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Effects of Semistarvation on Rat Liver, Kidney, and Heart Mitochondrial Function¹

Department of Physiology and Biophysics, Howard University College of Medicine, Washington, D.C. 20001

Two groups of rats were provided simultaneously with a commercial stock diet for a period of 7 days. One group was fed ad libitum (control), and the other was restricted to one-fourth of the daily intake of control animals (semistarved). Body weight declined significantly in semistarved rats whereas body weight of controls increased over the 7-day period. The following were determined in vitro on mitochondria isolated from liver, kidney, and heart tissues of both groups: substrate-stimulated and DNP-uncoupled respiratory rates; specific activities of the Krebs cycle dehydrogenases, and cytochrome c oxidase. Degradative effects of reduced food intake on mitochondrial function were observed. Uncoupled respiratory rates of liver and kidney mitochondria (using succinate as substrate) and heart mitochondria (using -ketoglutarate and pyruvate) were lower. Also lower were activities of isocitrate dehydrogenase, NADP:isocitrate dehydrogenase, transhydrogenase, succinate dehydrogenase, and cytochrome c oxidase of heart mitochondria, transhydrogenase of liver mitochondria, and isocitrate dehydrogenase and transhydrogenase of kidney mitochondria. Such decreases in enzyme activities under conditions of dietary protein deficiency might have their basis in breakdown rates exceeding synthesis rates or result from partial inactivation of existing enzyme protein. Thus, there is evidence that responses to semistarvation of such parameters of mitochondrial function may differ among various tissues. In addition, liver and kidney citrate levels were lower and heart citrate level higher with semistarvation.

KEY WORDS: • semistarvation • mitochondrial respiration • enzyme activities • pyruvate • citrate

¹ Supported by U.S. Army Research Office Grant no. DAHC 19-71-G-0022 and a grant-in-aid from the Washington Heart Association.

Manuscript received 24 June 1974.