measured splenic dimensions by ultrasonography, plasma catecholamine
concentrations, hemoglobin concentration and hematocrit in five
Weddell seals, before and after intravenous epinephrine during
halothane anesthesia, and while awake at the surface following
voluntary dives. Spleen size was reduced immediately after
epinephrine injection or after surfacing. Within the first two
minutes after surfacing, cephalo-caudal splenic length was 71 +/- 2%
(mean +/- SD, P < 0.05) and splenic thickness was 71 +/- 4 % (P
< 0.05) of the maximal resting values. Splenic size increased
(t1/2 = 6 - 9 min) after surfacing and was inversely correlated with
plasma epinephrine and norepinephrine concentrations. Hemoglobin
concentration increased from 17.5 +/- 5.3 gxdl-1 (measured during
general anesthesia) to 21.9 +/- 3.7 gxdl-1 (measured in the first two
minutes after surfacing). At these same times, the hematocrit
increased from 44 +/- 12% to 55 +/- 8%. These values decreased (t1/2
= 12 - 16 min) after surfacing. We estimate 20.1 L of RBCs were
sequestered at rest, presumably in the spleen, and released either
upon epinephrine injection or during diving. Catecholamine release
and splenic contraction appear to be an integral part of the
voluntary diving response of Weddell seals.
Received 22 May 1995; accepted in final form 21 August 1995.
APS Manuscript Number A535-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 15 September 1995.