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Specific and nonspecific effects of nucleotides on hormone‐induced phosphoinositide turnover in permeabilized human pituitary tumour cells (Flow 9000)
Author(s) -
Lo William W.Y.,
Hughes John
Publication year - 1987
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(87)80552-5
Subject(s) - nucleotide , gtp' , inositol phosphate , guanine , chemistry , agonist , biochemistry , inositol , receptor , guanosine triphosphate , biology , enzyme , gene
Previous studies have shown that agonist‐induced inositol phosphate formation in the human embryonic pituitary cell line Flow 9000 is regulated by guanine nucleotides, and it is likely that a guanine nucleotide‐binding protein is involved in coupling receptors to phosphoinositidase C (PIC) [(1986) Biochem.Soc. Trans. 14, 1135–1136]. We have now tested the specificity of various nucleotides in regulating PIC activity in the absence or presence of the hormone cholecystokinin (CCK‐8) in saponin‐permeabilized [ 3 H]inositol‐labelled Flow 9000 cells. We found that all nucleotides tested (i.e. CTP, UTP, ITP, TTP, GTP, GppNHp, GTP[S], ATP, AppNHp and ATP[S]) stimulated total [ 3 H]inositol phosphate ( 3 H]IP) formation in a dose‐dependent manner with similar potency and efficacy. However, only guanine nucleotides significantly enhanced CCK‐8 stimulation of [ 3 H]IP production. These results indicate a physiological role for guanine nucleotides in regulating hormone‐induced phosphoinositide turnover. In addition, the effects of nucleotides on calcium‐dependent PIC activity are discussed.