Human growth hormone-stimulated mitogenesis of Nb2 node lymphoma cells is not mediated by an immediate acceleration of phosphoinositide metabolism.
Lactogenic hormones stimulate the mitogenesis of Nb2-11C rat lymphoma cells and this stimulation is enhanced by 12-O-tetradecanoyl phorbol ester (TPA). The effect of human growth hormone (hGH) and TPA on phosphoinositide metabolism in Nb2-11C cells was tested by measuring the incorporation of [3H]myo-inositol or 32P or measuring the breakdown of polyphosphoinositides in cells prelabeled with [3H]myo-inositol, 32P or [3H]arachidonic acid. We found that none of these processes is immediately stimulated by either hGH and/or TPA. Our results indicate that the overall phosphoinositide turnover is slow or confined to small fractions only. On the other hand, the phosphorylation-dephosphorylation cycle of polyphosphoinositides is quite fast and remarkably exceeds the rate of incorporation of [3H]myo-inositol. Our present results indicate, therefore, that the mitogenic effect of hGH and its enhancement by TPA is not mediated by an immediate increase in phosphoinositide metabolism.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D013006:Growth Hormone / Q000494:pharmacology*; D006801:Humans; D007294:Inositol / Q000378:metabolism; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001095:Arachidonic Acids; D010716:Phosphatidylinositols; D016718:Arachidonic Acid; D007294:Inositol; D013006:Growth Hormone; D013755:Tetradecanoylphorbol Acetate