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Immunoreactive and bioactive LH release from pituitaries of intact or castrated male rats: Effect of in vitro GnRH and KCl administration

Journal of Endocrinological Investigation volume 20, pages 381–386 (1997)Cite this article

Abstract

The in vitro immunoreactive (i-LH) and bioactive (b-LH) LH release from hemipituitaries of intact adult male rats (INT) or rats castrated 7 days earlier (CAS) was studied. Hemipituitaries were incubated for 30 min (time 1) plus an additional 30 min (time 2) with GnRH (10 nM) and/or KCl (50 mM), according to one of the following protocols: media alone (C), KCl+KCl (K/K), GnRH+GnRH (G/G), KCl+GnRH (K/G), GnRH+KCl (G/K). All of the hemipituitaries were further incubated in media alone for 120 min (time 3). I-LH, b-LH and i-FSH were assayed on the media. In both models, the highest bioactive:immunoactive (b/i) ratio was noted during time 1; however, CAS always secreted more b-LH than INT at any given time of the study. In INT, GnRH — but not KCl — administration during time 2 resulted in blunted i-LH. During the same time, the b/i ratios decreased in all groups but G/K. LH secretion recovered during time 3 in all groups. In CAS, i-LH levels comparable to those of time 1 were sustained by either stimulus during time 2, while the b/i ratios were markedly decreased. LH secretion recovered in the K/K group during time 3. These results suggest that: 1) promptly releasable pools of b-LH are available in both models; 2) CAS always secrete more b-LH; 3) in INT, desensitization occurs involving parallel changes in both i-LH and b-LH, while changes in b-LH rather than i-LH are noted in CAS; 4) prolonged KCl administration might play a role in new gonadotropin synthesis and/or release.

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Affiliations

  1. DISEM, University School of Medicine, Viale Benedetto XV, 6, 16132, Genova, Italy

    Sandra Valenti M.D., M. Giusti & G. Giordano

  2. Veterans Affair Medical Center, 1660 South Columbian Way, Seattle, WA, USA

    A. Sarkissian & K. D. Dahl

Authors
  1. Sandra Valenti M.D.
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  2. A. Sarkissian
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  3. M. Giusti
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  4. G. Giordano
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  5. K. D. Dahl
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Valenti, S., Sarkissian, A., Giusti, M. et al. Immunoreactive and bioactive LH release from pituitaries of intact or castrated male rats: Effect of in vitro GnRH and KCl administration. J Endocrinol Invest 20, 381–386 (1997). https://doi.org/10.1007/BF03347988

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  • DOI: https://doi.org/10.1007/BF03347988

Key-words

  • LH
  • pituitary
  • bioactivity
  • GnRH
  • KCl