Chronic Exposure to Paraquat Alters Spermatogenesis and Nuclear DNA Integrity of Epididymal Sperm in Mice

Abstract

Experimental evidence suggests that unintentional exposure to environmental chemicals may alter reproductive capability of males. The aim of the present study was to investigate effects of low concentrations of Paraquat (1,1'-dimethyl l-4,4'-brpyridinium), a commonly usecl broad-spectntm weedicide in Sri Lanka, on spermatogenesis of mice. Sexually mature mice were treated with 4 doses (7 , z, 4 and g mg &g body weight) of paraquat (n= I 0 / group) and the vehicle (distilled water: n = l0). Each dosage (in 0. t mt; was injected into the scrotal sac every other day for 7 days. Testicular spemn count and histological studies fdiameter of seminiferous tubule (width), thickness of the tubules, number of cyclesl were determined on post treatment day 7. Nuclear integrity of sperm DNA and abnormalities in sperm morphol ogy (using separate sperm smears) were determined. Treated mice showed a significant (p<0'05) increase in sperm abnormalities (for 1,2 and 4 mg/kgdoses) and nuclear integrity of sperm DNA in caput, corpus and cauda sperm of the epididymis. Results revealed disrup- tion of spermatogenesis process in all treated groups. Sp"r.n abnormalities were mainly concentrated on the sperm head. In addition, a significant (p<0.05) increase in tubular diam eter and a significant (p<0.05) reduction in Sertoli cell number and in round and elongatecl spermatids were observed in all treated groups. Earlier stlldies have shown that Ethylene GlycolMonomethyl Ether and its by products cause severe damages in the spermatogenesis in rat' This study suggests whether effects of Paraquat are mediated through Jamaged Sertoli cells' But a conclusion cannot be drawn from the present findings alone. HoweveE it is possible that tiee radical forrnation can interfere with integrity of Sertoli cells and sperrna togenesis. Further experiments are needed to conclude the mechanism of action of paraquart on epididymal sperm DNA.