General paper
Seasonal variations in the responses of luteal and follicular luteinizing hormone-stimulated adenylyl cyclases to estradiol implants and implant removal in pseudopregnant rabbits☆

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Abstract

  • 1.

    1. Summer rabbits appeared to be less sensitive to the presence of exogenous estradiol or to the withdrawal of exogenous estradiol than were Winter rabbits.

  • 2.

    2. Suppression of the luteinizing hormone(LH)-stimulated adenylyl cyclase of corpora lutea by estradiol-filled silastic capsules, which resulted in serum estradiol concentrations approximately 3.8 × control (high level), appeared to be greater in Winter rabbits than in Summer rabbits.

  • 3.

    3. Both high level and low level (2.1 × control) estradiol implants suppressed follicular LH-stimulated adenylyl cyclase in Winter rabbits but neither size capsule had an effect in Summer rabbits.

  • 4.

    4. Serum LH concentrations were equally low in Winter rabbits using either high or low level estradiol implants, while only the high level implants caused a decrease in serum LH in Summer rabbits.

  • 5.

    5. Withdrawal of the exogenous estradiol caused a precipitous fall in serum progesterone concentrations in Winter rabbits; estradiol withdrawal in Summer rabbits was without effect.

References (23)

  • M.H Friedman

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    Endocrinology

    (1938)

    • Cited by (0)

    ☆

    This work was supported by NIH grant HD-09581 and was presented in part at the 12th Annual Meeting of the Society for the Study of Reproduction, August 1979, Quebec City, Quebec, Canada.

    †

    Recipient of NIH postdoctoral fellowship HD-05823.

    ‡

    Recipient of NIH postdoctoral fellowship HD-05757. Current address: Department of Zoology, Iowa State University, Ames, IA 50011, U.S.A. To whom all correspondence should be addressed.

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