AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 1 100-R106, Copyright © 1997 by American Physiological Society

ARTICLES

Myoglobin enhances cardiac performance in antarctic icefish species that express the protein

R. Acierno, C. Agnisola, B. Tota and B. D. Sidell
Dipartimento di Biologia, Universita di Lecce, Italy.

Channichthyid icefishes of Antarctica are unique among adult vertebrates. All icefish species lack hemoglobin and red blood cells in their circulating blood. All icefishes examined to date also lack the intracellular oxygen-binding protein myoglobin (Mb) in their oxidative skeletal muscles. However, some icefish species do express Mb in their heart ventricles. It is unknown whether Mb in those species in which it is present represents an evolutionary relic or has functional significance. To address this problem, we compared mechanical performance of isolated, perfused hearts from two species of icefish in which Mb is either present (Chionodraco rastrospinosus) or is absent (Chaenocephalus aceratus). Hearts were challenged with increasing afterload (2.5-4.0 kPa) under conditions of defined basal flow (approximately 100 ml.min-1.kg-1), in both the presence and absence of 5 mM sodium nitrite, a Mb poison. Unlike hearts from C. aceratus, which were unable to maintain a constant cardiac output under pressure loading, those from C. rastrospinosus retained a constant flow up to 3.5 kPa afterload. At the upper range of power outputs, hearts of Mb-lacking C. aceratus display greater oxygen utilization than those of Mb-containing C. rastrospinosus. Poisoning of Mb significantly impaired the ability of C. rastrospinosus hearts to face pressure loading without reduction in flow, whereas those of C. aceratus were refractory to the treatment. The results strongly support a functional role for Mb in the former species.

This article has been cited by other articles:

				D. J. Small, T. Moylan, M. E. Vayda, and B. D. Sidell The myoglobin gene of the Antarctic icefish, Chaenocephalus aceratus, contains a duplicated TATAAAA sequence that interferes with transcription J. Exp. Biol., January 1, 2003; 206(1): 131 - 139. [Abstract] [Full Text] [PDF]

				S. Egginton, C. Skilbeck, L. Hoofd, J. Calvo, and I. A. Johnston Peripheral oxygen transport in skeletal muscle of Antarctic and sub-Antarctic notothenioid fish J. Exp. Biol., March 15, 2002; 205(6): 769 - 779. [Abstract] [Full Text] [PDF]