Molecular Human Reproduction, Vol. 6, No. 4, 352-360,
April 2000
© 2000 European Society of Human Reproduction and Embryology
Pregnancy |
Pregnancy is associated with altered response to neuropeptide Y in uterine artery
1 Tayside Institute of Child Health, University of Dundee, Ninewells Hospital & Medical School, Dundee, DD1 9SY, Scotland, UK and 2 Department of Clinical Pharmacology, Pharmacology and Toxicology, Medical School, Belgrade, Yugoslavia
Abstract
Pregnancy is associated with a significant increase in uterine blood flow which contributes to optimal fetal development. Although neuropeptide Y (NPY) is considered to be an important regulator of uterine blood flow, it is not known whether: (i) products from the vascular endothelium modulate NPY action in the uterine artery; (ii) pregnancy changes the responsiveness of the uterine artery to NPY, or (iii) NPY interacts with noradrenaline and acetylcholine on the uterine artery, with pregnancy regulating this possible interaction. In the present study, NPY induced a concentration-dependent contraction of guinea pig uterine arterial rings both intact and denuded of endothelium. Pregnancy significantly decreased the potency of NPY to contract uterine artery with and without endothelium. In all preparations, addition of NG-monomethyl-l-arginine acetate (l-NMMA), indomethacin and diethylcarbamazine did not modify the effect of NPY. In the presence of NPY concentrationresponse curves for acetylcholine and noradrenaline were significantly shifted to the right and left respectively. This effect of NPY was independent of endothelial condition or pregnancy status. The receptor reserve (KA/EC50) for acetylcholine was decreased and for noradrenaline was increased in the presence of NPY, although no changes in the dissociation constants of the neurotransmitterreceptor complexes were observed. Thus, this study has shown that: (i) NPY induces contraction of guinea pig uterine arteries acting on receptors localized in smooth muscle; (ii) pregnancy alters the response of guinea pig uterine arteries to NPY in such a way as to promote vasorelaxation, and (iii) NPY modulates the effect of neurotransmitters on guinea pig uterine arteries, but pregnancy is not associated with the changes at the level of NPYneurotransmitter interaction.
endothelium/neuropeptide Y/pregnancy/uterine artery
Notes