Hormonal regulation of malic enzyme and glucose-6-phosphate dehydrogenase in adult rat liver

1988 ◽  
Vol 16 (1) ◽  
pp. 33-34
Author(s):  
PARMJIT S. SOHAL ◽  
WILLIAM J. ROESLER ◽  
RAMJI L. KHANDELWAL ◽  
JOSEPH F. ANGEL
Keyword(s):  
Rat Liver ◽  
Malic Enzyme ◽  
Hormonal Regulation ◽  
Adult Rat ◽  
Glucose 6 Phosphate Dehydrogenase

Hormonal regulation of malic enzyme and glucose-6-phosphate dehydrogenase in brown adipose tissue

1993 ◽  
Vol 264 (6) ◽  
pp. E874-E881 ◽  
Author(s):  
S. D. Carvalho ◽  
N. Negrao ◽  
A. C. Bianco
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Malic Enzyme ◽  
Hormonal Regulation ◽  
Inhibitory Effect ◽  
Thyroid Status ◽  
Brown Adipose ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Dose Dependent ◽  
Intact Rats

The activities of malic enzyme (ME) and glucose-6-phosphate dehydrogenase (G-6-PDH), two NADPH-generating lipogenic enzymes, were measured in brown adipose tissue (BAT) of rats undergoing various neurohormonal manipulations. Methimazole-induced hypothyroidism doubled the activity of these two enzymes but, surprisingly, triiodothyronine (T3) given to hypothyroid rats caused a time- and dose-dependent stimulation of up to three- to fourfold. Unilateral BAT denervation modestly reduced the activity of these enzymes (approximately 30%) and failed to prevent the stimulation induced by hypothyroidism, whereas growth hormone (GH) successfully blocked this effect of hypothyroidism. Insulin stimulated both enzymes regardless of the thyroid status but failed to abolish the inhibitory effect of GH. In intact rats, cold exposure caused a time-dependent increase in the activity of both ME and G-6-PDH, which reached 5.2- and 3-fold, respectively, after 96 h. This cold-induced stimulation was not observed in hypothyroid rats, but it was restored by physiological doses of thyroxine (800 ng.100 g body wt-1.24 h-1). Replacement with T3 (300 ng.100 g body wt-1.24 h-1), in contrast, did not have this effect. In hypothyroid rats with hemidenervation of BAT, norepinephrine (NE) modestly increased ME and G-6-PDH activities in the denervated side, with little or no effect in the intact side. Receptor-saturating doses of T3 (50 micrograms.100 g body wt-1.day-1 over 48 h) stimulated two- and threefold both enzymes in both sides, reducing or obliterating the effect of denervation. The data suggest a complex neurohormonal regulation of the activity of ME and G-6-PDH in BAT.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals 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

1985 ◽  
Vol 226 (1) ◽  
pp. 123-130 ◽  
Author(s):  
D J Stumpo ◽  
R F Kletzien
Keyword(s):  
Hormonal Regulation ◽  
Relative Rate ◽  
Primary Cultures ◽  
Fold Increase ◽  
Defined Medium ◽  
Enzyme Synthesis ◽  
Translation System ◽  
Adult Rat ◽  
Free Translation ◽  
Glucose 6 Phosphate Dehydrogenase

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.

Immunoquantitation of liver glucose-6-phosphate dehydrogenase and malic enzyme in normally and prematurely weaned rats

1983 ◽  
Vol 61 (10) ◽  
pp. 1108-1113 ◽  
Author(s):  
Donald W. Back ◽  
Joseph F. Angel
Keyword(s):  
Rat Liver ◽  
Malic Enzyme ◽  
Rabbit Serum ◽  
Enzyme Protein ◽  
Serum Antibodies ◽  
Infant Rats ◽  
Highly Correlated ◽  
Glucose 6 Phosphate Dehydrogenase

Rat liver glucose-6-phosphate dehydrogenase and malic enzyme were purified and rabbit serum antibodies were prepared against each enzyme. The activities and quantities of both enzymes in the livers of infant rats were subsequently determined during the weaning period. Glucose-6-phosphate dehydrogenase was present and active in the liver of spontaneously weaned rats on postnatal day 17 and increased from postnatal day 21 onwards. Malic enzyme and its activity were undetectable on postnatal day 17. The latter enzyme was detected on postnatal day 21 and increased rapidly afterwards. These changes occurred sooner and were more pronounced when the rats were weaned prematurely on postnatal day 17, especially when the diet contained sucrose. The activities of both enzymes were highly correlated with the amounts of enzyme protein present throughout the experiment. It appeared that the activities of both enzymes in infant rats were likely to be regulated by altering their synthesis and (or) degradation, rather than by activation of existing proteins, assuming that the latter can be detected by the antibodies employed.

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