Abstract
The uptake and release of P i and substrate anions has been examined in isolated beef heart mitochondria. Evidence is presented that these mitochondria like those from rat liver, contain a P i OH − exchanger which is sensitive to mercurials and to N-ethylmaleimide and a dicarboxylate exchanger which is capable of exchanging P i for P i, P i for dicarboxylate, and dicarboxylate for dicarboxylate. Exchange on this carrier is inhibited by mercurials and the ability of this transporter to catalyze P i for dicarboxylate exchange in either direction is quantitatively much less than is found in liver mitochondria. It is concluded that previous indications of differences in divalent anion uptake between liver and heart mitochondria are the result of this quantitative discrepancy and do not indicate that fundamental differences in anion uptake mechanism are in operation. Heart mitochondria also contain an α-keto-glutarate exchanger and a tricarboxylate exchanger with properties analogous to the transporters described for other mitochondria, but with quantitative differences apparent in various measuring systems. These studies agree, for the most part, with the conclusions of Sluse, Meijer, and Tager ( Fed. Eur. Biochem. Soc. Lett. 18, 149, 1971) using rat heart mitochondria.
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