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Inhibition of Decidual Prolactin Release by a Decidual Peptide^*

Department of Pediatrics, Duke University Medical Center Durham, North Carolina 27710

Address all correspondence and requests for reprints to: Stuart Handwerger, M.D., Duke University Medical Center, Box 3080, Durham, North Carolina 27710.

Conditioned media from cultures of human decidual explants and aqueous extracts of human decidual tissue contain a factor that causes a reversible dose-dependent inhibition of decidual PRL release in vitro. Decidual explants incubated for 30 min in medium containing 50, 100, and 250 µg/ml of a dialyzed and lyophilized preparation of decidual conditioned medium (DCM) released 32.4 ± 2.7%, 70.9 ± 4.5%, and 100.0%, respectively, less PRL than control explants. DCM, however, had no measurable effect on the synthesis of decidual PRL or the synthesis and release of trichloroacetic acid-precipitable ³⁵S-labeled proteins. The effect was of short duration and completely reversible. The inhibition of decidual PRL release was not due to PRL, since 500 µg/ml human pituitary PRL (a PRL concentration 40 times that in the minimal effective dose of DCM) added to the incubation medium of decidual explants had no effect on the synthesis or release of decidual PRL or trichloroacetic acid-precipitable ³⁵S-labeled decidual proteins. The inhibitory activity eluted from Sephadex G-200 with an apparent molecular weight of 38,000–45,000 daltons, was heat labile, was destroyed by treatment with trypsin, and was unaffected by extraction with acetone-ethanol. These results strongly suggest that the release of decidual PRL is under local control, regulated in part by a factor(s) other than PRL that is released by the decidua.

^* This work was supported by NIH Grants HD-15201 and HD-06153. Presented in part at the 65th Annual Meeting of The Endocrine Society, San Antonio, TX, June 1983.

Received June 7, 1983.