Thyroidal influence on the lactate dehydrogenase isozyme pattern in pectoralis muscle of chick embryos

Abstract

The effect of methimazole (MMI) treatment on the lactate dehydrogenase (LDH) isozyme pattern in pectoralis muscle of chick embryos was ascertained using polyacrylamide gel electrophoresis. Muscle extracts from 20-day embryos contained the five isozymes typical of most vertebrates, but 9 out of 10 extracts from 17-day embryos did not contain detectable levels of LDH 5. Muscle extracts from 20-day embryos treated with MMI for 6 to 10 days prior to death had less LDH 3, 4, and 5, compared to 20-day controls. Except for faint staining in the region of LDH 3, LDH 1 and 2 were the only isozymes detected in the extracts from 16 out of 21 MMI-treated embryos. The administration of single, low doses of thyroxine at 17 or 18 days of incubation resulted in detectable amounts of LDH 4 at 20 days in muscle from MMI-treated embryos; 7 out of the 25 muscles analyzed also had detectable amounts of LDH 5. The present report of thyroidal influence on muscle LDH isozyme pattern supports earlier observations which indicated that thyroid function is important to muscle growth and development during late embryogenesis in the chick.