Physiological concentrations of albumin stimulate chorionic gonadotrophin and placental lactogen release from human term placental explants

Abstract

This study investigates whether albumin, a major plasma protein in direct contact with the trophoblast in vivo, can modulate human chorionic gonadotrophin (HCG) and human placental lactogen (HPL) releases from placental explants. Incubating explants with a near physiological, i.e. 5%, concentration of human or bovine albumin during 30 min increased HCG and HPL release by at least 150%. This albumin effect was not mediated by any difference in hormone adsorption onto glass surfaces. In contrast to the sustained stimulation of hormone releases elicited by the addition of 10 mmol/l extracellular calcium, the albumin-mediated secretory responses were transient. However, the albumin- and calcium-stimulatory effects were abolished at 4 degrees C, depressed by 0.36 mmol/l cycloheximide or 1 mmol/l colchicine and potentiated by 40 micromol/l cytochalasin B. Moreover, the stimulatory effect of albumin on the hormone releases was not modified in the absence of Ca(2+) or in the presence of 1 or 10 mmol/l Ca(2+) in the extracellular milieu. These data suggest that albumin is involved, at physiological concentration, in the secretion of HCG and HPL by human placenta. The cellular mechanism(s) underlying the albumin-mediated secretory responses may be partly different from those involved during the calcium-mediated stimulation.

Transplacental transfer and metabolism of bupropion

“…Since hCG release from tissue perfused with bupropion and in absence of HSA was not different from control placentas, it could be attributed to the effect of the added protein. Moreover, the increase in hCG release in presence of HSA observed in this report is in agreement with that reported for albumin stimulation of release of the hormone from term trophoblast explants in culture [21]. …”

Placenta-derived extracellular vesicles: their cargo and possible functions

“…Albumin has also been shown to stimulate the release of placental lactogen and human chorionic gonadotrophin from term placental explants (Cirelli et al 2001). The results of these studies and its presence as a common protein in trophoblastderived exosomes, lend support to the notion that albumin may contribute to the functions of exosomes.…”

The role of fatty acid unsaturation in minimizing biophysical changes on the structure and local effects of bilayer membranes

“…After the cells reached confluence, the media were replaced with 2 mL of control (4% fatty-acid free BSA - bovine serum albumin) or FFA (0.7 mM palmitate, oleate, or linoleate with 4% BSA) media and changed every 24 hrs. The BSA level used was close to physiological levels [28]. 0.7 mM FFAs was employed in this study because the plasma FFA levels in obese and type 2 diabetic patients have been reported to be approximately this level [29, 30, 31, 32].…”