Is [3H]-tiotidine a specific ligand for the H2-receptor?

Pharmacology. 1986;32(5):241-7. doi: 10.1159/000138176.

Abstract

The H2-antagonist tiotidine inhibited the H2-receptor-mediated, histamine-induced increase in cyclic AMP in dispersed mucosal cells from guinea pig stomach (Ki, 4 X 10(-8) M). The radiolabeled [3H]-tiotidine bound specifically and reversibly to the same cells with a half-maximal binding occurring at 5 X 10(-7) M tiotidine. The dissociation of bound [3H]-tiotidine from gastric cells and the Scatchard analysis of the binding binding data suggest the existence of additional binding sites for tiotidine. Eight other antagonists which inhibited the H2-receptor-mediated increase in cyclic AMP also inhibited [3H]-tiotidine binding. However, the potencies of these agents for binding did not agree with their effects on cyclic AMP. The selective H2-agonists impromidine and dimaprit which increased cyclic AMP caused only partial inhibition of [3H]-tiotidine binding. These results demonstrate that [3H]-tiotidine has limited binding to the H2-receptors and as such [3H]-tiotidine is not a suitable ligand for labelling the H2-receptor on gastric mucosal cells.

MeSH terms

  • Animals
  • Binding, Competitive
  • Cimetidine / analogs & derivatives*
  • Cimetidine / metabolism
  • Cyclic AMP / metabolism
  • Gastric Mucosa / metabolism*
  • Guinea Pigs
  • Histamine / metabolism
  • Histamine H2 Antagonists / metabolism*
  • Histamine H2 Antagonists / pharmacology
  • In Vitro Techniques
  • Male
  • Radioligand Assay
  • Receptors, Histamine / metabolism*
  • Receptors, Histamine H2 / metabolism*

Substances

  • Histamine H2 Antagonists
  • Receptors, Histamine
  • Receptors, Histamine H2
  • Cimetidine
  • Histamine
  • Cyclic AMP
  • tiotidine