Endocrine Abstracts

Background

Leptin serves as a signal to the central nervous system with information on the critical amount of adipose tissue stores that is necessary for activation of the hypothalamic-pituitary-ovarian axis.

Objectives

To determine the endometrial histological changes and vaginal cytological alterations, suggestive of ovulation and the onset of the oestrus phase of the oestrus cycle, that occur in the immature albino rats treated with leptin when compared with controls.

Subjects and methods

Fifty immature albino rats aged 22 days (the age of weaning) were divided into Treatment Group that included 24 rats injected daily with 5 μg leptin for 20 days, and Control Group that included 26 rats injected daily with 5 μg of the solvent for the same period. Vaginal smears were taken daily from all animals and stained with Giemsa stain. Three animals were sacrificed every 2–4 days from each group, uteri were dissected and specimens were prepared for haematoxylen and eosin (H&E) and immunohistochemical staining for oestrogen receptor α (ERα). Increased expression of ERα is an indication for the onset of the oestrus cycle. The first author is licensed by the home office to deal with laboratory animals.

Results

The endometrial and vaginal maturational changes were detected in leptin-treated rats from 26 days of age. Nonetheless, they were not revealed in the control rats till 40–44 days of age. The endometrial lining was formed of partially ciliated columnar cells with infoldings of the endometrium to form elongated gland-like tubular structures. The lining cells were over-crowded giving a pseudostratified appearance. Further, there was high expression of ERα in almost all columnar and stroma cells. The smears were less sticky with reduced fibrin-like filamentous component and leucocytes. Many large desquamated nucleated epithelial cells were detected. Images of these changes were captured and saved on the computer.

Conclusion

Leptin administration induced changes in the endometrium and vagina suggestive of premature ovulation and the onset of oestrus phase of the cycle. Further studies are required to evaluate the possible clinical implications of leptin in human.