Affiliation:
1. Department of Arctic Biology and Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway
Abstract
Cabanac, Arnaud, Lars P. Folkow, and Arnoldus Schytte Blix.Volume capacity and contraction control of the seal spleen. J. Appl. Physiol. 82(6): 1989–1994, 1997.—Volume changes in the spleens of hooded seals ( Cystophora cristata) and harp seals ( Phoca groenlandica) were measured plethysmographically in vitro in response to epinephrine, norepinephrine, isoprenaline, phentolamine, and acetylcholine. Dilated spleens contracted forcefully within 1–3 min of α-adrenoceptor activation with 1.0–5.0 μg epinephrine/kg body mass, whereas stimulation of β-adrenoceptors and cholinergic receptors had little effect. The mass of dilated hooded seal spleens corresponded to 2–4% ( n = 7) of body mass, with volume (V; ml) relating to body mass (M; kg) as follows: V = 12.0M + 910 ( r 2 = 0.96, n = 4). Thus the spleen of a 250-kg hooded seal maximally expels 3.9 liters, or 13%, of its estimated total blood volume. Average hematocrit in splenic venous outflow from dilated spleens was 90 ± 3% ( n = 3) in hooded seals and 85% ( n = 2) in harp seals. From these data we have estimated that the aerobic diving limit of a 250-kg hooded seal increases only 105 s, at the most, if complete emptying of the spleen occurs during diving, while the corresponding estimate for a 112-kg harp seal is 80 s.
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology
Cited by
47 articles.
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