Studies on the Mechanism of the Changes in Serum and Liver γ-Glutamyl Transpeptidase Activity. I. Experimental Extrahepatic Cholestasis in Rabbits

Abstract

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.

Clinical Biochemistry and Hematology

“…Polish rabbits are reported to have higher BUN levels than New Zealand White or Dutch Belted strains (Kozma et al, 1974). Some causes of elevated BUN include urolithiasis and obstruction of urine flow, or kidney tumors or ureteral ligation (Adjarov et al, 1976). Low BUN may be due to hepatic insufficiency or loss of muscle mass due to dental disease (Melillo, 2007).…”

Cortisol Regulation of Gamma-Glutamyl Transpeptidase in Liver, Choroid Plexus, Blood Plasma and Cerebrospinal Fluid of Developing Chick Embryo

“…Our previous paper [19] and this present observation indicate that the increased GGT activity in the blood plasma and CSF reflects accelerated differentiation and functional maturation connected with an increased enzyme synthesis in embryonic cells by the steroid hormone. However, the marked increase of GGT activity in blood plasma of 15-day-old chick embryos may combine de novo synthesis of enzyme protein with the solubilizing effect of cortisol-in duced cholestasis in bile ducts followed by an increased regurgitation of the bile enzyme to blood [1,7,12]. Nevertheless, the rapidity and extent to which soluble GGT activity in biological fluids may correlate with the corti sol-induced increase of membrane-bound GGT activity in brain, spinal cord, choroid plexus and liver require further investigation.…”

“…Gamma-glutamyl transpeptidase (GGT; gamma-glutamyl transferase, EC 2.3.2.2), a membrane-bound enzyme with a possible re lation to the transport of amino acids and peptides [21], has its soluble form present in blood plasma and in other body fluids [1,11] including cerebrospinal fluid (CSF) [33]. As the amount of soluble GGT in the cytosol of 1 A preliminary report of some of these findings was presented at the International Symposium Neuroontogeneticum Tertium, Prague, July 9-14, 1979. different animal cells is limited [6,25], the soluble activity of this enzyme in body fluids probably originates from cell membrane sur faces [12] where GGT is attached as an ectoenzyme.…”

“…As the amount of soluble GGT in the cytosol of 1 A preliminary report of some of these findings was presented at the International Symposium Neuroontogeneticum Tertium, Prague, July 9-14, 1979. different animal cells is limited [6,25], the soluble activity of this enzyme in body fluids probably originates from cell membrane sur faces [12] where GGT is attached as an ectoenzyme. While the soluble enzyme in blood plasma is mainly of hepatic origin [1,12], its presence in CSF might reflect not only a rapid turnover of the membrane surfaces of lining ependymal cells and choroid plexus epitheli um [2,18,34] which have a high activity of GGT, but also of naturally occurring cell loss in the embryonic brain and spinal cord [8,27], Because of the lack of data concerning the developmental formation and cortisol regula tion of GGT in liver, choroid plexus, blood plasma and CSF of chick embryo, it seemed to be of interest to describe the development al profile of the membrane-bound and solu ble form of GGT in the embryonic organs and body fluids. This may then point to a possible relationship of the soluble form of the en zyme with that which is bound to cell mem branes of embryonic organs and tissues, and might also reveal a regulatory effect of corti sol on these two forms of GGT in the embry onic chick.…”