AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 2 240-R249, Copyright © 1992 by American Physiological Society

ARTICLES

Relationship between blood O2 content and catecholamine levels during hypoxia in rainbow trout and American eel

S. F. Perry and S. D. Reid
Department of Biology, University of Ottawa, Ontario, Canada.

Plasma catecholamine levels and arterial blood respiratory variables were monitored in rainbow trout (Oncorhynchus mykiss) and American eel (Anguilla rostrata) acutely exposed (30 min) to graded levels of external hypoxia [water PO2 (PWO2) 20-90 Torr]. The experiments were designed to evaluate the factors controlling catecholamine mobilization in hypoxic fish and to elucidate the basis of marked interspecific differences. In trout, plasma catecholamine levels were unchanged when PWO2 remained above 50 Torr but increased markedly when PWO2 was lowered below this value; the predominant catecholamine released into the circulation was epinephrine. In eel, there was no such obvious PWO2 threshold for catecholamine release although plasma levels were consistently elevated above baseline only at PWO2 less than 35 Torr. The magnitude of the catecholamine release in eel was approximately an order of magnitude less than in trout. Unlike in trout, there was no increase in the plasma epinephrine-to-norepinephrine concentration ratio. During hypoxia, the relationship between arterial blood PO2 (PaO2) and PWO2 was similar in both species and thus could not explain the differences in the PWO2 thresholds for catecholamine release. In trout, the calculated PaO2 thresholds for catecholamine release were 25.3 (epinephrine) and 20.5 Torr (norepinephrine) whereas in eel the corresponding values were 12.5 and 11.6 Torr, respectively. These PaO2 thresholds were in good agreement with the in vivo values for PaO2 at half-maximal hemoglobin (Hb)-O2 saturation (P50) for trout and eel blood of 22.9 and 11.1 Torr, respectively. Thus both species displayed essentially equivalent catecholamine release thresholds when expressed in terms of arterial blood O2 content corresponding to approximately 45-60% Hb-O2 saturation.

This article has been cited by other articles:

				P. K. Battiprolu, K. J. Harmon, and K. J. Rodnick Sex differences in energy metabolism and performance of teleost cardiac tissue Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2007; 292(2): R827 - R836. [Abstract] [Full Text] [PDF]

				L. M. Hanson, S. Obradovich, J. Mouniargi, and A. P. Farrell The role of adrenergic stimulation in maintaining maximum cardiac performance in rainbow trout (Oncorhynchus mykiss) during hypoxia, hyperkalemia and acidosis at 10{degrees}C J. Exp. Biol., July 1, 2006; 209(13): 2442 - 2451. [Abstract] [Full Text] [PDF]

				S. F. Perry, S. G. Reid, K. M. Gilmour, C. L. Boijink, J. M. Lopes, W. K. Milsom, and F. T. Rantin A comparison of adrenergic stress responses in three tropical teleosts exposed to acute hypoxia Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2004; 287(1): R188 - R197. [Abstract] [Full Text] [PDF]

				S. G. Reid and S. F. Perry Peripheral O2 chemoreceptors mediate humoral catecholamine secretion from fish chromaffin cells Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2003; 284(4): R990 - R999. [Abstract] [Full Text] [PDF]

				K. N. Lapner and S. F. Perry The role of angiotensin II in regulating catecholamine secretion during hypoxia in rainbow trout Oncorhynchus mykiss J. Exp. Biol., January 12, 2001; 204(23): 4169 - 4176. [Abstract] [Full Text] [PDF]