DIFFERENTIAL TIME-COURSE OF LIVER AND KIDNEY GLUCOSE-6 PHOSPHATASE-ACTIVITY DURING FASTING IN RATS

We have studied the time course of hepatic and renal microsomal glucose-6 phosphatase (Glc-6Pase) during long-term fasting in the rat, Liver microsomal Glc-6Pase increases up to 48 hr and significantly decreases after 48 hr of fasting. The following activities were determined at 0, 24, 48, 72 and 96 hr: 0.31+/-0.02; 0.50+/-0.82; 0.54+/-0.03; 0.44+/-0.03; 0.44+/-0.01 pmol min(-1) mg protein(-1), respectively (all values are means+/-SEM, n = 6). Concomitantly, kidney microsomal Glc-6Pase progressively increases throughout the fast (V-m = 0.21+/-0.01; 0.26+/-0.004; 0.30+/-0.01; 0.37+/-0.02; 0.40+/-0.01 mu mol min(-1) mg protein(-1), from 0 to 96 hr, respectively). These data suggest that the differential expression of Glc-6Pase activity in the liver and the kidney during long-term fasting could have an important role in the shift from a principally hepatic gluconeogenesis to a hepatic and renal gluconeogenesis.