Alterations in specific activity of glucose-6-phosphatase in laboratory rats after leptospiral exposure followed by triiodothyronine administration.

OBJECTIVE

To determine the effect of leptospirosis on thyroid hormone induction of the specific activity of hepatic microsomal glucose-6-phosphatase in laboratory rats.

ANIMALS

Male Fisher 344 rats, 6 and 24 months old, healthy and infected with leptospirosis.

PROCEDURE

The maximal velocity of glucose-6-phosphatase in intact and detergent-disrupted hepatic microsomes was assayed in duplicate or triplicate at 5 substrate concentrations, by monitoring the release of inorganic phosphate at 0-, 5-, and 10-minute intervals. The method of least squares was used to determine the velocity of the reactions. The level of statistical significance was determined, using the Student's t-test for unpaired data. Thyroid hormone (40 micrograms of T3/ 100 g of body weight) was administered for 5 consecutive days prior to sacrifice.

RESULTS

Leptospirosis significantly increased the specific activity of the translocase component of glucose-6-phosphatase in old, but not young, rats. The activity of the translocase increased more than three-fold in untreated, infected old animals, compared with untreated, healthy old animals. Thyroid hormone induced a two- and threefold increase in the specific activities of the translocase in young and old healthy animals, respectively. Thyroid hormone did not increase the activity of the translocase in old animals infected with leptospirosis.

CONCLUSIONS AND CLINICAL RELEVANCE

Leptospirosis alters the specific activity and induction by thyroid hormone of the translocase component of hepatic microsomal glucose-6-phosphatase in old male Fisher 344 rats. It is necessary to be aware of possible alterations in hepatic membrane-bound enzymes after leptospiral infection of older laboratory animals.