Effect of platelet-activating factor on intracellular free calcium in cow tracheal epithelium.
The effect of platelet activating factor (PAF) on the intracellular cytosolic levels of free calcium ([Ca2+]i) was studied in cultured epithelium from cow trachea. In fura-2-loaded cells, PAF (10(-9) to 10(-5) M), but not lyso-PAF, increased [Ca2+]i in a concentration-dependent manner, from 106 +/- 15 to 270 +/- 40 nM (P < 0.05). This [Ca2+]i response consisted of a transient increase that peaked within 15 s after addition and a subsequent sustained elevation that reached a plateau after 1 min. The potency for the sustained response was greater by approximately 1 log U than that for the transient response. Preincubation of the cells with the PAF receptor antagonist CV6209 (10(-6) M) inhibited the increase in [Ca2+]i. Ca(2+)-free medium (2 mM EGTA) totally abolished the sustained response to PAF, but it only partially inhibited the transient response. Verapamil (10(-5) M) also largely inhibited the sustained response. Moreover, PAF transiently increased inositol triphosphate (IP3) levels, peaking 10 s after addition. These data suggest that (1) a PAF-induced increase in [Ca2+]i is mediated via PAF receptors, (2) PAF causes both transient [Ca2+]i release from intracellular stores through IP3 production and sustained [Ca2+]i influx from extracellular solution, and (3) Ca2+ influx may be a major pathway of PAF-induced increase in [Ca2+]i in cow tracheal epithelium.[1]References
- Effect of platelet-activating factor on intracellular free calcium in cow tracheal epithelium. Kondo, M., Tamaoki, J., Isono, K., Takeuchi, S., Ozawa, Y., Chiyotani, A., Konno, K. Am. J. Respir. Cell Mol. Biol. (1994) [Pubmed]
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