The potential role of periovarian fat and leptin in initiation of puberty in the immature rat.

Twenty-four-day old female rats were injected with 25 microg recombinant leptin twice daily for 24, 48, 72, or 93 h. Periovarian fat contained significantly greater amounts of aromatase mRNA at 72 and 93 h and estradiol at 72 h after leptin treatment as compared to the ovary. On the other hand, there was an increase in testosterone at 72 h and progesterone at 72 and 93 h after leptin in the ovary as compared to periovarian fat. Cholesterol side chain cleavage and 17alpha-hydroxylase mRNA were found only in the ovary and not periovarian fat. Thus, periovarian fat has a greater capacity to synthesize estrogen than the ovary in the immature rat and adipose tissue may serve as the primary source of estrogen in the prepubertal period which results in the onset of puberty.