Inhibition of oxytocin-stimulated phosphoinositide turnover in rat myometrium by pertussis and cholera toxins may involve protein kinase A activation.
Both pertussis and cholera toxins inhibit oxytocin-stimulated phosphoinositide turnover in rat myometrium. The actions of pertussis and cholera toxins as well as those of CPTcAMP are reversed by H-8, an inhibitor of protein kinase A. H-8 does not have a major effect on cAMP elevation by the toxins in the presence of oxytocin. The results suggest that the stimulation by oxytocin of phosphoinositide turnover does not involve direct obligatory coupling to a pertussis toxin-sensitive GTP-binding protein. Rather, indirect effects on protein kinase A activation may contribute to the inhibitory effects of both cholera and pertussis toxins. This study suggests that caution must be exercised in interpreting inhibition of phosphoinositide turnover by pertussis toxin in whole cell experiments as indicative of direct involvement of a toxin-sensitive GTP-binding protein.
Singh
S P
SP
Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77030.
Anwer
K
K
Wen
Y
Y
Sanborn
B M
BM
D000818:Animals; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000494:pharmacology; D037342:Pertussis Toxin; D010716:Phosphatidylinositols / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007546:Isoquinolines; D010716:Phosphatidylinositols; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D010121:Oxytocin; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D002772:Cholera Toxin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011494:Protein Kinases; D011493:Protein Kinase C; D019204:GTP-Binding Proteins