The mechanism of thyrotrophin action in relation to lipid metabolism in thyroid tissue

Abstract

1. The effects of thyrotrophin in vitro on the incorporation of [¹⁴C]-glucose, -glycerol, -palmitate and -oleate into the lipids of thyroid tissue were examined. 2. Thyrotrophin increased the incorporation of these ¹⁴C-labelled precursors into phosphatidylinositol specifically. 3. Thyrotrophin also increased the proportion of ¹⁴C radioactivity from labelled glucose, glycerol, palmitate and oleate incorporated into the 1,2-diglycerides. 4. The addition of thyrotrophin to thyroid slices for 10min., after 2hr. of prelabelling with [¹⁴C]glycerol, also increased the proportion of ¹⁴C radioactivity incorporated into the 1,2-diglyceride fraction. 5. After incubation of thyroid tissue with [1−¹⁴C]palmitate, thyrotrophin caused a two- to three-fold increase in the specific radioactivity of palmitate isolated from phosphatidylinositol and 1,2-diglycerides. In contrast, the specific radioactivity of palmitate isolated from the choline and ethanolamine phosphoglycerides, 1,3-diglycerides and triglycerides was not increased by thyrotrophin.