title: Effect of melatonin on estrogen and progesterone receptors in relation to uterine contraction in rats.
abstract: The present study was designed to investigate the possible modulator effect of melatonin on uterine estrogen and progesterone receptors in rats as well as the uterine response to oxytocin. Non-pregnant rats were pretreated with melatonin in a dose of 0.8 mg kg(-1) per day for 15 consecutive days. Control animals received the vehicle. The uterus was dissected out and uterine contraction in one horne was recorded in vitro for each animal as a response to oxytocin (0.5 x 10(-11) to 2 x 10(-11)M). The other uterine horne was subjected to estrogen and progesterone receptors detection by immunohistochemical and image analysis techniques. The results reveal a significant reduction (59%) in the number of uterine estrogen receptors with concomitant increase in the progesterone receptors (53%) in melatonin-pretreated rats as compared to the control ones. In addition, our data show an inhibitory effect of melatonin on the uterine contraction as a response to oxytocin (0.5 x 10(-11), 1 x 10(-11), and 2 x 10(-11)M) amounting to 48, 77, and 59.5% reduction, respectively, in the amplitude of contraction as well as 62, 19.9, and 47% reduction in the area under the curve (AUC) of uterine contractions, respectively. The data, so far obtained, may indicate a possible relationship of melatonin-induced modulation of the number of estrogen and progesterone receptors and its inhibitory effect on uterine contraction. These findings merit further investigations on the possible beneficial role of melatonin in a plethora of hormone-dependent uterine disorders.
authors.affiliation: Department of Pharmacology and Toxicology, Faculty of Pharmacy, Al-Azhar University, Cairo, Egypt. arabdallah@hotmail.com
authors.forename: Adel R A
authors.initials: AR
authors.lastname: Abd-Allah
authors.forename: El Sayed M
authors.initials: el SM
authors.lastname: El-Sayed
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Abdel-Wahab
authors.forename: Farid M A
authors.initials: FM
authors.lastname: Hamada
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D005260:Female; D008550:Melatonin / Q000494:pharmacology*; D010121:Oxytocin / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011960:Receptors, Estrogen / Q000187:drug effects*; D011980:Receptors, Progesterone / Q000187:drug effects*; D014590:Uterine Contraction / Q000187:drug effects* / Q000502:physiology
chemical_list: D000975:Antioxidants; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D010121:Oxytocin; D008550:Melatonin