Effects of atrial natriuretic peptide and cGMP on uptake of IgG complexes by macrophages

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Abstract
Macromolecular handling by macrophages and glomerular mesangial cells may be important in the development of renal injury. We undertook the present study to determine whether atrial natriuretic peptide (ANP), a particulate guanylate cyclase stimulator, plays a direct role in uptake of immunoglobulin G (IgG) complexes by macrophages. Macrophages incubated with ANP at 10(-5) and 10(-6) M showed significantly suppressed uptake of IgG complexes compared with control. Macrophage uptake of IgG complexes was also significantly suppressed by the soluble guanylate cyclase stimulator sodium nitroprusside. Dibutyryl guanosine 3',5'-cyclic monophosphate and dibutyryl adenosine 3',5'-cyclic monophosphate both significantly suppressed IgG complex uptake as well. ANP was found to significantly enhance macrophage guanosine 3',5'-cyclic monophosphate (cGMP) levels compared with control cells, and this effect was antagonized by angiotensin II. Angiotensin II significantly enhanced uptake of IgG complexes and suppressed macrophage adenosine 3',5'-cyclic monophosphate synthesis, and both effects were antagonized by coincubation with ANP. These results suggest that ANP modulates uptake of IgG complexes by macrophages and that this effect may be mediated via cGMP.