Dietary and hormonal regulation of some enzyme activities associated with gluconeogenesis in rabbit liver.
1. Starvation increases the activity of cytosolic P-enolpyruvate carboxkinase in rabbit liver some 4-5 fold but does not alter the activities of mitochondrial P-enolpyruvate carboxykinase, fructose-1,6-diphosphatase or glucose-6-phosphatase.2. Alloxan-induced diabetes increases the activities of cytosolic P-enolpyruvate carboxykinase, fructose-1,6-diphosphatase and glucose-6-phosphatase approx. 6-, 2- and 2-fold, respectively. Again the activity of mitochondrial P-enolpyruvate carboxykinase is not altered. 3. Administration of mannoheptulose rapidly increases blood glucose levels and also causes a significant increase in cytosolic P-enolpyruvate carboyxkinase activity within 4 h. The activities of mitochondrial P-enolpyruvate carboxykinase, fructose-1,6-diphosphatase and glucose-6-phosphatase are not affected. 4. Administration of hydrocortisone also increases blood glucose levels and the activities of cytosolic P-enolpyruvate carboxykinase and glucose-6-phosphatase are significantly increased within 12h. Again, mitochondrial P-enolpyruvate carboxykinase and fructose-1,6-diphosphatase activities remain unaffected. 5. The observations that (A) the activity of cytosolic P-enolpyruvate carboxykinase responds to more situations conducive to gluconeogenesis than do the activities of mitochondrial P-enolpyruvate carboxykinase, fructose-1,6-diphosphatase and glucose-6-phosphatase, and (B) cytosolic P-enolpyruvate carboxykinase activity is rapidly adaptive under appropriate circumstances, suggests that this particular enzyme's activity plays an important role in the regulation of gluconeogenesis in rabbits.
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D006597:Fructose-Bisphosphatase / Q000378:metabolism; D005943:Gluconeogenesis / Q000187:drug effects; D005952:Glucose-6-Phosphatase / Q000378:metabolism; D006854:Hydrocortisone / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008356:Mannoheptulose / Q000494:pharmacology; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000378:metabolism; D011817:Rabbits; D013217:Starvation
D001786:Blood Glucose; D008356:Mannoheptulose; D006597:Fructose-Bisphosphatase; D005952:Glucose-6-Phosphatase; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D006854:Hydrocortisone