A sensitive and specific radioimmunoassay for human ligandin has been developed and used to study ligandin release into the serum in acute and chronic hepatitis. Serum ligandin concentrations were elevated in 67 of 68 cases of acute viral hepatitis. Ligandin levels frequently returned to normal within the first 2 weeks of illness. The rapid disappearance of ligandin preceded the return to normal of serum SGOT. In chronic active hepatitis, serum ligandin levels correlated significantly (p < 0.01) with histologic severity of disease. This correlation was not seen with SGOT. Serum ligandin may be useful in monitoring progress and the need for therapy in chronic active hepatitis.
Ligandin, a basic protein (PI 8.9 to 9.3) found in abundance in mammalian liver, proximal renal tubules, and the small intestine, has been shown to have the enzymatic activity and the ability to bind nonsubstrate ligands, characteristic of glutathione S-transferase (GSH-T) (EC.2.5.1.18) (1). In the rat, this entity has been shown to consist of several different proteins (GSH-T AA, A, B, C, D, E, and M) with varying substrate specificities. GSH-T B is immunologically identical to ligandin (2). In man, there are three groups of GSH-T, of which the "cationic" GSH-Ts termed alpha, beta, gamma, delta, and epsilon are thought to be charge isomers of a single gene product, are immunologically identical, and are all called ligandin or ligandins (3).
In rats, the measurement of ligandin by radioimmunoassay (RIA) (4) has provided new information on its distribution on behavior in necrosis of the liver and proximal tubular cells of the kidney (5, 6 ) . Species specificity has precluded the use of the rat RIA in man. This paper describes purification of human liver ligandin, development of an RIA for human ligandin, and use of plasma ligandin measurements in the diagnosis of human liver disease.
Methods
Human liver tissue, obtained within 12 hr of death from patients in whom there was no evidence of previous liver disease, was removed onto dry ice and stored at -70ยฐC unless processed immediately.
ENZYME ACTIVITY
The formation of glutathione (BDH Chemicals, Poole Dorset, England), adducted with l-chloro-2,4-dinitroben-