Endothelin association with the cultured rat Kupffer cell: Characterization and regulation

✍ Scribed by Katherine Stephenson; Stephen A. K. Harvey; Shamimunisa B. Mustafa; Ann T. Eakes; Merle S. Olson

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 1009 KB
• Volume: 22
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.1840220330

✦ Synopsis

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 athophysiology. We measured the surface binding of [' IIET-1 to rat Kupffer cells in primary culture at 4°C; the apparent dissociation constant (&) was 270 pmoVL, and the apparent B,, was 3,000 receptordcell. 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 & was 30 pmol/L, comparable with other reports for hepaticderived cells. Studies using ['251]ET-1, ['"QET-3, and specific ET (ant)agonists showed that Kupffer cells possess predominantly ETB type receptors. Prior treatment with 500 pmol/L unlabeled endothelin rapidly (<15 minutes) occluded W O of subsequent [Iz5I]ET association; using 5 nmoVL unlabeled ET, this occlusion occurred within 1 minute. ['2511ET association with Kupffer cells was unaffected by short-term (=l hour) treatment with cyclic adenosine monophosphate (CAMP), but long-term (20 hour) treatment resulted in a twofold increase in ['=r]ET association with no change in the apparent &. Stimulation of protein kinase C in Kupffer cells by phorbol 12myristate acetate had a dual regulatory effect on ['251]ET association. Short-term (< 1 hour) treatment with phor-bol12-myristate acetate decreased ['25rJET-3 association by 509/,, whereas prolonged treatment (20 hour) increased association twofold. In both cases, the apparent & for [lUIl-endothelin was unaltered. (HEPATOLOGY Endothelin (ET) is a potent vasoactive peptide that exhibits biological effects in numerous tissues. l-' On administration of ['2511ET into the circulation of rats, ~1 2 % of the radiolabeled peptide localizes in the ! 2 1995;22:896-905.