| Summary: | 碩士 === 長庚醫學暨工程學院 === 基礎醫學研究所 === 85 === In this study, the experiments were conducted to characterize
the P2 receptor subtype coupling to signal transduction on
tracheal epithelial cells (TECs). The nucleotides ATP and UTP
caused a concentration-dependent increase in inositol
phosphates (IPs) accumulation and calcium mobilization.The rank
orderof agonist potency was ATP = UTP >> 2-methylthio ATP
(2-MeSATP) = alpha,beta-methylene ATP (alpha,beta-MeATP).
Stimulation of TECs with maximallyeffectiveconcentrations of ATP
and UTP showed no additive effect. ATP andUTP induced mutual
cross-desensitization in IPs accumulation and
calciummobilization.These findings suggest that both ATP and UTP
act upon a commonnucleotide receptor defined as P2Y2 (P2U)
receptor. Pretreatment of TECs withpertussis toxin and cholera
toxin had no effect on ATP- and UTP-induced IPsaccumulationand
calcium mobilization. Incubation of TECs in the absence of
external Ca2+, caused a decrease in IPs accumulation and calcium
mobilzationevoked by ATP, UTP. In contrast, omission of Mg2+
from buffer did not signi-ficantly change IPs response to ATP
and UTP. The IPs accumulation and [Ca2+]iincrease in response to
ATP and UTP were inhibited by Ni2+. Prior treatment with
staurosporine, a protein kinase C inhibitor, reversed the effect
of PMAon the ATP- and UTP-induced signal transduction. The
effect of PMA was due tothe inhibition of G protein(s) or
phospholipase C activity or uncoupled Gprotein(s) from PLC. It
revealed that TECs expressed PKC alpha, betaI, betaII,gamma,
epsilon, theta, delta, and zeta. With PMA treatment of cells for
various times, translocation of PKC alpha, betaI, betaII, gamma,
epsilon, theta,and delta from cytosol to the membrane was seen
after treatment.
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