Organic phosphates in the red blood cells of fish

Fish are dependent on aerobic metabolism. They respond to changes in oxygen availability by a wide spectrum of compensatory and respiratory adjustment s to safeguard tissue oxygenation. Such adjustments are directed to facilit ate both oxygen uptake at the gas exchange surfaces and oxygen unloading to tissues. The importance of erythrocytic organic phosphates as regards oxyg en transfer has been recognised since 1967 when the 'dramatic' effect of 2, 3DPG on human haemoglobin was first reported. The present review examines t he appearance of all the major erythrocytic organic phosphates during the e volutionary radiation of fish. In addition, it provides examples illustrati ng qualitative and quantitative ontogenetic chang;es of organic phosphates in the red blood cell of several fish species and describes their effects o n oxygen affinities. The interaction of the organic phosphates with haemogl obins and divalent cations are also examined. Of particular interest is the regulation of erythrocytic organic phosphates according to both environmen tal and physiological conditions. (C) 2000 Elsevier Science Inc. Air rights reserved.