Presence of Acetylated and Shortened Endorphins in Human Fetal Pituitary Gland

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Abstract
A total of 21 human fetal pituitaries was collected from spontaneous abortions (11 cases) or prostaglandin (PG)-induced abortions at the second trimester. Pituitaries were homogenized, fractionated by HPLC, and the fractions were tested by specific RIA for α-endorphin (EP) (ß-EP 1-16), 7-EP γ-EP 1-17), ß-EP (ß-EP 1-31), and their α-N-acetylated derivatives. In the fetal pituitaries collected after spontaneous abortion, the contents of α-EP (23.4 ± 7.5 pmol/mg prot, mean ± SE) and γ-EP (28.9 ± 9.7) were similar to those of ß-EP (28.6 ± 7.4). Both ß-EP/α-EP (1.2 ± 0.3) and ß-EP/γ-EP (1.1 ± 0.3) ratios approached unity. Although 35.7 and 30.2% of α-EP and γ-EP were acetylated, acetyl-ß-EP was only 8.4% of the total ß-EP immnoreactivity. In the five cases of PG-induced abortion that were more than 20 wk of pregnancy, the pituitary content of ß-EP (75.9 ± 21.2) and γ-EP (26.2 ± 7.5) were significantly higher than in samples collected after spontaneous abortion (13.3 ± 8.2 and 5.9 ± 1.8, respectively, p1) ß-EP retains its opioid biologic activity because only a small percentage is acetylated, 2) shortened endorphins are quantitatively as important as ß-EP, and 3) after mid-gestation, the fetal proopiomelanocortin synthesis or processing may be sensitive to endocrine or environmental stimuli.

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