Opposite effects of an antilipolytic hormone (nicotinic acid) on the production/secretion of hCG and hPL by isolated trophoblast cells

Summary Human trophoblast cells were isolated from term placenta and cultivated for 8 days. The released amounts of alpha-hCG, hCG, and hPL were measured in culture media which were changed every 24 hours. Addition of nicotinic acidd, an antilipolytic hormone, to the culture media resulted in a dose-dependent increase of alpha-hCG and hCG and decrease of hPL release, if the amounts of secreted hormones were accumulated over 8 days. The temporal changes of hormone secretion by nicotinic acid stimulated cells essentially resembled those of control cells which showed the well known pattern. Alpha-hCG, hCG, and hPL levels were peaking at days 3, 4, and 5, respectively. Thereafter the values gradually declined to day 8. Significant stimulatory or inhibitory effects of nicotinic acid were only observed between days 4 and 6 in culture. Cycloheximide inhibited the secretion of hormones after 48 or 72 hours in both control and nicotinic acid treated cells, indicating that the nicotinic acid induced hCG increase was caused by stimulated hormone synthesis. Simultaneous incubation of nicotinic acid with a protein kinase C inhibitor blocked the effects of nicotinic acid, leading to amounts of released hPL as in untreated control incubation and to hCG levels which were reduced to as low as 30% of control. The results suggest that nicotinic acid is able to modify hCG and hPL release from human trophoblast cells in vitro.