Effects of tetrandrine on cytoplasmic free calcium in rat neutrophils

Neutrophils (NP) cytoplasmic free Ca2+ concentrations ([Ca2+]i) under several conditions were measured with Quin 2 in rats. The process of loading Quin 2-AM into the cells followed by its hydrolysis was assured by monitoring the shift of fluorescent emission spectrum of Quin 2-AM to that of Quin 2. The resting [Ca2+]i of NP in Ca2(+)-containing and Ca2(+)-free solutions were 186 +/- 45 and 46 +/- 16 nmol/L, respectively, indicating extracellular calcium concentration ([Ca2+]0) plays an important role on [Ca2+]i. Among agents tested, prostaglandin E2 (PGE2) 100 nmol/L did not change [Ca2+]i significantly. Calcimycin 25 mumol/L, leukotriene B4(LTB4) 60 nmol/L and platelet activating factor (PAF) 10 nmol/L increased [Ca2+]i of NP in Ca2(+)-containing solution from 185 +/- 54, 175 +/- 36 and 188 +/- 54 to 814 +/- 67, 577 +/- 229 and 540 +/- 174 nmol/L, respectively. But, compound 48/80 3.2 micrograms/ml, LTB4 300 nmol/L, PAF 10 nmol/L and PAF 5 nmol/L plus LTB4 150 nmol/L did not change significantly [Ca2+]i of NP in Ca2(+)-free solution, indicating that these agonists can not release intracellularly stored Ca2+ or no stored Ca2+ in NP is available. The rises of [Ca2+]i produced by calcimycin, PAF and LTB4 were markedly inhibited by tetrandrine (Tet) 65 mumol/L. These results, as a whole, show that Tet inhibits the rises of [Ca2+]i of NP induced by calcimycin, PAF and LTB4 via decreasing Ca2+ influx. The Ca2+ antagonism in this case may be related to its anti-allergic actions.