Cytoplasmic pH in the action of insulin-like growth factor-I in cultured porcine thyroid cells.
The effects of insulin-like growth factor-I (IGF-I) on cytoplasmic pH (pHi) and [3H]thymidine incorporation were studied in primary cultures of porcine thyroid cells. IGF-I alkalinized thyroid cells and stimulated thymidine incorporation in a dose-dependent manner; the effects of IGF-I on alkalinization (the maximal rates of change of cytoplasmic pHi/min ((dpHi/dt)max)) and thymidine incorporation were observed at 2 ng/ml and were maximal at 100 ng/ml, with half-maximal stimulation at approximately 10 ng/ml. The results indicate that Na+/H+ exchange or cell alkalinization may function as a transmembrane signal transducer in the action of IGF-I on thyroid cell proliferation. Several mitogens and comitogens which activate sodium hydrogen exchange, including epidermal growth factor, platelet-derived growth factor and nerve growth factor, have been listed. Activation with IGF-I has not, however, been presented before. Thus the present study constitutes the first demonstration of IGF-I-stimulated activation of Na+/H+ exchange or cell alkalinization.
Takasu
N
N
Department of Gerontology, Endocrinology and Metabolism, School of Medicine, Shinshu University, Nagano-ken, Japan.
Komiya
I
I
Nagasawa
Y
Y
Asawa
T
T
Shimizu
Y
Y
Yamada
T
T
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism; D013552:Swine; D013936:Thymidine / Q000378:metabolism; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*
D007334:Insulin-Like Growth Factor I; D000584:Amiloride; D012964:Sodium; D013936:Thymidine