SPLENIC CONTRACTION, CATECHOLAMINE RELEASE, AND BLOOD-VOLUME REDISTRIBUTION DURING DIVING IN THE WEDDELL SEAL

Citation
We. Hurford et al., SPLENIC CONTRACTION, CATECHOLAMINE RELEASE, AND BLOOD-VOLUME REDISTRIBUTION DURING DIVING IN THE WEDDELL SEAL, Journal of applied physiology, 80(1), 1996, pp. 298-306
Citations number
34
Categorie Soggetti
Physiology
ISSN journal
87507587
Volume
80
Issue
1
Year of publication
1996
Pages
298 - 306
Database
ISI
SICI code
8750-7587(1996)80:1<298:SCCRAB>2.0.ZU;2-R
Abstract
The spleen of the Weddell seal (Leptonychotes weddelli) may contract a nd inject red blood cells (RBCs) into the peripheral circulation durin g diving, but evidence for this hypothesis is indirect. Accordingly, w e measured splenic dimensions by ultrasonography, plasma catecholamine concentrations, hemoglobin concentration, and hematocrit in five Wedd ell seals before and after intravenous epinephrine during halothane an esthesia and while awake at the surface after voluntary dives. Spleen size was reduced immediately after epinephrine injection or after the seal surfaced. Within the first 2 min after the seal surfaced, cephalo caudal splenic length was 71 +/- 2% (mean +/- SD; P < 0.05) and spleni c thickness was 71 +/- 4% (P < 0.05) of the maximal resting values. Sp lenic size increased (halftime = 6-9 min) after the seal surfaced and was inversely correlated with plasma epinephrine and norepinephrine co ncentrations. Hemoglobin concentration increased from 17.5 +/- 5.3 g/d l (measured during general anesthesia) to 21.9 +/- 3.7 g/dl (measured in the first 2 min after surfacing). At these same times, the hematocr it increased from 44 +/- 12 to 55 +/- 8%. These values decreased (half -time = 12-16 min) after the seal surfaced. We estimate 20.1 liters of RBCs were sequestered at rest, presumably in the spleen, and released either on epinephrine injection or during diving. Catecholamine relea se and splenic contraction appear to be an integral part of the volunt ary diving response of Weddell seals.