[Histochemical study of the effect of phosphoroorganic esters Z-50 (fenchlorfos) and Z-51 (bromophos) on cholinesteras activity in the course of the muscle phase in experimental trichinellosis in mice].

The studies were carried out on mice between the 14th and 19th days, i.e., in the period of maximum penetration of T. spiralis larvae in the host's muscles. Phosphoro-organic esters were given orally to experimental animals in oil solution, at the following doses: Z-50 -- 150 mg per kg of body weight and Z-51 -- 100 mg per kg of body weight. The influence of esters on the activity of cholinesterases was investigated with the Koelle-Friedenwald method, modified by Gomori. The aim of the study was to establish the joint activity of the migrating Trichinella larvae and phosphoro-organic esters on the organism of the host. Z-50 and Z-51 penetrate in therapeutic doses the striated muscles rather weakly. 24 hrs after these compounds were given, acetylcholinesterase (AChE) activity was inhibited in motor end-plates in about 30%, and in muscle fibres infected with T. spiralis larvae in about 60-70%. Pseudocholinesterase (PChE) activity was stronger inhibited than AChE. 24 hrs after applying Z-50 and Z-51 PChE was inhibited in about 90%. Of the two phosphoro-organic esters being examined Z-51 stronger inhibited the cholinesterases activity than Z-50. It was found that the efficiency of phosphoro-organic esters in the course of trichinellosis depends on its ability of infiltration into the host's muscles and on the degree of inhibition of the active cholinesterases in the motor end-plates. Attention was drawn to the fact that increased activity of cholinergic system is one of the main factors in the patholgenesis of the second phase of trichinellosis, i.e., the migration and penetration of the larvae in the muscular fibres of the host.