الفهرس 
Introduction and Aim of the WorkOnly 14 pages are availabe for public view
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Abstract
Over the last few years, many studies have focused on leptin, the product of the LEP (ob) gene, searching for a possible link between energy balance and reproduction. The aim of our work was to investigate the effect of daily leptin injection on prepubertal female rats.
Our study applied on 32 female albino rats weaned after 21 days. They were divided into two groups 16 rats in each, group I treated with daily I.P leptin injection in a dose of 5μg/g from 22 to 42 days age, group II (control) injected daily with saline. The animals were assessed daily for body weight and VO. Vaginal smears were taken daily from rats showing VO to detect VE. At 28, 32, 38 and 42 days of age 3 rats of each group were anesthetized and dissected 3 hours from the last dose of leptin. Blood collected from the heart for E2
and LH assay. The ovaries were dissected and fixed in Bouin’s solution and stained with H & E for histological examination.
In this work Statistical analysis was performed by SPSS version 17. Data were compared between groups using an Analysis of Variance (ANOVA) for repeated measures. A twotailed P < 0.05 was considered significant in all the statistical tests.
Weighting the animals of the two groups daily, there was a linear increase in body weight with time, but we did not find significant difference between both groups (P=0.26).
There was earlier incidence of VO in the treated group (p<0.001), the mean age for VO was 29.8±1.1 days in the treated group while it was 31.3±0.95 days in the control group.
We detected significant earlier appearance of VE in leptin group (P<0.001).The mean age for VE in leptin group was 30.6±1 days while it was 35.6±2.4days in control group.
Measuring the plasma E2 level at 28,32,38,42 days of age, we found a significant increase in E2 with time in both groups (P-value<0.001), but serum levels of E2 were significantly higher in leptin treated rats (P-value<0.001).
Measurements of LH hormone at 28,32 ,38 and 42 days showed significant increase in LH levels in leptin treated and control groups at 32 days age (P-value was 0.01), but there was no significant difference in LH levels between both groups (P-value was 0.2).
On Histological examination of the ovaries, we found a significant increase in the numbers of primary, growing and mature follicles in the leptin treated groups when compared with the controls with P < 0.03, P< 0.003 and P<0.02 respectively. Ovulation was detected in the treated group as early as 28 days while it wasn’t detected in the control group till 42 days. There was a significant increase in the number of corpora lutea in leptin treated
group (p <0.001).
from this work it can be concluded that daily injection of prepubertal female rats lead to earlier onset of puberty and its manifestation. Leptin acts on the reproductive axis both centrally and peripherally. Leptin could be a possible link between the body fat and timing of puberty together with other factors. We need more studies to reveal the exact mechanisms by which leptin reveals it effect. We need to study the effect of different leptin doses on the onset of puberty.