Thrombin Activates the Sarcolemmal Na+-H+Exchanger

• DOI: 10.1161/01.res.79.4.705
• Publication Date: 2012-06-12T00:47:05Z
• Authors: Masahiro Yasutake; Robert S. Haworth; Anna King; Metin Avkiran
• Keywords: Sarcolemma

Thrombin can activate the plasma membrane Na + -H exchanger in a variety of noncardiac cells. We have studied (1) effect thrombin on activity sarcolemmal freshly isolated quiescent ventricular myocytes from adult rat heart and (2) signaling mechanism(s) underlying any effect. Reverse-transcription polymerase chain reaction analysis revealed receptor mRNA expression myocyte-enriched cell preparation. As an index activity, acid efflux rates ( J H s) were determined single (n=4 to 11 per group) loaded with pH-sensitive fluoroprobe carboxy-seminaphthorhodafluor-1 after two consecutive intracellular pulses (induced by transient exposure 20 mmol/L NH 4 Cl) bicarbonate-free medium. At pH i 6.9, did not change significantly during second pulse relative first control However, when occurred presence 0.2, 1, or 5 U/mL thrombin, increased 30%, 62% P <.05), 87% respectively. A hexameric receptor–activating peptide (SFLLRN) mimicked 73% <.05) at 25 μmol/L. In contrast, inactive (FLLRN) was without cells pretreated 100 nmol/L GF109203X μmol/L chelerythrine (protein kinase C inhibitors), neither nor SFLLRN produced significant increase . 10 HOE-694 (a inhibitor), recover load, even SFLLRN, confirming that primary mechanism under conditions used. Neither affected resting Ca 2+ background loading. conclude express functional receptor, whose stimulation results exchanger, this appears occur through protein C–mediated mechanism.