Mechanism of phorbol ester inhibition of histamine-induced IP3 formation in cultured airway smooth muscle.
Cytosolic calcium is a key determinant of the contractile state of airway smooth muscle (ASM). To investigate the mechanisms by which histamine affects cytosolic calcium, we measured changes in inositol 1,4,5-trisphosphate (IP3) following the addition of histamine to cultured canine ASM cells. The effect of phorbol 12-myristate 13-acetate (PMA) on IP3 formation was investigated under conditions previously shown to abolish histamine-induced calcium release. In both intact cells and ASM membranes, histamine produced a significant increase in IP3 formation, which was inhibited by PMA. The site of this blockade was investigated by examining the effect of PMA on guanine nucleotide-stimulated IP3 formation and on phosphoinositide-specific phospholipase C (PI-PLC) activity in ASM membranes. Guanine nucleotide-stimulated IP3 formation was inhibited by PMA pretreatment. Membrane-associated PI-PLC activity was also decreased, an effect that was not due simply to a shift in the calcium sensitivity of the enzyme. We conclude that in cultured canine ASM cells, PMA blocks histamine-induced IP3 formation and that this inhibition is caused, in part, by a postreceptor site of action of protein kinase C, possibly via a direct effect on PI-PLC.
Murray
R K
RK
Department of Medicine, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104.
Bennett
C F
CF
Fluharty
S J
SJ
Kotlikoff
M I
MI
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004285:Dogs; D019204:GTP-Binding Proteins / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007700:Kinetics; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects / Q000502:physiology*; D010738:Type C Phospholipases / Q000378:metabolism
D006632:Histamine; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate