In order to clarify the mechanism of the failure of reproductive function in diabetic rats, the hypotalamic pitutary-ovarian function in streptozotocin-induced diabetic mature female rats was investigated.
Estrous cycle patterns were disturbed in diabetic rats and these rats showed constant diestrus.
In diabetic rats no preovulatory LH and FSH-surge were observed on presumed proestrus, and the number of ovulated ova and the weights of ovary and uterus were significantly less than those seen in control rats on presumed estrus.
The responses of the pituitary gland to LH-RH in diabetic rats and diabetic castrated rats were not significantly different from those in control rats on diestrous day and castrated control rats, respectively.
However, the response of hypothalamic-pituitary axis to steroidal feedback in diabetic castrated rats were significantly less than those in castrated control rats.
The number of ovulated ova and ovarian growth induced by hCG in diabetic rats were also significantly lower than those in control rats.
These results indicate that the impaired site in streptozotocin diabetic rats is not pituitary gland, but ovary and hypothalamic-pituitary function.
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