Effects of melatonin on histomorphology and on the expression of steroid receptors, VEGF, and PCNA in ovaries of pinealectomized female rats

Abstract

Objective: To evaluate the effect of melatonin both on the ovaries of pinealectomized female rats through histomorphometric analysis and on steroid receptors, proliferating cell nuclear antigen (PCNA), and vascular endothelial growth factor (VEGF) expression.

Design: Experimental study.

Setting: Federal University of São Paulo, Brazil.

Animal(s): Forty female rats.

Intervention(s): Forty rats were divided equally into four groups: GI-vehicle without surgery; GII--surgery without removal of the pineal gland (sham); GIII--pinealectomized with vehicle; and GIV--pinealectomized with melatonin treatment. After treatment for 3 consecutive months, the animals were killed and their ovaries removed for analysis.

Main outcome measure(s): Estrogen and progesterone receptors, histologic and immunohistochemical analysis.

Result(s): The GIII samples presented signals of proliferation on ovarian surface epithelium and interstitial cells as well as high expressions of PCNA and VEGF in those structures compared with GI, GII, and GIV. Also, the levels of progesterone receptor (fmol/g) in ovaries of GIII (250.6 ± 32.4) were significantly lower than in those of GI (429.0 ± 23,8), GII (442.3 ± 30.2), and GIV (564.1 ± 78.7). The levels of progesterone in GIII were superior to those in GI, GII, and GIV.

Conclusion(s): Our findings suggest that melatonin may attenuate proliferation in ovarian structures and increase the number of luteal bodies as well as the levels of progesterone receptor.