Acute effects of cadmium on preovulatory serum FSH, LH, and prolactin levels and on ovulation and ovarian hormone secretion in estrous rats

Abstract

On the day of diestrus II CFY rats were given 5, 10, or 15 mg/kg cadmium chloride (CdCl 2) or 1.0 mL/kg of 0.9% NaCl. On the next day a group of animals was anesthetized with pentobarbital and blood was collected from the aorta at 13:00, 15:00, 16:30, or 18:00 h. for FSH, LH, prolactin (PRL), progesterone (P), and estradiol-17β (E 2) determination. On the day of the expected estrus, the second group of animals was anesthetized with pentobarbital and cannulas were inserted in one of the femoral arteries and veins, and in one of the utero-ovarian veins. Five-minute blood fractions were collected from the ovary for 40 min, and following the first blood samples, 10 IU hCG was injected iv. Ovarian venous outflow and blood pressure were continuously recorded. From the blood fractions, P and E 2 were determined, and their secretion rates were calculated. In a third group of treated animals, the ovaries were excised for histological examination, and oviducts were flushed for counting oocytes. CdCl 2 in the dose of 10 or 15 mg/kg increased the PRL serum levels at 13:00 h; it diminished FSH serum levels in the dose of 10 mg/kg and LH serum levels in the doses of 10 and 15 mg/kg at 15:00 h. The decrease in LH levels continued until 16:30 h in the dose of 10 mg/kg CdCl 2. In estrous animals, CdCl 2 did not influence the blood pressure and ovarian blood flow. In animals receiving 10 or 15 mg/kg CdCl 2, a decrease in basal secretion of P occurred. The hCG induced a rapid rise in P secretion of controls; the 5 mg/kg CdCl 2 diminished the effect of hCG, and the 10 and 15 mg/kg completely abolished it, but failed to influence the basal secretion of E 2 and its response to hCG. CdCl 2 prevented ovulation in 40% to 50% of the animals; however, when ovulation occurred, normal oocyte numbers were found. No alteration could be observed in the light microscopic histology of ovary.