Elevation of plasma levels of lysosomal enzymes during treatment with rifampicin and isoniazid

The activities of the enzymes γ-glutamyl transpeptidase, β-glucuronidase, β- N-acetylglucosaminidase, and alanine transaminase were measured in the plasma of 24 patients receiving treatment for tuberculosis with rifampicin and isoniazid. Except for seven patients, five of whom were known to be high alcohol consumers, γ-glutamyl transpeptidase levels were normal and did not reflect the known inducing effects of rifampicin on liver cell microsomal enzymes. The predominantly lysosomal enzymes β-glucuronidase and β- N-acetylglucosaminidase were significantly raised compared to controls (p < 0.001), and there was a significant correlation between the two enzymes ( r = 0.661, p < 0.001). This elevation occurred within 4 weeks and was then independent of the duration of treatment. Alanine transaminase levels were normal, excluding any more general hepatocellular damage. These findings suggest an increase in lysosomal enzyme synthesis and release during rifampicin and isoniazid therapy.