Effects of calmodulin antagonists on calcium pump and cytosolic calcium level in human neutrophils.
The concentration of cytosolic free calcium was monitored in suspensions of intact human neutrophils in phosphate-buffered saline by means of the fluorescent indicator Indo 1 trapped in the cytosol. Trifluoperazine and n-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide markedly reduced the amplitude of the transient increase in cytosolic Ca2+ triggered by CaCl2 as well as by N-formyl-methionyl-leucyl-phenylalanine. The effect of the calmodulin antagonists on the calcium burst observed upon cell activation was much more pronounced in the presence of extracellular free calcium than in EGTA-containing media; it was not inhibited by wortmannin or thapsigargin. Nevertheless, trifluoperazine and n-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide inhibited the plasma-membrane Ca2+ ATPase if added to plasma membrane-enriched fractions of neutrophils. These results suggest that calmodulin antagonists affect calcium ion influx even if they inhibit plasma membrane Ca2+ ATPase.
Capuozzo
E
E
Department of Biochemical Sciences, University of Rome La Sapienza and C.N.R. Center of Molecular Biology, Italy.
Verginelli
D
D
Crifò
C
C
Salerno
C
C
D002118:Calcium / Q000032:analysis*; D002122:Calcium Chloride / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002462:Cell Membrane / Q000187:drug effects; D003600:Cytosol / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007211:Indoles; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology
D002147:Calmodulin; D007211:Indoles; D013449:Sulfonamides; D014268:Trifluoperazine; C017967:W 7; D000252:Calcium-Transporting ATPases; D002122:Calcium Chloride; C048960:indo-1; D002118:Calcium