Phosphoinositides metabolism in primary culture of dog thyroid cells: effects of thyrotropin and carbachol.
Thyrotropin (TSH) and carbachol stimulated in a dose-dependent manner the accumulation of 3H-glycerophosphoinositol (GPI), 3H-inositol monophosphate (IP1), 3H-inositol bisphosphate (IP2) and 3H-inositol trisphosphate (IP3) in primary cultures of dog thyroid cells prelabeled with myo-[2-3H]inositol. TSH, 250 mU/mL, stimulated 3H-IP3 level after a 10-minute incubation while 10 mU/mL TSH increased it during a 60-minute incubation. The effect of carbachol was more rapid and greater than that of TSH. Carbachol, 100 mumol/L, elevated 3H-IP3 after a 2-minute incubation and 3H-IP3 formation was increased by as little as 1 mumol/L carbachol. TSH stimulation was observed only if the cells were deprived of TSH for 5 days before being labeled with 3H-inositol. Prolongation of the labeling period or addition of TSH, (Bu)2cAMP or carbachol during the labeling increased 3H-inositol incorporation into polyphoinositides (PIPs). When the cells were labeled without any other addition, control and TSH-stimulated 3H-IP3 levels increased in parallel with 3H-PIP levels. However, TSH or carbachol-stimulated 3H-IP3 levels did not increase in proportion to 3H-PIPs level when the cells were labeled with TSH or (Bu)2cAMP. Thus, the ratio of 3H-IP3/3H-PIPs (both control and TSH or carbachol-stimulated) decreased in the cells labeled with TSH or (Bu)2cAMP, which might reflect TSH stimulation of 3H-inositol incorporation into PIPs pool(s) that do not participate in hormone-induced hydrolysis of PIPs.(ABSTRACT TRUNCATED AT 250 WORDS)
Taguchi
M
M
Department of Medicine, St Luke's Episcopal Hospital, Houston, TX 77225-0269.
Field
J B
JB
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology*; D002478:Cells, Cultured; D004285:Dogs; D007294:Inositol / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D010716:Phosphatidylinositols / Q000378:metabolism*; D011865:Radioisotope Dilution Technique; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*; D014316:Tritium
D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D014316:Tritium; D007294:Inositol; D003994:Bucladesine; D002217:Carbachol; D013972:Thyrotropin