Contractile regulation of the Na+-K+-2Cl(-) cotransporter in vascular smooth muscle


AKAR F., Jiang G., Paul R., O'Neill W.

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, vol.281, no.2, 2001 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 281 Issue: 2
  • Publication Date: 2001
  • Doi Number: 10.1152/ajpcell.2001.281.2.c579
  • Journal Name: AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: sodium-potassium-2-chloride cotransport, myosin light chain kinase, phenylephrine, contraction, LIGHT-CHAIN PHOSPHORYLATION, 2,3-BUTANEDIONE MONOXIME, PROTEIN-PHOSPHORYLATION, ENDOTHELIAL-CELLS, RAT AORTA, IN-VITRO, MYOSIN, KINASE, ACTIVATION, VOLUME
  • Gazi University Affiliated: No

Abstract

Vasoconstrictors activate the Na+-K+-2Cl(-) cotransporter NKCC1 in rat aortic smooth muscle, but the mechanism is unknown. Efflux of Rb-86(+) from rat aorta in response to phenylephrine (PE) was measured in the absence and presence of bumetanide, a specific inhibitor of NKCC1. Removal of extracellular Ca2+ completely abolished the activation of NKCC1 by PE. This was not due to inhibition of Ca2+-dependent K+ channels since blocking these channels with Ba2+ in Ca2+-replete solution did not prevent activation of NKCC1 by PE. Stimulation of NKCC1 by PE was inhibited 70% by 75 muM ML-9, 97% by 2 muM wortmannin, and 70% by 2 mM 2,3-butanedione monoxime, each of which inhibited isometric force generation in aortic rings. Bumetanide-insensitive Rb+ efflux, an indication of Ca2+-dependent K+ channel activity, was reduced by ML-9 but not by the other inhibitors. Stretching of aortic rings on tubing to increase lumen diameter to 120% of normal almost completely blocked the stimulation of NKCC1 by PE without inhibiting the stimulation by hypertonic shrinkage. We conclude that activation of the Na+-K+-2Cl(-) cotransporter by PE is the direct result of smooth muscle contraction through Ca2+-dependent activation of myosin light chain kinase. This indicates that the Na+-K+-2Cl(-) cotransporter is regulated by the contractile state of vascular smooth muscle.