Studies on the mechanism of induction of mitochondrial alpha-glycerophosphate dehydrogenase by thyroid hormone. The role of differential gene activation.

The electrophoretic characteristics of the hepatic mitochondrial cytochrome-linked alpha-glycerophosphate dehydrogenase (CGPD) induced by thyroid hormone have been examined. Mitochondria, derived from livers of C57BL/6J or BALB/cAnN mice after 3 days of L-3,5,3'-triiodothyronine (T3) (0.1 mumole) or saline administration, were extracted with Triton X-100 (5 ml/l), and the extracts subjected to alkaline discontinuous polyacrylamide gel electrophoresis. The enzyme was located on the gel by means of a histochemical stain. The migration of CGPD from T3-treated mice was identical with that from saline-treated mice in both strains, and differed from that of NAD-linked alpha-glycerophosphate dehydrogenase. This suggests that the induction does not involve the activation of a new gene for a CGPD isoenzyme that is not expressed in the basal state. In addition, enzyme from both strains of mice exhibited identical rates of migration, indicating that the enzymes from both strains are chemically identical. These conclusions must be considered tentative, pending other studies to disprove the presence of new molecular species with no change in net charge or size.