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Plasma Corticosterone Levels and Hepatic Glycogen Metabolism in Young and Old Rats Fed Diets Devoid of an Essential Amino Acid¹

School of Public Health, University of California Los Angeles, California 90024

Plasma corticosterone and hepatic glycogen values were investigated in rats force-fed diets devoid of a single essential amino acid. Rats weighing 100, 200 or 500 g were fed —Thr, —Leu, —Met or a complete diet for 3 days. In most treatments the plasma corticosterone values were significantly less than controls in each group of rats fed a diet devoid of an essential amino acid. These data indicate that corticosteroid production may be impeded in rats fed diets devoid of an essential amino acid. The hepatic glycogen concentrations were significantly greater than the controls in the rats weighing 200 and 500 g fed the —Leu diet. In another study, the plasma corticosterone levels of rats fed four meals of the —Thr diet were less than the controls at 9, 12 and 15 hours postprandial. No significant differences were observed in plasma corticosterone levels in rats given the —Leu diet. At 9, 12, and 15 hours postprandial the hepatic glycogen concentrations of the rats fed the —Leu diet tended to be higher than control values. The hepatic glycogen values depleted more slowly at 12 and 15 hours postprandial. This finding was thought to be indicative of impaired hepatic glycogenolysis in the animals given the —Leu diet; however, an assay of hepatic phosphorylase a activity in rats fed a —Leu diet failed to demonstrate any differences from control values. The hepatic glycogen levels in rats fed the —Thr diet were higher than the controls at each time period although the differences were not significant. A study was conducted to determine if increased glycogenesis via a glucogenic amino acid was occurring in rats given the —Leu diet. Rats were injected with 5 µCi of ¹⁴C-valine. The ¹⁴C incorporation into glycogen tended to be higher in rats given the —Leu diet than those given the control diet, indicating that some increase in gluconeogenesis was occurring.

KEY WORDS: • corticosterone • glycogen • amino acid

¹ Supported in part by the Nutrition Foundation.

Manuscript received 30 July 1971.