Activation of phospholipase A2 and phospholipase C by endothelin-1 in human endometrium.
Human endometrium contains specific binding sites for iodinated endothelin (ET)-1, ET-2 and ET-3, and ET-1 stimulates prostaglandin (PG) F2 alpha synthesis from explants of proliferative endometrium in short-term culture. This study has investigated the cellular responses of normal proliferative endometrium to ET-1. Radioimmunoassay was used to measure PG release and Dowex anion-exchange column chromatography was utilized to assess the accumulation of inositol phosphates. Endothelin-1 induced a significant increase in PGF2 alpha release (basal median: 1465 pg/mg per 60 min (range: 541-3935 pg/mg per 60 min); ET-1-stimulated: 1813 pg/mg per 60 min (1021-5714 pg/mg per 60 min); P < 0.04 using Wilcoxon signed rank test). The effect of ET-1 was attenuated in the presence of the phospholipase A2 inhibitor quinacrine. Endothelin-1 induced a rapid, transient and concentration-dependent hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), measured by the accumulation of tritiated inositol phosphates. Following a 1-min stimulation with ET-1 (100 nmol/l), [3H]inositol mono-, bis- and trisphosphate fractions increased from median values of 490.0 d.p.m./mg dry wt (range: 348.0-807.0 d.p.m./mg dry wt), 120.0 d.p.m./mg dry wt (93.6-144.1 d.p.m./mg dry wt) and 67.0 d.p.m./mg dry wt (54.2-85.0 d.p.m./mg dry wt) to 939.0 d.p.m./mg dry wt (635.9-1596.0 d.p.m./mg dry wt; P < 0.03), 145.0 d.p.m./mg dry wt (127.0-293.9 d.p.m./mg dry wt; P < 0.05) and 146.0 d.p.m./mg dry wt (77.5-187.0 d.p.m./mg dry wt; P < 0.03) respectively. These results suggest that ET-1 activates the phospholipase A2 and PtdIns(4,5)P2-specific phospholipase C in human proliferative endometrium, resulting in the generation of PGF2 alpha and second messengers respectively which are pivotal to endometrial function.
Ahmed
A
A
Department of Obstetrics and Gynaecology, University of Cambridge, U.K.
Cameron
I T
IT
Ferriani
R A
RA
Smith
S K
SK
D004717:Endometrium / Q000187:drug effects / Q000201:enzymology*; D016232:Endothelins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011453:Prostaglandins / Q000096:biosynthesis; D010738:Type C Phospholipases / Q000378:metabolism*
D016232:Endothelins; D007295:Inositol Phosphates; D011453:Prostaglandins; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases