Functional Expression Profile of Voltage-Gated K(+) Channel Subunits in Rat Small Mesenteric Arteries.
Multiple K v channel complexes contribute to total K v current in numerous cell types and usually subserve different physiological functions. Identifying the complete compliment of functional K v channel subunits in cells is a prerequisite to understanding regulatory function. It was the goal of this work to determine the complete K v subunit compliment that contribute to functional K v currents in rat small mesenteric artery (SMA) myocytes as a prelude to studying channel regulation. Using RNA prepared from freshly dispersed myocytes, high levels of K v 1.2, 1.5, and 2.1 and lower levels of K v 7.4 α-subunit expressions were demonstrated by quantitative PCR and confirmed by Western blotting. Selective inhibitors correolide (K v 1; COR), stromatoxin (K v 2.1; ScTx), and linopirdine (K v 7.4; LINO) decreased K v current at +40 mV in SMA by 46 ± 4, 48 ± 4, and 6.5 ± 2 %, respectively, and K v current in SMA was insensitive to α-dendrotoxin. Contractions of SMA segments pretreated with 100 nmol/L phenylephrine were enhanced by 27 ± 3, 30 ± 8, and 7 ± 3 % of the response to 120 mmol/L KCl by COR, ScTX, and LINO, respectively. The presence of K v 6.1, 9.3, β1.1, and β1.2 was demonstrated by RT-PCR using myocyte RNA with expressions of K vβ1.2 and K v 9.3 about tenfold higher than K vβ1.1 and K v 6.1, respectively. Selective inhibitors of K v 1.3, 3.4, 4.1, and 4.3 channels also found at the RNA and/or protein level had no significant effect on K v current or contraction. These results suggest that K v current in rat SMA myocytes are dominated equally by two major components consisting of K v 1.2-1.5-β1.2 and K v 2.1-9.3 channels along with a smaller contribution from K v 7.4 channels but differences in voltage dependence of activation allows all three to provide significant contributions to SMA function at physiological voltages.
Program in Cardiovascular Disease, Lankenau Institute for Medical Research, Main Line Health System, 100 Lancaster Avenue, Wynnewood, PA, 19096, USA. coxr@mlhs.org.
Robert H
http://orcid.org/0000-0001-8884-9540
RH
Cox
Program in Cardiovascular Disease, Lankenau Institute for Medical Research, Main Line Health System, 100 Lancaster Avenue, Wynnewood, PA, 19096, USA.
Samantha
S
Fromme
D000818:Animals; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008638:Mesenteric Arteries / Q000033:anatomy & histology / Q000378:metabolism*; D009929:Organ Size; D009928:Organ Specificity; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics*; D021122:Protein Subunits / Q000235:genetics*; D051381:Rats; D017208:Rats, Wistar
D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits
Contractile effects; Gene expressions; K v currents; K v subunits; Protein expression; Smooth muscle cells; Toxin inhibitors