Rapid disappearance from serum of intravenously injected rat myeloma IgA and its secretion into bile

Abstract

Intravenously injected monoclonal rat IgA is first removed from rat serum at a very fast rate (93% in 4 h), then at a much slower rate (t/2 = 24 h). The rapid initial disappearance is thought to be due in part to secretion into rat bile. This was demonstrated by rat liver perfusions with semisynthetic medium containing diluted (1:200) IgA myeloma serum. During perfusion, the cannulated bile displayed increasingly high levels of this IgA, with a bile to medium ratio of 38 after 1 h of perfusion; at the same time, there was a 40% drop of the rat monoclonal IgA concentration in the medium, which was not observed for rat IgG_2a and albumin. All of the monoclonal biliary IgA was bound to secretory component. The rat liver is thus able to actively secrete a monoclonal IgA from the circulation into bile against a strong concentration gradient.