INVOLVEMENT OF Na⁺-K⁺-2Cl⁻ COTRANSPORTERS IN HYPERTONICITY-INDUCED RISE IN INTRACELLULAR CALCIUM CONCENTRATION

Abstract

A hypertonic saline containing propylene glycol facilitates calcium (Ca²⁺) influx through voltage-dependent Ca²⁺ channels. The present study performed experiments to elucidate the mechanism by which Na⁺-K⁺-2Cl⁻ cotransporters participate in the rise in the intracellular calcium concentration ([Ca²⁺]i) under the hypertonic condition. Both furosemide and ethacryonic acid significantly decreased the [Ca²⁺]i raised by hypertonicity. Similarly, Na⁺-, K⁺-, or Cl⁻-free saline also reduced it. Both norepinephrine and dopamine significantly enhanced the rise in [Ca²⁺]i. In conclusion, the findings obtained indicate that the Na⁺-K⁺-2Cl⁻ cotransporters evoke cell depolarization and that this depolarization raises the [Ca²⁺]i by activating voltage-dependent Ca²⁺ channels.

Keywords:

• calcium influx
• depolarization
• hypertonicity
• Na⁺-K⁺-2Cl⁻ cotransporter
• PC12 cell