Chronic and acute effects of thyrotropin on phosphatidylinositol turnover in cultured porcine thyroid cells.
The 32P incorporation into phospholipids of isolated porcine thyroid cells, cultured for 1-4 days, has been studied in subsequent 2-h incubations. Along with culture ageing, decreased 32P incorporation into total phospholipid of control cells was observed. The presence of 40 munits/ml TSH during the 2 h incubation yielded a relative increase in labelling of phosphatidylinositol, named 'acute phospholipid effect'. A chronic treatment of the cells with TSH concentration ranging from 0.1 to 10 munits/ml ensured the maintenance of a high turnover rate of total phospholipids. The analysis of individual phospholipids revealed that 1-day culture cells in the presence of 0.1 munits/ml TSH presented a strong increase of phosphatidylinositol labelling. This 'chronic phospholipid effect' of TSH can be reproduced by a chronic treatment with dibutyryl cyclic AMP (10(-3)M) or prostaglandin E2 (10(-6)M), which did not evoke a classical phospholipid effect in a 2 h incubation. If TSH (40 munits/ml) is added to the cells in a 2 h incubation, control cells show the classical phospholipid effect whereas cells chronically treated with TSH, dibutyryl cyclic AMP or prostaglandin E2 presented a 'reverse phospholipid effect' i.e. a relative decrease in phosphatidylinositol labelling. 10(-4)M cycloheximide presence during the last 12 h of culture prevented the establishment of the 'chronic phospholipid effect' and of its consequence, 'the reverse phospholipid effect'. On the basis of these results a scheme is proposed in keeping with current hypotheses concerning phosphatidylinositol metabolism.
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D015237:Dinoprost; D015232:Dinoprostone; D007700:Kinetics; D010716:Phosphatidylinositols / Q000378:metabolism*; D011458:Prostaglandins E / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology; D013552:Swine; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
D010716:Phosphatidylinositols; D011458:Prostaglandins E; D011460:Prostaglandins F; D003994:Bucladesine; D013972:Thyrotropin; D015237:Dinoprost; D000242:Cyclic AMP; D015232:Dinoprostone