[The lysosomal proteolytic system and thyroid functional activity in rats administered chloroquine]

A 7-, 14-, and 21-day course of injections of the lysosomotropic drug chloroquine in a dose of 50-mg/kg per day causes a more than two-fold decrease of T3 concentration and insignificant changes in the level of T4 and thyrotropin in the blood serum of rats. In the series with 14- and 21-day courses of chloroquine injections, inhibition of the thiol cathepsins B and L with simultaneous activation of the aspartic proteinase cathepsin D occurred. Permeability of the lysosomal membranes for all hydrolases under study considerably increased after a 7-day course of chloroquine but reduced subsequently to the control level in longer treatment. The possible mechanisms of changes in the spectrum of lysosomal proteinases and functional activity of the thyroid are discussed.