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Ontogenesis of Pituitary Prolactin in the Human Fetus^*

The Research Institute of Environmental Medicine Nagoya, Japan
Department of Obstetrics and Gynecology, School of Medicine Nagoya University Nagoya, Japan

Address all correspondence and requests for reprints to: Dr. Nobuhiko Suganuma, Department of Obstetrics and Gynecology, Nagoya University School of Medicine, 65, Tsurumai-cho, Showa-ku, Nagoya 466, Japan.

To study the ontogenesis of PRL synthesis and secretion in the human fetus, PRL mRNA was measured in 12 pituitaries from fetuses of 16–27 weeks of gestation by hybridization of cytosol RNA with ¹²⁵I-labeled single stranded complementary DNA (_cDNA). Pituitary PRL content and serum PRL concentration were assessed by RIA.

Pituitary weight increased with fetal age, ranging from 12 mg at 16 weeks of gestationto 41 mg at 27weeks. The increased weight was due to an increase in cell number. PRL mRNAcontent did not change during weeks 16–20 of gestation. However, it increased rapidly after 21 weeks,reaching 11.5 times the 16–20 week value at 27 weeks. Pituitary PRL content was constant at a low level until 21 weeks, but thereafter it increased markedly. The increase was greater than that in PRL mRNA, and therefore, the PRL to PRL mRNA ratio was 10-fold greaterat27 weeks of gestation. Serum PRL concentrations also gradually increased after 21 weeks of gestation.

These results indicate that marked increases in fetal pituitary PRL synthesis and release occur after 21 weeks of gestation.

^* This work was supported in part by a Grant-in-Aid for Cancer Research from the Ministry of Education, Culture, and Science and the Ministryof Health and Welfare, Japan.

Received October 21, 1985.