Ultrastructure of mouse teratozoospermia induced by parathion

Eduardo Bustos-Obregn, Octavio Daz

Biology of Reproduction Unit, Program of Morphology, ICBM, Faculty of Medicine, University of Chile.PO Box 70061, Santiago 7, Chile.

Asian J Androl  1999 Jun; 1: 37-43

Keywords: spermatozoa; organophosphorous compounds; parathion; pesticides

Male fertility has been correlated to sperm counts, motility and morphology^[1]. Wyrobek et al (1983)^[2], evaluating changes in sperm morphology caused by chemicals (including some pesticides) found that analysis of teratozoospermia is a useful tool to asses testicular toxicants.

In view of their wide agricultural use and scarce reproductive information available regarding organo-phosphoric agropesticides, the effect of parathion on mouse sperm morphology was studied.

Young adult CF-1 male mice (70-90 days old; mean weight 35 g) were intraperitoneally injected with a single dose of pure parathion (PP) (purchased from Sigma Co, USA) at a dose of 109 mg/kg body weight or commercial Parathion (PC), 3 mg/kg body weight. Both doses correspond to 1/3 the LD₅₀. Control mice were injected with the vehicle (0.85% NaCl). Groups of 5 animals were sacrificed at 1, 8, 40 and 50 days after injection. Epididymal spermatozoa were obtained and examinated by routine light (OM) and electron microscopy, both transmission (TEM) and scanning (SEM), to describe the main changes in sperm morphology. Teratozoospermia in OM was classified according to Vigil and Bustos-Obregn (1985)^[3] and was reported elsewhere^[4,5].

All treated animals have a significant decrease (P<0.01) of normal sperm with maximal teratozoospermia by 8 days post injection, without major differences between PP and PC. Flagellar anomalies were conspicuous in OM and reached maximal values by 50 days (62.5% for PP, P<0.01; 48.4% for PC, P<0.01). Head anomalies were found to be 3-fold of the control values (3.3%) at 8 and 40 days in the PP treated animals (P<0.05).

Because of the implicit relevance of head morphology for the sperm fertilizing ability the electron microscopical study reported here does not focus on flagellar alterations. 

One important morphogenetic factor involved in normal head shape is the degree of chromatin packing, which is known to be altered by Parathion^[6]. If head anomalies are detected at short time intervals in epididymal sperm (1 day), it implies damage to sperm nuclei of late elongated spermatids. If teratozoospermia persists for longer times (even over the duration of complete mouse spermatogenesis, which is 35 days), it means that through damage of Sertoli cells an altered relationship to the germ cells results in faulty spermatid differentiation. The affected germ cell can be determined according to the timing of the spermatogenic cycle in mouse^[7]. Such a situation is known to occur after exposure to Malathion^[8], another organophosphoric agropesticide.

The main head anomaly seen in TEM is bizarre deformation of the nucleus with lack of normal chromatin condensation. This trait is also seen in SEM as an irregular surface of the head area, that looks bumpy. Fragility of these abnormal heads is such that quite often they are disrupted when seen in SEM, while the flagellum of the same cell looks normal. In some cases, there is cytoplasmic droplet in the flagella, corresponding to a trait of immaturity both in treated and even in a few control cases.

A summary of the observations on sperm morphology is given in Table 1. The altered morphological sperm traits briefly reported here were observed at all time intervals after a single injection of parathion. Therefore, the toxic acts at different stages of spermatogenesis and seems also to affect Sertoli cell function. This is a long lasting effect and may cause male infertility, as has been reported for other plaguicides, known to represent a serious hazard for human reproductive health, such as dibromo-chloropropane^[9].

Table 1. Percentage of mouse sperm teratozoospermia 8, 40 and 50 days after a single injection of pure (PP) or commercial (PC) parathion. n=5. ^bP<0.05; ^cP<0.01 (Fisher test).

Acknowledgements