The activity of γ-glutamyl transferase (γ-GT) in the liver of 36 chronic alcoholics was
twice as high as in the control group. The elevation was of the same order in cases with and
without hepatic lesions. However, the activity of γ-GT in the sera of alcoholic patients with
chronic hepatitis and liver cirrhosis was significantly higher than in the remaining alcoholics. There
was no correlation between the enzyme activities in the liver and in the serum of the patients
examined. Consequently, the determination of liver γ-GT activity bears no clinical significance in
chronic alcoholics.
Fluorescence microscopy in experimental hexachlorobenzene porphyria in rats has demonstrated porphyrin deposits in the epithelial cells of the proximal renal tubules and the loop of Henle. In the glomeruli, interstitium, distal tubules, and the collecting tubules, no porphyrins were detected. The similarity of this finding with the data on some forms of porphyrinuria and porphyria in man suggests that the proximal tubules and the loop of Henle play an important role in the mechanism of renal porphyrin excretion.
The mechanism responsible for the changes in serum and liver γ-glutamyl
transpeptidase (γ-GT) activity was studied in a model of experimental hexachlorobenzene
porphyria in rabbits. Porphyria followed the administration of hexachlorobenzene in
doses of 280 μmol • kg^-1 body weight, which were given daily through a gastric tube over
a 20-day period.
Serum γ-GT activity and the activities of the lysosomal enzymes β-N-acetylglucosaminidase
and α-mannosidase were increased, whereas L-aspartate: 2-oxoglutarate aminotransferase
and L-alanine: 2-oxoglutarate aminotransferase remained unaltered. There was
a considerable increase in liver microsomal protein, γ-GT, cytochrome P-450, anilinehydroxylase,
aminopyrine-demethylase and δ-aminolevulinic acid synthase. In the liver
γ-GT was detected in the microsomes as well as in the cytoplasm where enzymatic activity
was higher. The high correlation coefficient between liver γ-GT, cytochrome P-450 and δ-
aminolevulinic acid synthase witnesses a hexachlorobenzene-induced γ-GT formation in
the liver. A statistically significant correlation between serum and liver γ-GT activity was
also found. These data strongly suggest that the increase in serum γ-GT activity may
result from the induction of the enzyme in the liver.
Serum, liver and renal γ-glutamyl transpeptidase (GGT) activities were
studied in four groups of rabbits : controls, rabbits with obstructive extrahepatic cholestasis,
rabbits with obstructive anuria, and animals with combined obstructive extrahepatic
cholestasis and obstructive anuria. Serum GGT was essentially increased in rabbits with
obstructive extrahepatic cholestasis, showing peak values in the combined cholestasis +
obstructive anuria group, and practically normal values in animals with anuria. Liver
GGT was increased in both cholestasis groups, but the increase was less prominent than
the increase in serum GGT and there was no correlation between them.
In both anurie groups renal GGT was reduced, probably as a result of inhibited
enzyme synthesis secondary to the altered conditions for adequate renal function.
The results obtained are suggestive of a probable renal involvement in the formation
of the serum GGT activity level.
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