Gluconeogenesis from ¹⁴C- and ³H-Labeled Substrates in Normal and Cortisone-Treated Rats

Treatment of rats for 4 days with cortisone acetate (20 mg/day) was followed by intraperitoneal injection in trace amount of one of the following pairs of compounds: DL-alanine- 2-¹⁴C, DL-lactic acid-2-³H; DL-malic acid-3-¹⁴C, DL-malic acid-2-³H; succinic acid-2,2′-¹⁴C, succinic acid-2,2′-³H; or glycerol-l,3-¹⁴C, glycerol- 2-³H. Conversion of radioactivity to CO₂, blood glucose and liver glycogen was studied. With all ¹⁴C-labeled substrates there was an increase of ¹⁴C CO₂ after cortisone, which was partly due to an increased specific activity and partly to a general increase of respiration. Incorporation of ¹⁴C from alanine and malate into blood glucose was increased about 2-fold after cortisone, and there was no change in ¹⁴C from succinate or glycerol. Incorporation of tritium from lactate and malate into glucose was increased 4-fold and 5-fold, respectively, after cortisone, but there was no change in the amount of ³H transferred to glucose from succinate or glycerol. Tracer incorporation into glycogen was increased markedly from alanine- ¹⁴C, malate-¹⁴C, lactate-³H and malate-³H, less markedly from succinate-¹⁴C and glycerol-¹⁴C, and there was no significant change with succinate- ³H or glycerol-³H. Though not increased by cortisone, the conversion of ³H to glucose and glycogen from succinate or glycerol was basically higher than from lactate or malate. (Endocrinology78: 765,1966)