Comparative effects of thyrotropin and long-acting thyroid stimulator on thyroidal intermediary metabolism: Relationship to pyridine nucleotide levels

Abstract

Both thyrotropin (TSH) and the long-acting thyroid stimulator (LATS) of Graves' disease stimulate glucose oxidation and phospholipogenesis in sheep thyroid slices. TSH (0.2–0.5 USP U./ml.) effected a 22–39 per cent mean increase in 14CO 2 production from glucose-1- 14C while LATS (2–4 MRC mU./ml.) caused a 28–32 per cent mean increase in glucose oxidation. Lesser concentrations of both stimulators (TSH, 10–50 mU./ml.; LATS, 0.5–2 MRC mU./ml.) were required for significant augmentation of 32P incorporation into thyroidal phospholipids. Varying the incubation time from 1–6 hr. did not differentially alter TSH or LATS effects on 14CO 2 production or 32P incorporation in thyroid slices. Measurement of thyroidal pyridine nucleotides (PN) under these circumstances indicates little or no correlation between stimulator-induced changes in NAD NADH or NADPH NADP ratios on the one hand and augmentation of either glucose oxidation or phospholipogenesis on the other. Although dibutyryl cyclic 3′, 5′-adenosine monophosphate mimics the effects of TSH and LATS on thyroidal glucose oxidation and phospholipogenesis, the concomitant alterations seen in PN levels (increased NADH, NADPH) were entirely unlike those seen with either stimulator. These findings confirm the dissociation between changes in thyroidal PN and augmentation of intermediary metabolism within the gland.