Unchanged glycolytic capacity in rat kidney under conditions of stimulated gluconeogenesis. Determination of phosphofructokinase and pyruvate kinase in microdissected nephron segments of fasted and acidotic animals.

The glycolytic capacity in rat kidney was studied under conditions of stimulated gluconeogenesis like 48 h starvation and 48 h acidosis induced by force-feeding with a NH4Cl/glucose solution. Rats fed ad libitum and force-fed with a glucose solution served as controls. The specific activities of the key enzymes phosphofructokinase and pyruvate kinase were determined in single segments of the nephron. The determinations were performed by microdissection of lyophilized tissue sections followed by enzymatic analysis, including oil well technique, enzymatic amplification, and fluorometric measurement. In the distal portion of the nephron of both fed and force-fed animals a 10-fold higher specific activity of phosphofructokinase and pyruvate kinase was found compared with the proximal portion, known as the site of renal gluconeogenesis. Starvation and acidosis altered neither the distribution pattern nor the specific activities of these enzymes. From these results it is concluded that renal glycolysis does not undergo alterations at the level of enzymatic activities in favour of renal gluconeogenesis, probably because of the separate localization of both pathways within the nephron.