Glomerular Immunoglobulin Deposits Induce Glomerular Inflammation in Pregnant but not in Non‐pregnant Rats

PROBLEM: Does an inflammatory stimulus evoke a more intense inflammatory response in pregnant rats as compared with nonpregnant rats? METHOD OF STUDY: Non-pregnant rats were injected with antibodies against the glomerular basement membrane (GBM), 14 days before pregnancy, to induce a subclinical glomerulonephritis. Part of the rats were rendered pregnant, the others remained nonpregnant throughout the experiment. Two experiments were performed: in experiment 1, pregnant and non-pregnant rats were killed at various intervals after the injection with antibody and parameters characteristic of a glomerular inflammation were evaluated using immunohistology on cryostat kidney sections and liver sections. In experiment 2, 24-hr urinary protein excretion was measured at various days after the injection in pregnant and non-pregnant rats. RESULTS: Experiment 1 revealed that a significant glomerular inflammation, as characterized by increased numbers of monocytes and LFA-1 positive cells per glomerulus, was only observed in pregnant rats with glomerulonephritis. Experiment 2 revealed that only pregnant rats with glomerulonephritis showed increased urinary protein excretion. CONCLUSION: The fact that glomerular inflammation coincides with proteinuria only in pregnant rats with glomerulonephritis, may suggest that these phenomena are causally related and promoted by the pregnant condition.