Pre-b-HDL stimulates placental lactogen release from human trophoblast cells

Handwerger, Stuart, Geeta Datta, Brian Richardson, Carrie M. Schmidt, Tariq Siddiqi, Lisa Turzai, and G. M. Anantharamaiah. Pre-b-HDL stimulates placental lactogen release from human trophoblast cells. Am. J. Physiol. 276 (Endocrinol. Metab. 39): E384–E389, 1999.—To examine whether pre-b-high-density lipoprotein (HDL) may be involved in regulation of human placental lactogen (hPL) release, pre-b-HDL was isolated from term pregnancy serum, and the effect of purified pre-b-HDL on hPL release from trophoblast cells was examined after 1 h of exposure. Pre-bHDL stimulated a dose-dependent increase in hPL release with half-maximal stimulation at a dose of 300–400 μg/ml, which is within the normal physiological range during pregnancy. Analysis of pre-b-HDL and a-HDL in serum from pregnant women at different stages of gestation (determined by Western blot analysis) indicated that the pre-b-HDL-to-aHDL ratio increased linearly after the 10th week of gestation (r 5 0.88, P , 0.001), reaching a maximum sixfold greater than that of nonpregnant women. The increase in serum pre-b-HDL during pregnancy paralleled that of plasma hPL concentrations (r 5 0.93, P , 0.001). Two-dimensional electrophoresis indicated that the increase in pre-b-HDL was due primarily to an increase in pre-b1-HDL and pre-b2-HDL, two of the three forms of pre-b-HDL present in blood. These results suggest a role for pre-b-HDL in the regulation of hPL expression during pregnancy.