Regulation of the cytosolic pH set point for activation of the Na+/H+antiport in human platelets: the roles of the Na+/Ca2+exchange, the Na+-K+-2Cl−cotransport and cellular volume

✍ Scribed by Masayuki Kimura; Abraham Aviv

• Publisher: Springer
• Year: 1993
• Tongue: English
• Weight: 748 KB
• Volume: 422
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00374006

✦ Synopsis

To explore further the mechanisms that regulate the Na+/H + antiport in human platelets, we examined the effect of Na + pump inhibition by ouabain and K + removal from the extracellular medium on parameters of this transport system. Treatment with ouabain resulted in increased cytosolic free Ca 2+ and Na +, coupled with an alkaline shift in the cytosolic pH set point for the Na + / H + antiport. Inhibition of the Na + pump by the removal of K + from the medium increased the cytosolic Na + but not the cytosolic Ca 2 + ; yet this treatment also produced a substantial alkaline shift in the cytosolic pH set point for the Na+/H + antiport. This effect appeared to relate to a decline in cellular volume and it was attenuated by the Na +-K +-2 C1-cotransport inhibitor, bumetanide. These findings indicate: (a) a link between the Na + pump and the Na+/H + antiport, mediated by the Na+/Ca 2+ exchange and the cytosolic free Ca 2 +, and (b) a link between the Na+/H + antiport and the Na+-K+-2C1cotransport through cellular volume.