Tetrachlorodibenzo-p-dioxin induction of renal microsomal enzyme systems: ultrastructural effects on pars recta (S3) proximal tubule cells on the rat kidney.

A single oral administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin to rats at a dose level of 25 microgram/kg produced marked proliferation of smooth endoplasmic reticulum in renal proximal tubule cells of the straight (S3) segments. This ultrastructural effect was associated with a pronounced induction of the microsomal enzymes glucuronyl transferase and benzopyrene hydroxylase which persisted for at least 16 days after treatment. Renal dissection studies disclosed that the activities of these enzymes in 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated animals were not uniformly distributed within the kidney but followed the general known distribution of S3 cells. Enzyme activities were highest in the outer stripe of the medulla and cortex and lowest in the medulla. These studies demonstrate that the kidney does possess inducible microsomal enzyme systems, capabilities of which have not been appreciated previously due to the lack of a suitable inducing agent and their apparent concentration in a relatively small population of proximal tubule cells.