The effect of ethanol, alone and in combination with the glucocorticoids and insulin, on glucose-6-phosphate dehydrogenase synthesis and mRNA in primary cultures of hepatocytes

Abstract

The hormonal regulation of the relative rate of synthesis and mRNA of glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) was studied in primary cultures of adult-rat liver parenchymal cells maintained in a chemically defined medium. Maintenance of hepatocytes from starved animals in a culture medium devoid of any hormones resulted in a 4-fold increase in the relative rate of G6PDH synthesis in 48 h. Parallel cultures treated with glucocorticoids alone exhibited a rate of G6PDH synthesis comparable with that in the control cultures, whereas insulin alone caused a 6.5-fold increase in the rate of synthesis in 48 h. However, if the cultures were treated with glucocorticoids and insulin simultaneously, a 13-fold increase in the rate of synthesis was observed. The effect of ethanol, alone and in combination with the hormones, on the relative rate of G6PDH synthesis was studied also. Ethanol alone caused an 8-fold increase in the rate of synthesis in 48 h, whereas the combination of ethanol, glucocorticoid and insulin caused a 25-fold increase. The amount of functional mRNA encoding G6PDH, as measured in a cell-free translation system, was compared with enzyme activity and relative rate of enzyme synthesis. The increases in G6PDH activity and relative rate of synthesis in primary cultures of hepatocytes treated with ethanol, alone and in combination with the glucocorticoids and insulin, were paralleled by comparable increases in G6PDH mRNA. The results of this study show that the glucocorticoids acted in a permissive manner to amplify the insulin stimulation of G6PDH synthesis and that insulin, glucocorticoids and ethanol interact to stimulate synthesis of G6PDH primarily by increasing the concentration of functional G6PDH mRNA.

Walker‐256 tumor growth causes oxidative stress in rat brain

“…Hormones and cytokines, such as glucocorticoids, TNF‐α and IL‐1, which are increased in plasma of tumor patients, regulate the activity of reducing power generating sites as CS and G6PDH (Stumpo and Kletzien 1985; Rosa et al . 1992; Leff et al .…”

Glucose‐6‐phosphate dehydrogenase: a “housekeeping” enzyme subject to tissue‐specific regulation by hormones, nutrients, and oxidant stress

“…For example, oxygen-derived free radicals have been implicated in the pathogenesis of ethanol-induced liver injury (50) and acute ethanol intoxication has been shown to stimulate superoxide anion production in perfused rat liver in situ (51). Earlier studies have demonstrated that ethanol is capable of inducing G6PDH activity, relative rate of G6PDH enzyme synthesis, and mRNA in primary cultures of rat hepatocytes (52). Further studies have shown that acetaldehyde is a likely metabolite mediating the effect of ethanol, with increases in G6PDH mRNA being observed within three hours of incubation (53).…”

Regulation and properties of glucose-6-phosphate dehydrogenase: A review

“…Hepatic G6PD is induced by chemicals such as diquat (Cramer et al, 1993), ethanol (Stumpo and Kletzien, 1985). Studies have revealed that ethanol induces G6PD activity, relative rate of G6PD enzyme synthesis and mRNA in primary cultures of rat hepatocytes (Stumpo and Kletzien, 1985).…”

“…Hepatic G6PD is induced by chemicals such as diquat (Cramer et al, 1993), ethanol (Stumpo and Kletzien, 1985). Studies have revealed that ethanol induces G6PD activity, relative rate of G6PD enzyme synthesis and mRNA in primary cultures of rat hepatocytes (Stumpo and Kletzien, 1985). The oxidative stress experiments in Trypanosoma cruzi showed that metacyclic trypomastigotes and amastigotes have high G6PD activity (Igoillo-Esteve and Cazzulo, 2006).…”