Glucuronidation and sulfation in rabbit kidney.

Mammalian kidneys contain a heterogeneous population of cell types that perform a variety of diverse functions. The present study was undertaken to determine the relative intrarenal distribution of UDP-glucuronosyltransferase and sulfotransferase activities. Female rabbit kidneys were dissected, and homogenates of cortex, outer stripe of the medulla and proximal tubule segments were prepared. Proximal tubule segments, derived primarily from the S2 region of the tubule, were isolated using purely mechanical methods. UDP-Glucuronosyltransferase and sulfotransferase activities directed toward 1-naphthol were highest in proximal tubules (2.86 +/- 0.13 nmol and 133 +/- 13.1 pmol product formed/min/mg protein, respectively) compared to outer stripe (45% and 64% of proximal tubule activity, respectively) and cortex (61% and 45%, respectively). Detergent increased 1-naphthol glucuronidation in homogenates of cortex and medulla, but depressed activity in proximal tubules. Subcellular fractionation of proximal tubule cells by isopycnic and rate density centrifugation revealed that UDP-glucuronosyltransferase activity distributed with the denser components of the endoplasmic reticulum and/or Golgi. Moreover, although the majority of sulfotransferase activity distributed as free (cytosolic) protein, sulfotransferase activity was also observed in fractions containing denser components of the endoplasmic reticulum and Golgi. Proximal tubule segments also exhibited the highest specific activity of UDP-glucose dehydrogenase, the enzyme involved in UDP-glucuronic acid synthesis (1.5-fold higher in tubules than in other regions.(ABSTRACT TRUNCATED AT 250 WORDS)