PT  - JOURNAL ARTICLE
AU  - Se-Ne Huang
AU  - Peter W. Swaan
TI  - Riboflavin Uptake in Human Trophoblast-Derived BeWo Cell Monolayers: Cellular Translocation and Regulatory Mechanisms
DP  - 2001 Jul 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 264--271
VI  - 298
IP  - 1
4099  - http://jpet.aspetjournals.org/content/298/1/264.short
4100  - http://jpet.aspetjournals.org/content/298/1/264.full
SO  - J Pharmacol Exp Ther2001 Jul 01; 298
AB  - Riboflavin (vitamin B2) is essential for fetal development and must be acquired from maternal sources. The uptake mechanism of riboflavin and the major regulatory pathways involved were characterized in a model for the placental barrier, the human choriocarcinoma cell line, BeWo. Uptake of [3H]riboflavin was saturable (Kt = 1.32 ± 0.68 nM, Jmax = 266.63 ± 26.89 fmol/mg of protein/20 min), and was significantly reduced at low temperature and in the presence of metabolic inhibitors (azide, 2-deoxyglucose) or structural analogs. Ouabain, amiloride, sodium-free buffers, and medium with pH values ranging from 3 to 8 did not affect uptake of [3H]riboflavin. In contrast, substitution of chloride with other monovalent anions significantly inhibited its uptake. Induced differentiation of BeWo cells into syncytiotrophoblasts by forskolin or 8-bromo-cyclic adenosine monophosphate introduced a time-dependent decrease of riboflavin uptake. Preincubation with activators of cyclic nucleotide-dependent protein kinase pathways (3-isobutyl-1-methylxanthine andp-chlorophenylthio-cyclic guanosine monophosphate) and calmodulin antagonists (calmidazolium and W-13) resulted in a concentration-dependent reduction of [3H]riboflavin uptake, whereas specific modulators of protein kinase C pathways did not have significant effects. 3-Isobutyl-1-methylxanthine exerted its regulatory effect on riboflavin uptake via decreasing bothKt and Jmax of the riboflavin uptake process (Kt = 6.32 ± 1.29 nM, Jmax = 135.57 ± 10.42 fmol/mg of protein/20 min). In summary, we report the presence of high- affinity riboflavin transporter(s) on the microvillous membrane of BeWo cells that appears to be modulated by cellular cyclic nucleotide levels and calmodulin. The American Society for Pharmacology and Experimental Therapeutics