| Autor: |
Srinivas, S.P., Yeh, Jean Cathy, Ong, Angeline, Bonanno, Joseph A. |
| Předmět: |
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| Zdroj: |
Current Eye Research; Oct98, Vol. 17 Issue 10, p994, 11p |
| Abstrakt: |
PURPOSE. To characterize Ca[sup 2+] mobilizationby P2 receptors in the bovine corneal endothelial cells (BCEC). METHODS. Changes in intracellular Ca[sup 2+] ([Ca[sup 2+] ][sub i] ) were measured by fluorescence imaging of cultured and fresh BCECcells loaded with the Ca[sup 2+] -sensitive dye Fura-PE3. Relative ratesof Ca[sup 2+] influx were measured employing Mn[sup 2+] as a surrogatefor Ca[sup 2+] . RESULTS. Exposure of cultured cells to uridine 5′-triphosphate (UTP),2-methyl-thio ATP (msATP) and ATP caused biphasic changes in [Ca[sup 2+] ][sub i] consisting of a peak followed by a plateau phase. Based on the peakresponses to 100 μM agonist, the magnitude of UTP responses were similarto that of ATP but greater than that of msATP or ADP. UTP and msATP stimulatedMn[sup 2+] influx following [Ca[sup 2+] ][sub i] peak similarto that observed in response to cyclopiazonic acid (CPA), an inhibitor ofER Ca[sup 2+] -ATPase. Under Ca[sup 2+] -free conditions, peak responseswere similar to those in the presence of external Ca[sup 2+] , but reducedwhen the cells were pre-exposed to CPA. Reactive Blue-2 (RB2), inhibited msATPresponses by 60.4 ± 18.8% but UTP responses by only 10.6 ± 9.5%.Repeated exposures to UTP or msATP reduced [Ca[sup 2+] ][sub i] mobilizationindicating homologous desensitization. Response to UTP was not affected bya prior exposure to msATP. However, response to msATP was reduced by a priorexposure to UTP indicating mixed heterologous desensitization. Fresh cellsresponded to UTP (50 mM) with temporal characteristics of [Ca[sup 2+] ][sub i] mobilization similar to that of cultured cells. CONCLUSION. BCEC express P2 receptors belonging to the P2Y subfamily. Theemptying of the IP3-sensitive stores, leading to the initial peak in [Ca 2+ ][sub i] response, subsequently caused capacitative Ca[sup 2+] influx leading to the onset of the plateau phase. A significant homologousdesensitization to UTP and msATP, selective heterologous de... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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