The effects of pyridine nucleotides on the activity of a calcium-activated nonselective cation channel in the rat insulinoma cell line, CRI-G1.
The activity of a calcium-activated nonselective (Ca-NS+) channel in a rat insulinoma cell line (CRI-G1) is inhibited by pyridine nucleotides in excised patches. The effects of all four pyridine nucleotides tested, beta-NAD+, beta-NADH, beta-NADP+ and beta-NADPH were very similar when tested at 0.1 mM, and at 1 mM the phosphorylated forms, beta-NADP+ and beta-NADPH, appeared to be slightly more potent than beta-NAD+ and beta-NADH. All the pyridine nucleotides tested reduced both the open state probability of the channel and the number of functional channels observed in a single patch. The application of beta-NAD+, but not of the other nucleotides tested, to the cytoplasmic surface of isolated inside-out patches from CRI-G1 cells opened a novel nonselective cation channel (the beta-NAD(+)-NS+ channel). The activity of this new channel is calcium sensitive and may also be inhibited by AMP.
Reale
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V
Department of Clinical Biochemistry, University of Cambridge, New Addenbrookes Hospital, United Kingdom.
Hales
C N
CN
Ashford
M L
ML
D000818:Animals; D002118:Calcium / Q000502:physiology*; D007340:Insulinoma / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D009243:NAD / Q000494:pharmacology*; D009249:NADP / Q000494:pharmacology*; D010190:Pancreatic Neoplasms; D018408:Patch-Clamp Techniques; D051381:Rats; D014407:Tumor Cells, Cultured
D007473:Ion Channels; D009243:NAD; D009249:NADP; D002118:Calcium