EFFECT OF VITAMIN-D DEFICIENCY AND 1,25-DIHYDROXYVITAMIN-D-3 ON RAT-HEART METABOLISM

The purpose of this study was to investigate whether vitamin D-3 defic iency and 1,25-dihydroxyvitamin D-3 treatment affect some aspects of h eart metabolism in the rat. To this end, five experimental groups were studied: (1) the control group of the vitamin D-3 supplemented rats ( Group A); (2) rachitic rats (Group B); (3) rachitic rats treated with 1,25-dihydroxyvitamin D-3 (Group C); (4) rats fed a vitamin D-deficien t diet (Group D); (5) rats fed a vitamin D-deficient diet and treated with 1,25-dihydroxyvitamin D-3 (Group E). The five groups were compare d by checking in the heart some metabolic parameters, i.e. citrate con tent, and enzyme activities in cytosol and mitochondria. Citrate conte nt was higher in the heart of treated animals when compared with the c ontrol. As regards the enzymatic activities in heart mitochondria, NAD (+)-dependent isocitrate dehydrogenase remarkably decreased in Group B rats and 1,25-dihydroxyvitamin D-3 restored quite normal values. NADP (+)-dependent isocitrate dehydrogenase decreased in Group B and Group D animals, and 1,25-dihydroxyvitamin D-3 treatment was effective in re storing control values. Citochrome c oxidase activity did not change, while citrate synthase showed an increase in all the treated rats. As regards the cytosolic enzymes, fructose-6-phosphate kinase increased i n the two groups of Vitamin D-deplete rats in comparison with the cont rol. Glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate k inase showed a similar trend: an increase in all the treated animals. In heart homogenate, acylphosphatase and acid phosphatase activities w ere also determined. Acylphosphatase increased in the treated rats, wh ile acid phosphatase decreased in the rats injected with 1,25-dihydrox yvitamin D-3. These results support the hypothesis of a participation of 1,25-dihydroxyvitamin D-3 in some aspects of heart metabolism.