Pregnancy enhances G protein activation and nitric oxide release from uterine arteries.
We hypothesized that pregnancy modulates receptor-mediated responses of the uterine artery (UA) by altering G protein activation or coupling. Relaxation and contraction to NaF (0.5-11.5 mM), acetylcholine (10(-9)-10(-5) M), and bradykinin (10(-12)-3 x 10(-5) M) were measured in isolated UA of pregnant and nonpregnant guinea pigs. Responses were measured in the presence and absence of either cholera toxin (2 microg/ml) or pertussis toxin (Galpha(s) and Galpha(i) inhibitors, respectively). NaF relaxation was endothelium dependent and nitro-L-arginine sensitive (a nitric oxide synthase inhibitor). Relaxation to NaF, acetylcholine, and bradykinin were potentiated by pregnancy. Cholera but not pertussis toxin increased relaxation to acetylcholine and bradykinin in UA from nonpregnant animals, had no effect in UA from pregnant animals, and abolished the pregnancy-induced differences in acetylcholine relaxation. Cholera toxin potentiated the bradykinin-induced contraction of UA of both pregnant and nonpregnant animals, whereas pertussis toxin inhibited contraction of UA from pregnant animals only. Therefore, pregnancy may enhance agonist-stimulated endothelium-dependent relaxation and bradykinin-induced contraction of UA by inhibiting GTPase activity or enhancing Galpha(s) but not Galpha(i) activation in pregnant animals. Thus the diverse effects of pregnancy on UA responsiveness may result from hormonal modulation of G proteins coupled to their specific receptors.
Thompson
L P
LP
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Weiner
C P
CP
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology; D002772:Cholera Toxin / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006168:Guinea Pigs; D008469:Meclofenamic Acid / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D037342:Pertussis Toxin; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D012969:Sodium Fluoride / Q000494:pharmacology; D014599:Uterus / Q000098:blood supply*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D010566:Virulence Factors, Bordetella; D019335:Nitroarginine; D009569:Nitric Oxide; D008469:Meclofenamic Acid; D012969:Sodium Fluoride; D002772:Cholera Toxin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000109:Acetylcholine; D001920:Bradykinin