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Endothelin association with the cultured rat Kupffer cell: Characterization and regulation
Author(s) -
Stephenson Katherine,
Harvey Stephen A. K.,
Mustafa Shamimunisa B.,
Eakes Ann T.,
Olson Merle S.
Publication year - 1995
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.1840220330
Subject(s) - endothelin receptor , endothelin 1 , microbiology and biotechnology , association (psychology) , medicine , chemistry , endocrinology , biology , psychology , receptor , psychotherapist
Circulating endothelin (ET) levels are elevated in conditions such as endotoxemia, hepatic ischemia‐reperfusion injury, or orthotopic liver transplantation, and this potent peptide may contribute to hepatic pathophysiology. We measured the surface binding of [ 125 I]ET‐1 to rat Kupffer cells in primary culture at 4°C; the apparent dissociation constant (K d ) was 270 pmol/L, and the apparent B max was 3,000 receptors/cell. At 37°C, total association (surface binding plus internalization) was much greater than at 4°C, indicating that internalization of the receptor‐ligand complex is rapid; the apparent K d was 30 pmol/L, comparable with other reports for hepaticderived cells. Studies using [ 125 I]ET‐1, [ 125 I]ET‐3, and specific ET (ant)agonists showed that Kupffer cells possess predominantly ET B type receptors. Prior treatment with 500 pmol/L unlabeled endothelin rapidly (<15 minutes) occluded 60% of subsequent [ 125 I]ET association; using 5 nmol/L unlabeled ET, this occlusion occurred within 1 minute. [ 125 I]ET association with Kupffer cells was unaffected by short‐term (<1 hour) treatment with cyclic adenosine monophosphate (cAMP), but long‐term (20 hour) treatment resulted in a twofold increase in [ 125 I]ET association with no change in the apparent K d . Stimulation of protein kinase C in Kupffer cells by phorbol 12‐myristate acetate had a dual regulatory effect on [ 125 I]ET association. Short‐term (<1 hour) treatment with phorbol 12‐myristate acetate decreased [ 125 I]ET‐3 association by 50%, whereas prolonged treatment (20 hour) increased association twofold. In both cases, the apparent K d for [ 125 I]‐endothelin was unaltered. (Hepatology 1995; 22:896–905.)