EFFECT OF MORPHINE ON MESANGIAL IMMUNOGLOBULIN-G AGGREGATE KINETICS

Because mesangial expansion is considered a precursor of focal glomeru losclerosis, we studied whether morphine can cause mesangial expansion . We used radiolabeled human immunoglobulin G aggregates (I-125-ahIgG) to study mesangial kinetics in control and experimental (morphine-tre ated) rats. Control and experimental rats were administered I-125-ahIg G by tail vein. Serum levels of I-125-ahIgG and uptake of I-125-ahIgG by liver, spleen, and mesangium were determined at 4, 8, 12, 24, and 3 6 h after I-125-ahIgG administration. Mesangial I-125-ahIgG levels wer e higher (P < 0.05) at 4 h and at later periods in morphine-treated vs . control rats. Naloxone, an opioid antagonist, did not attenuate the morphine-induced mesangial accumulation of I-125-ahIgG. The mean uptak e of IgG aggregates was lower in the liver and spleen of morphine-trea ted rats at 36 h (P < 0.05). In both in vivo and in vitro experiments, ultrastructural studies showed accumulation of IgG-coated gold partic les in vesicles, endosomes, and lysosomes. Morphine may have increased the accumulation of I-125-ahIgG in the glomeruli either by increasing the delivery of macromolecules into the mesangium or by altering the exit of macromolecules from the mesangium.