Segmental heterogeneity of enzymatic response during compensatory renal growth.
The activities of DNA polymerase alpha and key enzymes of gluconeogenesis and glycolysis were measured in different segments of the rat nephron at various times (up to 96 hrs) following a unilateral nephrectomy (UNx). Tubule fragments were obtained after collagenase treatment followed by centrifugation on a Percoll gradient. The DNA polymerase alpha activity in control rats showed moderate and similar values in different segmental extracts as well as in the whole kidney extract (1700-1800 mumumole [3H] dAMP/mg DNA). In UNx rats, activity in proximal tubules (PT) measured at 24, 48, 72 and 96 hrs after nephrectomy represented an increase of 60%, 200%, 420% and 370% respectively over control values. Distal tubule fragments (DT) showed only minor increases. The results demonstrate that the proximal tubule accounts for most of the compensatory renal growth (CRG) in the remaining kidney. The gluconeogenic and glycolytic enzymes were confined to the PT and those of glycolysis to the DT fragments. Following UNx, the specific activities of these enzymes were not modified in the remaining kidney; however, the overall activity of gluconeogenesis was increased as a result of the cell hyperplasia occurring in the PT. Our work also illustrates that biochemical studies of CRG on the whole organ may provide misleading information due to the presence of heterogenous cell populations in the mammalian kidney and to their uneven response in CRG.
D000818:Animals; D004257:DNA Polymerase II / Q000378:metabolism*; D005943:Gluconeogenesis; D006019:Glycolysis; D007668:Kidney / Q000254:growth & development*; D007686:Kidney Tubules, Distal / Q000201:enzymology; D007687:Kidney Tubules, Proximal / Q000201:enzymology; D007700:Kinetics; D008297:Male; D009392:Nephrectomy; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D004257:DNA Polymerase II; D010729:Phosphoenolpyruvate Carboxykinase (GTP)