Abstract
Summary
Long–term ovariectomized rats primed with estrogen and progesterone responded to exogenous LHRH at dosages of 40 and 100 ng with a sharp rise in plasma LH, peaking at 10–20 min after injection and gradually returning to control levels. In contrast, intact rats treated a week earlier with PMS followed by hCG completely failed to respond to even the higher dosage of LHRH: plasma LH levels remained almost undetecable in these animals. Assays of pituitary extracts revealed a similar concentration and content of prolactin but very depressed values for pituitary LH in these PMS–hCG–treated rats compared with earlier studies in OVX–E2–P animals.
We thank Dr. A. V. Schally for supplying the synthetic LHRH and Dr. A. F. Parlow and the NIAMDD Hormone Distribution Program for making the RIA kits available. Ms. Frances Smith, Virginia Hoover, and Katherine Bangs and Mr. David Whitmoyer supplied valuable technical assistance.
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