Patterns of spontaneous pulsatile secretion of human chorionic gonadotropin and pregnancy specific β1 glycoprotein by superfused placental explants in first and last trimester. Lack of episodic human placental lactogen secretion

We have recently reported that during superfusion of placental explants, human chorionic gonadotropin secretion is episodic. In the present work we have examined, using the superfusion model, the pattern of secretion of other glycoprotein hormones, pregnancy specific β1 glycoprotein and human placental lactogen, in the first trimester and term placenta. This was done by evaluating the pulsatile pattern by two different computerized programmes. By using different sampling intervals (6-0.5 min) of the effluent, two distinct patterns of hCG secretion were detected in the first trimester: a short one, occurring every 8-9 min and the other every 18-25 min. In contrast, at term the only episodic pattern detected was every 40-50 min, with a low amplitude, 20-30% above baseline, and a declining baseline. In two out of seven placentas, no pulsatility was detected. The secretion of pregnancy specific β1 glycoprotein was pulsatile, occuring every 14-15 min in the first trimester and every 6-7 min at term. Finally, the secretion of human placental lactogen at term was not pulsatile. The levels of this glycoprotein in the first trimester placenta were below detection limits. In conclusion, the patterns of the three glycopoproteins during superfusion are different, suggesting different paracrine/autocrine control mechanisms. The dynamic superfusion model also enables identification of thus far not reported gestational age-dependent differences in the secretion pattern of hCG and pregnancy specific β1 glycoprotein.