Characterization of calcium signaling pathways in human preadipocytes

Intracellular free Ca 2+ (Ca   i 2+ ) is an important regulator of many cellular activities; however, Ca 2+ signaling is not well studied in human preadipocytes. The purpose of the present study was to characterize Ca 2+ signal pathways using a confocal scanning technique and RT‐PCR. It was found that spontaneous Ca   i 2+oscillations were observed in 12.1% preadipocytes, and number of cells with Ca 2+ oscillations was increased to 47.9% by 1% fetal bovine serum. Ca   i 2+oscillations were dependent on Ca 2+ entry mainly via stored‐operated Ca 2+ (SOC) entry. They were suppressed by the SOC entry channel blocker La 3+ , the phospholipase C (PLC) inhibitor U73122, the inositol trisphosphate receptor (IP3R) blocker 2‐amino‐ethoxydiphenyl borate, or the sarcoplasmic/endoplasmic reticulum Ca 2+ pump (SERCA) inhibitors thapsigargin and cyclopiazonic acid, but not by ryanodine. The IP3R activator thimerosal increased Ca   i 2+oscillations. In addition, the plasma membrane Ca 2+ pump (PMCA) inhibitor carboxyeosin and Na + –Ca 2+ exchanger (NCX) inhibitor Ni 2+ both suppressed Ca 2+ oscillations. RT‐PCR revealed that the mRNAs for IP3R1‐3, SERCA1,2, NCX3 and PMCA1,3,4, Ca V 1.2, and TRPC1,4,6, STIM1 and Orai1 (for SOC entry channels) were significant in human preadipocytes. The present study demonstrates that multiple Ca 2+ signal pathways are present in human preadipocytes, and provides a basis for investigating how Ca 2+ signals regulate biological and physiological activities of human preadipocytes. J. Cell. Physiol. 220: 765–770, 2009. © 2009 Wiley‐Liss, Inc.