Downregulation of large-conductance Ca2+-activated K+ channels in human umbilical arterial smooth muscle cells in gestational diabetes mellitus

Aims We investigated the changes in large-conductance Ca2+-activated K+ (BKCa) channels from human umbilical arterial smooth muscle cells experiencing gestational diabetes mellitus (GDM). Main methods Whole-cell patch-clamp technique, arterial tone measurement, RT-PCR, Quantitative real-time PCR, western blot were performed in human umbilical arterial smooth muscle cells. Key findings Whole-cell BKCa current density was decreased in the GDM group compared with the normal group. The vasorelaxant effects of the synthetic BKCa channel activator NS-1619 (10 μM) were impaired in the GDM group compared with the normal group. Reverse-transcription polymerase chain reaction (RT-PCR), real-time RT-PCR, and western blot analyses suggested that the mRNA, total RNA, and protein expression levels of the BKCa channel were decreased in the GDM group relative to the normal group. In addition, the expression levels of protein kinase A and protein kinase G, which regulate BKCa channel activity, remained unchanged between the groups. Applying the BKCa channel inhibitor paxilline (10 μM) induced vasoconstriction and membrane depolarization of isolated umbilical arteries in the normal group but showed less of an effect on umbilical arteries in the GDM group. Significance Our results demonstrate for the first time impaired BKCa current and BKCa channel-induced vasorelaxation activities that were not caused by impaired BKCa channel-regulated protein kinases, but by decreased expression of the BKCa channels, in the umbilical arteries of GDM patients.