Abstract
Abstract
Immature female rats were injected with streptozotocin (60 mg/kg, iv) 3 to 4 days prior to the injection (iv) of 20 IU of pregnant mare's serum gonadotropin (PMS). Animals were killed at various intervals and the serum levels of estradiol, luteinizing hormone (LH), and progesterone were determined by radioimmunoassays. The ovarian steroid 17α-hydroxylase activity was determined by a tritium exchange assay using pregnenolone as the substrate. Ovulation was determined 72 hr after PMS by flushing of the oviducts. The diabetes mellitus induced by the drug reduced the number of animals ovulating and in some animals the number of ova shed when compared to controls. However, a surge in LH, which reached a peak at 60 hr, was seen in the diabetic animals; a larger peak with the same timing was found in the controls. Changes in ovarian 17α-hydroxylase also indicated that an increase in LH release occurred in the diabetic animals at about 60 hr. Estradiol levels were higher, but progesterone levels lower, in diabetic than control animals. Administration of 1 mg of progesterone to diabetic animals 48 hr after PMS resulted in an increase in the number of animals ovulating and the number of ova shed. The results indicate that hyperglycemia induced by streptozotocin is not inconsistent with production of an LH surge or with ovulation following ovarian stimulation by PMS. However, the lowered production of progesterone, which may be a cause or a result of lowered LH output, appears to be a primary factor in the reduced ovulatory rate.
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