In vitro stimulation by long-acting thyroid stimulator of thyroid glucose oxidation and 32P incorporation into phospholipids

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RESUMO

Long-acting thyroid stimulator (LATS) increased glucose oxidation and 32P incorporation into phospholipids in in vitro experiments with dog thyroid slices. The time course of the response was different from that obtained with thyroid-stimulating hormone (TSH), but was very similar to the delayed effect observed in vivo. During a 45 min incubation, TSH, but not LATS increased glucose oxidation, whereas in longer experiments up to 6 hr, both substances augmented 14CO2 production. Amounts of pooled human gamma globulin equivalent to LATS were inactive. Although TSH stimulated 32P incorporation into phospholipids during a 2 hr incubation, LATS was ineffective. In longer incubations, from 4½ to 8 hr, LATS did increase 32P incorporation. The stimulatory effect of LATS was not abolished by anti-TSH antibody capable of neutralizing human TSH. Effects of LATS were also obtained with beef and pig thyroid slices. In addition to stimulation of glucose oxidation in dog thyroid slices, LATS occasionally also stimulated glucose oxidation in dog spleen and liver slices. Despite a 54-fold increase in LATS concentration, a satisfactory dose-response curve could not be demonstrated when 14CO2 production was measured.

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