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Thermal effects on the blood respiratory properties of southern bluefin tuna (Thunnus maccoyii) at 10, 23 and 36 °C, and at 0.5 and 1.5% CO2 were investigated. A reversed temperature effect occurred as the oxygen partial pressure required for 50% haemoglobin saturation (P50) at 0.5% CO2 decreased from 2.9 kPa at 10 °C to 1.7 kPa at 23 °C (apparent heat of oxygenation, ÄH°, = + 27 kJ mol− 1). However, oxygen binding was essentially independent of temperature at warmer temperatures (P50 = 1.7–2.0 kPa from 23–36 °C at 0.5% CO2; ÄH° = − 6.5 kJ mol− 1). Hill's coefficient (nH) ranged from 1.3 to 1.6, and there was a large effect of temperature on the Bohr factor (ÄlogP50/ÄpH = − 1.6 at 10 °C and − 0.9 at 36 °C). This is the first study of whole blood to demonstrate the thermal dependence of ÄH° itself, whereby the oxygen equilibrium curve is more sensitive to temperature in the lowest thermal range examined. We suggest that the functional basis for these observations lies in the necessity to ensure a sufficient oxygen supply to all tissues, including the heart and liver, without suffering from premature or excessive oxygen unloading around the heat exchanger prior to delivery of oxygen to organs and tissues that lie efferent to the exchanger.

Item Type:	Refereed Article
Keywords:	Haemoglobin; Blood oxygen affinity; Bohr effect; Oxygen equilibrium curves; Root effect; Temperature
Research Division:	Biological Sciences
Research Group:	Physiology
Research Field:	Comparative Physiology
Objective Division:	Animal Production and Animal Primary Products
Objective Group:	Other Animal Production and Animal Primary Products
Objective Field:	Animal Welfare
Author:	Frappell, P (Professor Peter Frappell)
ID Code:	68876
Year Published:	2008
Web of Science® Times Cited:	18
Deposited By:	Zoology
Deposited On:	2011-03-29
Last Modified:	2015-02-04
Downloads:	1 View Download Statistics