Characterization of calcium signaling pathways in human preadipocytes

Intracellular free Ca²⁺ (Ca) is an important regulator of many cellular activities; however, Ca²⁺ signaling is not well studied in human preadipocytes. The purpose of the present study was to characterize Ca²⁺ signal pathways using a confocal scanning technique and RT‐PCR. It was found that spontaneous Ca oscillations were observed in 12.1% preadipocytes, and number of cells with Ca²⁺ oscillations was increased to 47.9% by 1% fetal bovine serum. Ca oscillations were dependent on Ca²⁺ entry mainly via stored‐operated Ca²⁺ (SOC) entry. They were suppressed by the SOC entry channel blocker La³⁺, the phospholipase C (PLC) inhibitor U73122, the inositol trisphosphate receptor (IP3R) blocker 2‐amino‐ethoxydiphenyl borate, or the sarcoplasmic/endoplasmic reticulum Ca²⁺ pump (SERCA) inhibitors thapsigargin and cyclopiazonic acid, but not by ryanodine. The IP3R activator thimerosal increased Ca oscillations. In addition, the plasma membrane Ca²⁺ pump (PMCA) inhibitor carboxyeosin and Na⁺–Ca²⁺ exchanger (NCX) inhibitor Ni²⁺ both suppressed Ca²⁺ oscillations. RT‐PCR revealed that the mRNAs for IP3R1‐3, SERCA1,2, NCX3 and PMCA1,3,4, Ca_V1.2, and TRPC1,4,6, STIM1 and Orai1 (for SOC entry channels) were significant in human preadipocytes. The present study demonstrates that multiple Ca²⁺ signal pathways are present in human preadipocytes, and provides a basis for investigating how Ca²⁺ signals regulate biological and physiological activities of human preadipocytes. J. Cell. Physiol. 220: 765–770, 2009. © 2009 Wiley‐Liss, Inc.