Control of inositol phosphate turnover in human airways during histamine stimulation.
The control of inositol phosphate (IP) turnover was investigated in intact human airway smooth muscle cells (SMC) during a brief exposure to a bronchoconstrictor agonist. The pool of membrane phosphatidylinositol 4,5-biphosphate was labelled by incubating SMC with myo-[3H]inositol and the [3H]IPs synthetized ([3H]1,4-IP2, [3H]1,3,4,-IP3, [3H]1,4,5,-IP3 and [3H]1,3,4,5-IP4) were separated by HPLC. We examined the role of protein kinase C (PKC) and of Ca2+ on IP turnover during a 5 sec application of histamine. Activation of PKC with the phorbol ester PMA (0.2 microM) decreased, whereas inhibition of PKC with 1 microM staurosporine increased the production of the 4 IPs examined in unstimulated and in histamine-stimulated SMC. Decreasing [Ca2+]i with 5 microM ionomycin in the absence of external Ca2+ diminished the IP production whereas in the presence of Ca2+, ionomycin exalted it and potentiated the response to histamine. Thapsigargin, 5 microM, which depletes the 1,4,5-IP3-sensitive Ca2+ stores, reduced the IP production due to histamine. The effects of PMA, staurosporine and thapsigargin were also tested on [Ca2+]i in fura-2-loaded single SMC. These results reveal that PKC exerts a negative and Ca2+ a positive feedback control on phospholipase C, that operate within 5 sec of agonist stimulation.
Marmy
N
N
Institut de Physiologie, Fribourg, Switzerland.
Durand
J
J
D000470:Alkaloids / Q000494:pharmacology; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology*; D006636:Histamine Release / Q000187:drug effects; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012137:Respiratory System / Q000187:drug effects / Q000378:metabolism*; D019311:Staurosporine; D013268:Stimulation, Chemical; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin
D000470:Alkaloids; D007295:Inositol Phosphates; D013729:Terpenes; D019284:Thapsigargin; D006632:Histamine; D004247:DNA; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate