M. Kondo et al., EFFECT OF PLATELET-ACTIVATING-FACTOR ON INTRACELLULAR FREE CALCIUM INCOW TRACHEAL EPITHELIUM, American journal of respiratory cell and molecular biology, 10(3), 1994, pp. 278-283
The effect of platelet activating factor (PAF) on the intracellular cy
tosolic levels of free calcium ([Ca2+](i)) was studied in cultured epi
thelium 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-depende
nt 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 af
ter addition and a subsequent sustained elevation that reached a plate
au after 1 min. The potency for the sustained response was greater by
approximately 1 log U than that for the transient response. Preincubat
ion of the cells with the PAF receptor antagonist CV6209 (10(-6) M) in
hibited the increase in [Ca2+](i). Ca2+-free medium (2 mM EGTA) totall
y abolished the sustained response to PAF, but it only partially inhib
ited the transient response. Verapamil (10(-5) M) also largely inhibit
ed the sustained response. Moreover, PAF transiently increased inosito
l triphosphate (IP3) levels, peaking 10 s after addition. These data s
uggest that (1) a PAF-induced increase in [Ca2+](i) is mediated via PA
F receptors, (2) PAF causes both transient [Ca2+](i) release from intr
acellular stores through IP3 production and sustained [Ca2+](i) influx
from extracellular solution, and (3) Ca2+ influx may be a major pathw
ay of PAF-induced increase in [Ca2+](i) in cow tracheal epithelium.