Local production of inflammatory mediators in an experimental model of acute obstructive pyelonephritis.

To investigate bacterial growth and inflammatory mediator release in the early stage of the immune response, a unilateral acute ascending pyelonephritis was induced in rats by intrabladder inoculation of Escherichia coli. The infected left kidney showed a significant bacterial proliferation, local production of interleukin (IL)-6 and IL-8 as detected by immunocytochemistry, and extensive destruction of renal parenchyma associated with impressive leukocyte recruitment. Inducible and constitutive nitric oxide synthases (NOS) were locally expressed, and a time-dependent increase in urinary secretion of nitric oxide (NO) was seen that could be blocked by NG-monomethyl-L-arginine. However, there was a discrepancy between the NO profile in the kidney and urine. The results demonstrate that in the early stage of acute pyelonephritis kidney tubules participate actively in the local host response by producing important inflammatory mediators and that urinary NO levels are not suitable for predicting renal NOS activity.