Influence of estrogen replacement and aging on the expression of nerve growth factor in the urethra of female rats

Abstract

To evaluate the expression of nerve growth factor (NGF) in the urethra of adult female rats in different hormonal status using immunohistochemical assay. Forty-eight rats (Rattus norvegicus albinus, Rodentia, Mammalia) from the CEDEME-UNIFESP laboratory animal facility were used in the study. Rats were divided into four groups: group A, 12 non-neutered rats; group B, 12 oophorectomized rats; group C, 12 castrated rats treated with 17β-estradiol for 30 days; and group D, 12 aging rats. Animals were killed by lethal injection and their urethra was removed. NGF expression was evaluated by means of immunohistochemistry using mouse monoclonal primary IgG antibody anti-NGF diluted 1:600, and read under 400× magnification. Digital analysis of the images was done by Imagelab software. The intensity of the dark brown color was used as a measure of NGF cytoplasmatic expression, and was used to quantify the percentage of epithelial and muscular layer cells showing this neurotrophin. After oophorectomy, rats showed a significant increase in NGF expression in the periurethral muscular layer. Compared with oophorectomized rats, NGF expression increased in the epithelial layer and diminished in the periurethral smooth muscle following estrogen administration. In 18-month-old rats, NGF expression was diminished in both epithelial and muscular layers. Hormonal status led to significant differences in NGF protein expression in urethral epithelium and periurethral smooth muscle.