Dopamine and morphine stimulate nitric oxide release in human endometrial glandular epithelial cells

OBJECTIVE: Previous studies have shown that human endometrial glandular epithelial cells contain endothelial nitric oxide synthase indicating that the endometrium might produce nitric oxide (NO). We conducted this study to identify stimuli that can activate a transient NO release from endometrial glandular epithelial cells because NO is an important intracellular and intercellular signal transduction pathway in reproductive cycle. METHODS: Endometrial glandular epithelial cells, free of endothelial cells, were isolated from human endometrial specimens and maintained viable in RPMI 1640 medium with 2% fetal bovine serum for 2-4 days. Nitric oxide release from the glandular cells in response to stimuli was monitored continuously amperometrically. RESULTS: Among the substances examined, we found that dopamine and morphine stimulated a transient surge of NO production that was dose-dependent, whereas estrogen, progesterone, or relaxin (RLX) had no short-term effect on NO release. Cells treated with RLX or dopamine for 4 days enhanced the dopamine-induced NO release fourfold to sixfold, with the peak of the NO surge shifting from 35 to 15 seconds. CONCLUSION: Endometrial glandular cells were capable of producing NO. Dopamine and morphine were potent stimuli for a transient surge of NO release from endometrial glandular cells. Furthermore, prolonged exposure to dopamine or RLX enhanced the sensitivity of NO release in endometrial glands.