Evidence for receptor-mediated calcium entry and refilling of intracellular calcium stores in FRTL-5 rat thyroid cells

✍ Scribed by Kid Törnquist

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 824 KB
• Volume: 150
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041500113

✦ Synopsis

The aim of the present study was to investigate the relationship between agonist-induced changes in intracellular free CaL+ ([Ca"],) and the refilling of intracellular CaLc stores in Fura 2-loaded thyroid FRTL-5 cells. Stimulating the cells with ATP induced a dose-dependent increase in ([Gal-' 1,). The ATP-induced increa5e in [Ca"], was dependent on both release of sequestered intracellular CaL+ as well as influx of extracellular CaL+. Addition of Ni'+ prior to ATP blunted the component of the ATP-induced increase in ICa2'], dependent on influx of Ca2+. In cells stimulated with ATP in a CaL+-free buffer, readdition of CaL+ induced a rapid increase in [Ca'+l,; this increase was inhibited by Ni'+. In addition, the ATP-induced influx of 45Ca2 ' was blocked by NiLf. Stimulating the cells with noradrenaline (NA) also induced release of sequestered Cali and an influx of extracellular CaLf. When cells were stimulated first with NA, a subsequent addition of ATP induced a blunted increase in [Ca"],. If the action of NA was terminated by addition of prazosin, and ATP was then added, the increase in ICa"], was restored to control levels. Addition of N i l + prior to prazosin inhibited the restoration of the ATP response. In the presence of extracellular Md', ATP stimulated quenching of Fura 2 fluorescence. The quenching was probably due to influx of Mn2', as it was blocked by Ni'+. The results thus suggested that stimulating release of sequestered CaL+ in FRTL-5 cells was followed by influx of extracellular Ca'+ and rapid refilling of intracellular Ca'+ stores.