Experimental endotoxemia in pregnancy: in situ glomerular microthrombus formation associated with impaired glomerular adenosine diphosphatase activity.

The mechanism of increased sensitivity for endotoxin in pregnancy as reflected by the formation of microthrombi in renal glomeruli is unknown. It has been shown that reduced glomerular diphosphatase (ADPase) activity in the rat kidney greatly increases the intraglomerular thrombotic tendency. We now studied experimental intraglomerular thrombosis ex vivo in association with glomerular ADPase activity in pregnant and nonpregnant control rats after infusion of either endotoxin or saline solution. Each animal (Wistar rat) was equipped with a permanent vena jugularis catheter and received either endotoxin (1.0 micrograms/kg body weight) (n = 6) or saline solution (n = 5) 7 days before being killed; nonpregnant rats were also treated with endotoxin (n = 5) or saline solution (n = 4). On day 21, before the animals were to be killed, they were anesthetized and their left kidneys were perfused with adenosine diphosphate solution (10 micrograms/ml) and platelet-rich plasma (1 x 10(9) cells/ml). Perfused kidneys were processed for light microscopy, electron microscopy, enzyme cytochemistry at the ultrastructural level, and immunohistology. The results showed decreased ADPase activity exclusively in the glomerular basement membrane of kidneys of pregnant rats treated with endotoxin in contrast to the findings in control rats. In addition, exclusively in the group of endotoxin-treated pregnant rats, significantly increased intraglomerular platelet aggregation could be detected after alternate perfusion ex vivo. We suggest that, in the present model, enhanced susceptibility of glomerular ADPase for endotoxin is due to pregnancy-associated factors that have yet to be identified. This increased susceptibility may promote in situ formation of intraglomerular microthrombi.