THE EFFICIENCY OF OXIDATIVE PHOSPHORYLATION IN MITOCHONDRIA FROM DIABETIC RATS

Abstract

Considerable evidence has accumulated which indicates that insulin plays an important rBle in phosphate metabolism (1, 2).A number of workers have postulated that insulin has as its primary function the regulation of the efficiency of oxidative phosphorylation.In attempts to test this hypothesis, Goranson and Erulkar (3) observed that tissues from alloxan-diabetic rats appear to fix phosphate less efficiently than do those from normal animals, and Polis et al. ( 4) reported that insulin added in vitro increases phosphate fixation in aged preparations from normal rats.When P:O ratios' are computed from their data, however, it is revealed that t.he former workers (3) obtained ratios between 0.03 and 0.2 and the latter (4) between 0.2 and 1.6.Since presently attainable P:O ratios are 2 to 100 times greater than these, the effects that were observed are difficult to interpret and have questionable relevance to the problem of insulin action.Judah and Williams-Ashman (5) were unable to detect significant alterations in P:O ratios when insulin was added in vitro to "cyclophorase" preparations from normal animals.Methods are now available for the isolation of mitochondria of high phosphorylating ability (6).By the use of such mitochondria from liver, the P:O ratios for certain one-and two-step oxidative reactions have been measured for both normal and alloxan-diabetic rats.No differences which could be ascribed to insulin deficiency were detected. * This investigation