An in vitro model to evaluate the effect of an organophosphoric agropesticide on cell proliferation in mouse seminiferous tubules

Recently, there has been public concern about the toxic effects of organoph osphoric pesticides (OP) upon human and animal populations. Since the semin iferous epithelium is an actively proliferating tissue, it was of interest to study germ cell proliferation in the isolated seminiferous tubules of mi ce that were cultured in the presence of Parathion(R) or paraoxon, its meta bolite. Eighteen 3-month-old CF-1 male mice were used. Paraoxon (PO) and Pa rathion(R) (PT) were added to cultures of seminiferous tubules in the follo wing groups: (1) Ham F-10 medium pH 7.4 (M) (control); groups 2 to 5, M+ de creasing doses of either PO or PT (0.8; 0.4; 0.04; 0.004; 0.0004 mM). Each group consisted of six mice. Incubation of the tubules was carried out for 5 h at 35 degrees C, 5%CO2, 95% air. One hour before the end of incubation 5 mu Ci of SH-thymidine was added to the cultures. DNA uptake was measured by scintillation counting. PO and PT at concentrations of 0.8 mM elicited a sharp decrease in testicular DIVA synthesis. Recuperation at concentration s under 0.4 mM was different. With PO it was rapid, possibly due to the hig h detoxificative ability of the testis, which contains high quantities of t he enzyme 'type A esterases' that hydrolyses PO. At concentrations lower th an PO, PT has an inhibitory effect upon germ cell proliferation, which dese rves further research.