ABSTRACT
Leptin is an adipocyte secreted hormone with a well documented metabolic role causing body weight loss. Leptin hormone has been further implicated in fertility regulation and it appeared to be a permissive factor for puberty. The present study focused on the assessment of the histological changes that might occur in the ovaries of immature female albino rats in response to the repeated injections of leptin hormone. Fifty seven just-weaned, immature female albino rats [22days old] were divided among control groups that had received daily subcutaneous injections of HC1/NaOH solvent; and experimented groups that had received daily 5pg of subcutaneous leptin hormone till the age of 44days [total experimental duration was 22 days]. The body weights of rats were daily recorded. The females were subjected to daily vaginal smears stained by Giemsa stain for assessment of the onset of the oestrus cycle. Three animals from both groups were sacrificed by decapitation every two days after the injections until reaching the expected age of maturation in female albino rats [42-44 days old]. The weights of the dissected ovaries were recorded. Sections from the ovaries and uterus were examined histologically by routine hematoxylin and eosin [H and E], trichrome and periodic acid Schiff's stains PAS]. Counting of the large growing antral follicles in all ovarian H and E sections was done, statistically analysed and represented. The endometrium in selected groups was labelled for the immunohistochemical detection of the expression of the nuclear alpha oestrogen receptor. The ovaries were also examined by the transmission electron microscope for the assessment of the maturation changes at the cellular level within the different structural components of the ovaries. Revealed that, in addition to the reduction in the total body weight, leptin hormone accelerated the maturation of the ovarian follicles and stromal tissue in immature female rats as early as the age of 26 days with enhancement of the early onset of the oestrus cycle and the associated changes in these females. These results were highly significant compared to the equivalent control female rats, which started to show ovarian maturation changes only on approaching the age of 42-44 days. It was suggested that leptin hormonal therapy could be beneficial for the management of delayed puberty in young females and maybe in related reproduction disorders particularly f associated with overweight problems