Renal cortical release of a specific macrophage chemoattractant in response to ureteral obstruction

Acute ureteral obstruction results in a large influx of macrophages into the cortex and medulla of the obstructed kidney. We examined supernatants from short-term cultures of acutely obstructed and contralateral control renal cortices to determine whether differential production of a chemoattractant for macrophages could account for the cellular infiltrate observed in the obstructed kidney. Using a microchemotaxis assay, supernatants from obstructed renal cortex did demonstrate significantly more chemotactic activity for rat peritoneal macrophages than did supernatants from the contralateral kidneys. This activity showed a dose-response relationship with macrophage migration, peaked between 4 and 12 hours of obstruction, and declined with longer periods of obstruction. The activity was heat stable. It was retained by an octadecylsilane column, and eluted with methanol. Partitioning of the methanol fraction into aqueous and organic phases demonstrated significant activity in the organic phase. In summary, the acutely obstructed rat kidney releases a previously undescribed chemotactic factor that behaves as a lipid. This factor may account for the mononuclear cell infiltrate observed during obstruction.