Hydrocortisone and triiodothyronine regulation of malate-aspartate shuttle enzymes during postnatal development of chicken

170-175The normal endogenous level of malale-aspartale shuttle enzymes and its regulation by hydrocortisone and triiodothyronine were studied in the liver and kidney of 0-, 30- and 60-day old male Rhode Island Red (RIR) chicken. The endogenous activity of cytosolic malate dehydrogenase (c-MDH) was significantly higher in the liver or day 30 as comparcd to day 0 and 60. In contrast, mitochondrial malate dehydrogenase (m-MDH) activity decreased at day 60 in the liver. However, both c- and m-MDH had significantly lower activities at day 0, which increased sharply at day 30 and 60 in the kidney. On the other hand. activity of both cytosolic and mitochond ri al aspartate aminolransfera se (c- and m-AsAT) showed peak value al day 30 in both liver and kidney. Hydrocortisone administration induced c-MDH in the liver al all the ages studied, but did not influence the activity of the isoenzymes in the kidney whereas, it induced m-MDH in the liver at day 0 and in kidney at day 30. Administration of hydrocortisone. however, did not influence AsAT isoenzymes (c- and m-AsAT) in either of the tissues at any of the postnatal ages. Triiodothyronine induced c-MDH in the liver at all the ages whereas kidney isoenzyme was induced only at day 60. In contrast, m-MDH was induced by triiodothyronine in both liver and Kidney all day 30 and 60. Administration of triiodothyronine did not influence c-AsAT of liver and kidney at either of the ages, whereas it induced m-AsAT of only liver at day 0 and 60. These fin dings indicated a ti ssue- and age-specific express ion of the malate-spartate shuttle enzymes in chicken and difference in the regulation exerted by hydrocortisone and triiodothyronine during postnatal development or chicken.