Activation of Na+/H+ exchange is unnecessary in the induction of c-fos mRNA in serum-stimulated vascular smooth muscle cells.
1. The effects of extracellular Na+ concentration ([Na+]o) on serum-stimulated c-fos mRNA induction in vascular smooth muscle cells (VSMC) were studied to examine whether the activation of Na+/H+ exchange and the following intracellular alkalinization are necessary in the induction of c-fos in VSMC. 2. When monitored with 2', 7'-bis (carboxylethyl)-5(6)-carboxyfluorescein, the reduction in [Na+]o in HCO(3-)-free buffer caused a dose-dependent inhibition of Na(+)-dependent intracellular pH recovery in acid-loaded VSMC. In addition, serum-stimulated intracellular alkalinization in VSMC was completely blocked by the removal of extracellular Na+. 3. By contrast, c-fos induction, quantified by slit blot hybridization of c-fos mRNA, was not fully inhibited by the reduction of [Na+]o. Furthermore, amiloride and ethylisopropyl-amiloride, inhibitors of Na+/H+ exchange, only partially blocked c-fos induction by serum. 4. We concluded from the observation above, that the intracellular alkalinization caused by the activation of Na+/H+ exchange was unnecessary in serum-stimulated induction of c-fos mRNA in VSMC.
Nabika
T
T
Department of Laboratory Medicine, Shimane Medical University, Izumo, Japan.
Kobayashi
A
A
Nara
Y
Y
Endo
J
J
Yamori
Y
Y
D000818:Animals; D001769:Blood; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D012333:RNA, Messenger / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D015398:Signal Transduction; D012964:Sodium / Q000008:administration & dosage / Q000494:pharmacology
D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D012964:Sodium