RESUMO
OBJECTIVE: To investigate the effects of atrial natriuretic peptide (ANP) on ovarian regulation in mice through intraperitoneal administration. STUDY DESIGN: Forty-two ICR strain female mice were divided into seven groups, including one control. Each mouse received ovarian hyperstimulation. ANP was prepared with saline at concentrations of 0 (as control), 2, 4, 8, 10, 20, and 30 ng/g of body weight. The solution was intraperitoneally applied to each referred group (n = 6) 1 h before the hMG and hCG injections. The mice were sacrificed next morning and blood samples were collected for analysis. RESULTS: A significant reduction in both ovarian weight and the number of oocytes was found as the ANP dosage increased. ANP treatment decreased both serum estradiol and progesterone levels. The pituitary FSH and LH contents elevated significantly by ANP at a dosage larger than 4 ng/g of body weight; however, both serum FSH and LH levels remained unchanged. Histologically, there were remarkable ovarian inhibitory features, i.e. reduction in size and number of follicles, arrest of follicular growth and diminution of ovulation. CONCLUSION: Intraperitoneal administration of ANP inhibits the follicular growth, ovulation and steroidogenesis in female mice. These effects are attributed to the direct action of ANP on ovaries.