Transport of charged solutes by the syncytiotrophoblast, which separates maternal and fetal circulations, is driven in part by electrochemical gradients, a determinant of which is membrane potential (Greenwood et al. 1996). TASK and TREK are members of the mammalian tandem-pore domain K⁺ channel family that play a role in determining resting membrane potential and potentially K⁺ homeostasis in non-excitable cells (Lesage & Lazdunski, 2000). Placental K⁺ homeostasis is likely to be an important factor in determining net solute and nutrient transfer to the fetus, therefore expression of molecules participating in K⁺ movement are of interest. The aim of this study was to determine mRNA expression of TASK and TREK in two trophoblast models: primary cultured cytotrophoblast cells and choriocarcinoma cell lines.

Cytotrophoblast cells were isolated from human term placentas from normal pregnancies (Greenwood et al. 1996). Placentas were taken with informed written consent and according to local ethical committees’ regulations. Three separate cytotrophoblast cell isolations cultured for 18 (mononucleate) and 66 h (multinucleate), and three different passages of placental choriocarcinoma cell lines (JAr, JEG and BeWo) were used. Total RNA was extracted and quantified using standard techniques. RT-PCR was performed using gene-specific primers for TASK1 to 5 and TREK1 and 2 that amplified products of correct sizes (relative to a molecular ladder) when validated with control cDNA.

TASK1 was detectable in cytotrophoblasts at 18 (2/3 samples) and 66 h (3/3 samples) as was TASK2 (2/3 samples at 18 hours, 3/3 samples at 66 hours). TASK2 was observed in all choriocarcinoma cell lines (3/3 samples per cell line) contrasting with TASK1 whose signal was variable. TASK3 was detected in most samples. TASK4 was detected in all cytotrophoblast samples, JAr and BeWo cells with variable intensity. TASK5 was visible in 18 and 66 h cytotrophoblasts (2/3 samples for each) as well as BeWo cells (3/3 samples). TREK1 was observed in 18 and 66 h cytotrophoblasts (2/3 samples for each), as well as JAr (2/3 samples), JEG (3/3 samples) and BeWo (1/3 samples) cells. TREK2 was detected in all three choriocarcinoma cell lines but not cytotrophoblasts.

These data indicate different patterns of gene expression for TASK and TREK isoforms between cytotrophoblasts and choriocarcinoma cell lines.

This work was supported by Tommy’s, the baby charity.