Thyroid-stimulating hormone stimulates increases in inositol phosphates as well as cyclic AMP in the FRTL-5 rat thyroid cell line.
Studies were conducted to determine whether thyroid-stimulating hormone (TSH; thyrotropin), a hormone known to increase cytosol concentrations of cyclic AMP, also stimulates the formation of inositol phosphates in thyroid cells. TSH and noradrenaline both stimulated [3H]inositol phosphate formation in a concentration-dependent manner in the rat thyroid cell line, FRTL-5 cells, which had been prelabelled with [3H]inositol. The threshold concentration of TSH required to stimulate inositol phosphate formation was more than 20 munits/ml, which is approx. 10(3)-fold greater than that required for cyclic AMP accumulation and growth in these cells. We also demonstrate that membranes prepared from FRTL-5 cells possess a guanine nucleotide-activatable polyphosphoinositide phosphodiesterase, which suggests that activation of inositide metabolism in these cells may be coupled to receptors by the G-protein, Gp. Our findings suggest that two second-messenger systems exist to mediate the action of TSH in the thyroid.
Field
J B
JB
Department of Experimental Pathology, School of Medicine, University College of London, U.K.
Ealey
P A
PA
Marshall
N J
NJ
Cockcroft
S
S
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D013268:Stimulation, Chemical; D013403:Sugar Phosphates / Q000378:metabolism*; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*
D007295:Inositol Phosphates; D013403:Sugar Phosphates; D006160:Guanosine Triphosphate; D013972:Thyrotropin; D000242:Cyclic AMP; D009638:Norepinephrine