PMID: 8958578Dec 3, 1996Paper

Hepatic inactivation of Leu-enkephalin

Regulatory Peptides
K L MacKinnonD Billington

Abstract

Leu-enkephalin radiolabelled at the N-terminal tyrosine by two different methods was presented to isolated perfused rat livers. Approximately 10% of a pulse of tritiated Leu-enkephalin was taken up first-pass; this was increased to 62% when the peptide was iodinated with Bolton and Hunter reagent. Uptake of both forms of radiolabelled Leu-enkephalin was inhibited by taurocholate in a concentration-dependent manner. The proportion of internalised radioactivity secreted into bile also differed but in both cases showed a very rapid time-course similar to that of [24-(14)C]taurocholate and suggestive of non-endocytic transfer via membrane transport proteins. Pre-perfusion with the aminopeptidase inhibitor bestatin increased uptake of 3H-labelled Leu-enkephalin from 10% to 23%; no further increase occurred when the endopeptidase 24.11 inhibitor thiorphan was also present. On infusion of the native peptide into rat livers, 80% of Leu-enkephalin immunoreactivity was lost between the pre- and post-hepatic perfusate; this was reduced to 65% in the presence of 10(-5) M bestatin. The almost total release of the N-terminal tyrosine from 3H-labelled Leu-enkephalin which escaped first-pass uptake confirmed that substantial sinusoidal metabol...Continue Reading

References

Jan 1, 1992·Pharmacological Research : the Official Journal of the Italian Pharmacological Society·R AldiniE Roda
May 1, 1990·Hepatology : Official Journal of the American Association for the Study of Liver Diseases·E A Jones, N V Bergasa
Jan 1, 1990·Regulatory Peptides·M M WolfeJ E McGuigan
Oct 1, 1989·Gut·J R Thornton, M S Losowsky
Oct 31, 1980·Biochemical and Biophysical Research Communications·R K Barclay, M A Phillipps
Oct 12, 1981·Biochimica Et Biophysica Acta·J M ConlonK G Alberti
Jul 1, 1994·Hepatology : Official Journal of the American Association for the Study of Liver Diseases·B StiegerL Landmann
Jul 1, 1994·Hepatology : Official Journal of the American Association for the Study of Liver Diseases·G FrickerC Thiele

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Citations

Oct 26, 1999·Hepatology : Official Journal of the American Association for the Study of Liver Diseases·E PetzingerW Kramer
Feb 17, 1999·Archives of Biochemistry and Biophysics·E CsuhaiL B Hersh

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