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Biology of Reproduction, Vol 15, 375-380, Copyright © 1976 by Society for the Study of Reproduction
1 Department of Physiology,
University of Pittsburgh,
School of Medicine,
Pittsburgh, Pennsylvania 15261 At the time of orchidectomy adult and immature rats received a subcutaneous implant consisting of a polydimethylsiloxane capsule containing crystalline testosterone. Implant size (and
testosterone dosage) were adjusted on the basis of body weight and measurements of testosterone
concentrations indicated that comparable serum testosterone concentrations were achieved in both
age groups. The testosterone treatment proved to be adequate to prevent the postcastration
increase in serum LH and FSH concentrations in the immature rats but was totally ineffective in
this regard in the adult animals. The data support the concept that the hypothalamo-hypophyseal
system of the immature rat is more sensitive to inhibition by testosterone (or its metabolites) than
that of the adult and suggest that age related variations in the serum testosterone concentrations
produced by such treatment do not account for this differing sensitivity.
Note:
ACKNOWLEDGMENT
The authors gratefully acknowledge the generous
gifts of LH antiserum from Dr. G. D. Niswender,
purified ovine LH from Dr. L. E. Reichert, Jr., and the
testosterone antiserum from Dr. I. H. Thorneycroft.
The reagents for FSH radioimmunoassay and RP-1
standards for both LH and FSH assays were generously supplied by NIAMDD.
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