Endocrine Abstracts

Background

Leptin is suggested to be a permissive factor for puberty by stimulating the secretion of gonadotrophin-releasing hormone by the hypothalamic neurons, and luteinising and follicle-stimulating hormones by pituitary cells.

Objective

To document the ultrastructural changes that occur in the ovarian follicles of immature albino rats treated with leptin when compared with controls.

Subjects and methods

Fifty immature female albino rats aged 22 days (the age of weaning) were divided into Treatment Group that included 24 rats injected with 5 μg leptin daily for 20 days, and Control Group that included 26 rats injected with 5 μg of the solvent daily for the same period. Three animals were sacrificed every 2–4 days from each group, ovaries were dissected and specimens were prepared for electron microscopic (EM) examination. The first author is licensed by the home office to deal with laboratory animals.

Results

The EM examination confirmed the occurrence of ovulation at age of 30 days in the treatment group, while the control rats ovulated at the normal age of maturation which is 40–44 days of age. Leptin-accelerated maturational changes were observed in all ovarian components. The granulose, theca and stroma cells showed signs of steroidogenesis, such as vesicular nuclei, increased cytoplasmic organelles and lipid droplets of variable electron densities. There was high number of granulose cells with mitotic figures. The ooplasm showed an increased number of mitochondria, rough endoplasmic reticulum and cortical granules. Moreover, the annulate lamellae, which appear in rapidly dividing cells, were revealed. The maturation of the zona pellucida was illustrated by microvilli projecting into its substance from the oolemma more than from corona radiata cells, and formation of adhering junctions and gap junctions with the oolemma. Electron photomicrographs of these changes were captured and saved on the computer.

Conclusion

Leptin administration enhanced folliculogenesis and early maturation of all ovarian ultrastructural components of rats. The potential role of leptin, in cases of impaired reproductive functions in human, needs to be elucidated in further experimental and clinical studies.