Abstract
Summary
Stimulation of LH release by administration of natural or synthetic luteinizing hormone-releasing hormone (LH-RH) was studied at different stages of the estrous cycle in the golden hamster. The animals were pretreated with phenobarbital to prevent a spontaneous preovulatory surge of LH. In these animals serum LH levels after saline injection remained low throughout the estrous cycle. Intravenous injection of 0.1 or 0.4 μg LH-RH significantly increased serum LH levels compared to appropriate controls. The greatest response to LH-RH was observed during proestrus. The smallest response was observed on the day 1 of diestrus, and in most of the animals, at estrus. The pituitary response to LH-RH on day 2 of diestrus was smaller than during proestrus, and greater than that observed during day 1 of diestrus and estrus. The results indicate that pituitary responsiveness to LH-RH varies at different stages of estrus cycle in the golden hamster.
The authors are indebted to Drs. G. D. Niswender and H. Papkoff and to NIH, Endocrinology Study Section for the gift of antiserum and ovine LH for iodination and standard preparation respectively. The technical help of Mrs. N. Machen, Mrs. J. Gauthier and Mrs. M. Esslinger and the editorial advice of Dr. E. B. Ferguson, Jr., are also gratefully acknowledged.
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