Cholecystokininの膵外分泌刺激作用におけるguanine nucleotide制御蛋白質の役割に関する研究 (第2報):コレラ毒素及び, 百日咳毒素の効果

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We have recently shown that F- can mimic the actions of cholecystokinin (CCK) on amylase release, Ca2+ mobilization and inositol phosphate generation in pancreatic acinar cells. We have concluded, therefore, that pancreatic CCK receptors may be coupled to the activation of polyphosphoinositide hydrolysis by a guanine nucleotide regulatory protein (N protein), which seems to be sensitive to F-. In the present study, in order to further characterize this N protein coupled to pancreatic CCK receptors, we have examined the effects of bacterial toxins, pertussis toxin (PT) and cholera toxin (CT) on both CCK-and NaF-induced cellular responses in isolated rat pancreatic acini. Neither PT or CT pretreatment of acini affected both CCK-and NaF-stimulated increases in intracellular Ca2+ concentration monitored by quin2. Furthermore, pretreatments of acini with PT and CT didn't alter the effects of CCK on inositol phosphate generation in acini. Similarly, NaF-induced inositol phosphate generation was not changed by these toxin treatments. However, pretreatment procedures employed in this study were considered to catalize complete ADP-ribosylation of α-subunit of the stimulatory (Ns) and inhibitory (Ni) N protein. These results, therefore, strongly suggest that a N protein coupling pancreatic CCK receptors to the breakdown of polyphosphoinositide may be distinct from Ns or Ni like protein.
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