Hormonal control of protein expression and mRNA levels of the MaxiK channel alpha subunit in myometrium.

Large conductance voltage-dependent and Ca(2+)-modulated K(+) channels play a crucial role in myometrium contractility. Western blots and immunocytochemistry of rat uterine sections or isolated cells show that MaxiK channel protein signals drastically decrease towards the end of pregnancy. Consistent with a transcriptional regulation of channel expression, mRNA levels quantified with the ribonuclease protection assay correlated well with MaxiK protein levels. As a control, Na(+)/K(+)-ATPase protein and RNA levels do not significantly change at different stages of pregnancy. The low numbers of MaxiK channels at the end of pregnancy may facilitate uterine contraction needed for parturition.