Ovine placental lactogen stimulates glycogen synthesis in fetal rat hepatocytes.

The effects of placental lactogen on glycogen metabolism have been studied in cultured hepatocytes from 20-day-old fetal rats. Ovine placental lactogen (oPL; 2, 5, 10, and 25 micrograms/ml) stimulated dose-dependent increases in [14C]glucose incorporation into glycogen and total cellular glycogen content after 4 h of incubation but had no effect on glycogen degradation. Half-maximal stimulation occurred with an oPL concentration of 3 micrograms/ml. In contrast, human placental lactogen had no effect on [14C]glucose incorporation into glycogen. Ovine growth hormone (50 and 100 micrograms/ml), rat growth hormone (20, 40, and 100 micrograms/ml), and ovine prolactin (10, 40, and 100 micrograms/ml) stimulated dose-dependent increases in [14C]glucose incorporation into glycogen, but the potencies of these hormones were only 10-20% of that of oPL. Insulin (20 nM) stimulated [14C]glucose incorporation into glycogen, whereas glucagon (0.5 and 20 nM) inhibited [14C]glucose incorporation into glycogen and increased glycogen degradation. Our findings suggest that oPL may have direct insulin-like effects on carbohydrate metabolism in the fetus and that oPL may contribute to the accumulation of fetal liver glycogen that occurs in late gestation.

Duke Scholars

Author Michael Scott Freemark Pediatrics, Endocrinology