Modulation of γ-glutamyltranspeptidase activity in rat liver plasma membranes by thyroid hormone

Sulakhe, Susan J.; Tran, Sam T.; Pulga, Vivian B.

doi:10.1016/0020-711x(90)90206-i

Cited by 22 publications

(9 citation statements)

References 30 publications

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“…In terms of hormones, glucocorticoids have been shown to effect a low level increase in enzyme activity 49,50 while our studies have shown that T 3 exerts a rapid decrease in GT activity in the liver. 51 We have also observed sex-dependent differences in the activity of GT in the liver of the adult, with activity in the female being $ three-fold higher than activity in the male. 19 The flax-induced increase in GT, therefore, is of the same order of magnitude as other normal regulatory changes in activity of this liver enzyme.…”

mentioning

confidence: 83%

The effects of dietary flaxseed on the Fischer 344 rat: I. Development, behaviour, toxicity and the activity of liver γ‐glutamyltranspeptidase

Hemmings

Barker

2003

Cell Biochemistry & Function

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The effect of exposure to, followed by consumption of, 10% flax chow from the 18th day of gestation to the 86th day after birth was examined in male and female Fischer 344 rats. Growth curves of the flax chow-fed rats were identical to those of regular chow-fed rats, as were such developmental milestones as pinna development, growth of hair and eye opening. Acoustical startle and the righting reflexes, developmental behavioural indices, were also the same. Blood glucose levels were comparable in flax chow-fed and regular chow-fed rats at all stages of development, indicating that flax is without effect on glucose balance. There were no signs of toxicity in the flax chow-fed rats since their plasma levels of alanine aminotransferase and gamma-glutamyltranspeptidase (gammaGT) were the same as those of regular chow-fed rats. The activity of gammaGT displayed an increase in the livers of flax chow-fed rats after puberty, more so in the male-four-fold-than in the female-1.38-fold. This is suggestive of an estrogenic effect which implicates an effect of an estrogenic flax lignan. An hepatobeneficial effect of the flax-induced increase in liver gammaGT is discussed. In summary, dietary 10% flax chow is without long-term effect on growth, development and behaviour, is non-toxic and may be hepatoprotective.

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confidence: 83%

The effects of dietary flaxseed on the Fischer 344 rat: I. Development, behaviour, toxicity and the activity of liver γ‐glutamyltranspeptidase

Hemmings

Barker

2003

Cell Biochemistry & Function

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“…Other studies have noted increases in GGT activity in liver and plasma of STZ-induced diabetic rats (12)(13)(14). Enzyme expression was once thought to be under control of thyroid hormone; however, administration of thyroid hormone did not restore GGT activity to normal in diabetic rat liver (15). These studies demonstrated reversal of activity with insulin injections; however, the decrease in plasma membrane activity was accompanied by an increase of GGT activity in serum.…”

Section: Introductionmentioning

confidence: 90%

Streptozotocin-induced diabetes increases?-glutamyltranspeptidase activity but not expression in rat liver

Watkins

Klaunig

Smith

et al. 1998

J. Biochem. Mol. Toxicol.

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“…In liver, previous studies including our own have established that -glutamyltranspeptidase is a plasma membrane-bound enzyme although there may be a small amount that is soluble. [9][10][11] To achieve these objectives, we studied the effect of flaxseed consumption on the liver of the Fischer 344 rat. To differentiate between effects produced by the oil or the lignan components of flax, we used 10% flax diets as we have done before and two different flax strains that were comparable in the lignan component but differed substantially in the oil component: a strain high in SDG lignan (1.5% SDG as % oil free flaxseed) and high in ALA (60% total fatty acids); and a strain, high in SDG lignan (1.5% SDG as % oil free flaxseed) but low ALA (2.2% ALA).…”

Section: Introductionmentioning

confidence: 99%

The effects of dietary flaxseed on the Fischer 344 rat: II. liver γ‐glutamyltranspeptidase activity

Hemmings¹,

Westcott²,

Muir³

et al. 2004

Cell Biochemistry & Function

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The effect of 10% flax chow consumption from the 30th to the 130th day after birth was examined in male Fischer 344 rats. The effects of both the high lignan/high oil Norlin strain and a high lignan/low oil Solin strain of flaxseed were compared. Physically and behaviourally there were no differences in rats belonging to the three dietary groups at any time. At 50 and 100 days of dietary exposure, blood glucose levels were the same in Norlin and Solin flax chow-fed and as well as regular chow-fed rats; there were no signs of toxicity in the Norlin and Solin flax-fed rats since their plasma levels of alanine aminotransferase were the same and equal to those of regular chow-fed rats. The activity of gamma-glutamyltranspeptidase (gammaGT) displayed an increase in the liver homogenates of flax chow-fed rats. This increase was the same in Norlin and Solin flax-fed rats at 50 and 100 days. Thus the liver effect was not oil, but lignan, likely secoisolariciresinol diglucoside (SDG), induced and was effected early on, and sustained, after flax exposure. The degree of heat activation of liver homogenate gammaGT was the same in regular chow-fed and flax chow-fed rats. Compared to liver homogenate gammaGT activity, the soluble form of gammaGT was expressed at very low levels while the plasma membrane-bound form of gammaGT was expressed at very high levels in rat liver in both regular chow-fed and flax chow-fed rats. There was no effect of flax feeding on the soluble form of liver gammaGT which was expressed at a very low level. Flax feeding effected an increase in the activity of gammaGT in isolated plasma membrane fractions which mirrored that in liver homogenates: the same degree of increase was seen in Norlin flax chow-fed and Solin flax chow-fed rats. Flax consumption effects an increase in the activity of liver gammaGT at the level of the plasma membrane which is lignan dependent, physiologically relevant and may be linked to hepatoprotection against injury through an increase in reduced glutathione.

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Modulation of γ-glutamyltranspeptidase activity in rat liver plasma membranes by thyroid hormone

Cited by 22 publications

References 30 publications

The effects of dietary flaxseed on the Fischer 344 rat: I. Development, behaviour, toxicity and the activity of liver γ‐glutamyltranspeptidase

The effects of dietary flaxseed on the Fischer 344 rat: I. Development, behaviour, toxicity and the activity of liver γ‐glutamyltranspeptidase

Streptozotocin-induced diabetes increases?-glutamyltranspeptidase activity but not expression in rat liver

The effects of dietary flaxseed on the Fischer 344 rat: II. liver γ‐glutamyltranspeptidase activity

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