17β-estradiol upregulates distinct maxi-K channel transcripts in mouse uterus

The mouse maxi-K channel transcript undergoes alternative splicing to produce isoforms differing in sensitivity to intracellular regulators. We hypothesized that 17beta-estradiol could induce myometrial maxi-K channel transcripts to differentially splice. Polymerase chain reaction demonstrated two products at site D in mice injected with either 8.5 mug of 17beta-estradiol for 4 days or a vehicle control. Splicing of site D is known to modulate the sensitivity of the maxi-K channel to calcium and voltage. RNase protection analyses revealed that the a subunit transcript, and an exon encoding 59 amino acids at site D that enhances Ca2+- and voltage-sensitivity, are upregulated similar to1.4-fold after 17beta-estradiol stimulation however, the insertless isoform, of this transcript is enhanced similar to5-fold. Immunoblotting demonstrates that the total maxi-K channel a subunit expression mimics transcript regulation. These findings verify that maxi-K channel transcripts are differentially spliced by 17beta-estradiol, which may contribute to stoichiometric changes in isoform expression during pregnancy. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.