The interrelationship of the concentration of hydrogen ions, bicarbonate ions, carbon dioxide and calcium ions in the regulation of renal gluconeogenesis in the rat

摘要

p1. The interrelationship of acidosis and Casup2+/supon the stimulation of gluconeogenesis by rat kidney-cortex slices was studied. 2. Casup2+/supstimulated gluconeogenesis from glutamine, glutamate, 2-oxoglutarate, succinate, malate, pyruvate, lactate and fructose, but not from galactose. 3. The [Casup2+/sup] needed for optimum gluconeogenesis was about 2mm, but at this concentration, acidosis, produced iin vitro/i by a decrease of [HCOsub3/subsup?/sup] in the medium at constant ip/iCOsub2/sub or by an increase in ip/iCOsub2/sub at constant [HCOsub3/subsup?/sup], did not stimulate gluconeogenesis. 4. In the absence of Casup2+/sup, acidosis (low [HCOsub3/subsup?/sup]) stimulated gluconeogenesis from glutamine, glutamate, 2-oxoglutarate, succinate, malate, pyruvate and lactate but not from fructose or galactose. With succinate as substrate, the stimulatory effect of acidosis (low [HCOsub3/subsup?/sup]) disappeared at Casup2+/supconcentrations above 1.0mm. 5. The [HCOsub3/subsup?/sup] was the most important determinant of the acidosis effect since a decrease of pH caused by an increase in ip/iCOsub2/sub did not uniformly stimulate gluconeogenesis, whereas a decrease in [HCOsub3/subsup?/sup] without a change in pH consistently stimulated glucose formation in a way similar to the stimulation produced by acidosis (low [HCOsub3/subsup?/sup]) in the absence of Casup2+/sup. 6. Acidosis iin vitro/i inhibited the rate of decrease of activity of phosphoenolpyruvate carboxylase in slices, and Casup2+/supcaused an increase in the activity of fructose 1-phosphate aldolase. 7. Respiratory acidosis iin vitro/i caused an increase in the activity of phosphoenolpyruvate carboxylase in kidney cortex and an increase in gluconeogenesis from glutamine. 8. Possible points of interaction between Casup2+/sup, Hsup+/supand HCOsub3/subsup?/supwith the gluconeogenic sequence are discussed./p