Human Placental Ca2+-ATPases: Targets for Organochlorine Pesticides?

Millions of tons of p,p’-DDT and other organochlorine (OC) pesticides have been used worldwide in the past thirty years. Although the use of certain OC pesticides has been discontinued in several countries including the United States, they are still the pesticides of choice in developing countries. It is noteworthy that the recognized deleterious effects of OC pesticides on human health will NOT disappear due to this ban, since, for example, DDT residues in the ecosystem are expected to linger well beyond the beginning of the next century (Matsumura, 1975). OC pesticides are highly lipophilic compounds and are avidly stored in internal tissues, notably the fat depots. Several epidemiological surveys have documented a positive correlation between the amount of OC residues in maternal or cord blood, placenta, and fetal tissues and an increased incidence of spontaneous abortion (O’Leary et al., 1970a; Saxena et al., 1980), missed abortion (Bercovici et al., 1983), fetal prematurity (O’Leary et al., 1970b, 1972; D’Ecrole et al., 1976; Saxena et al., 1980) induction of early labor (Polishuk et al., 1977; Saxena et al., 1980, 1981), premature delivery, (Wassermann et al., 1982; Siddiqui and Saxena, 1985) or stillbirths (Curley et al., 1969; Saxena et al., 1983; Siddiqui and Saxena, 1985). Many forms of covert toxicity of OC pesticides which often times are expressed later in life (morphological, physiological, or neuro-behavioral) are suspected in surviving babies but this documentation is lacking at present. However, a significant increase in neonatal mortality has been well documented in rats (Fitzhugh and Nelson, 1947; Clement and Okey, 1974). Persistent stimulatory and behavioral effects are also known to occur in rats following prenatal exposure to dieldrin (Olsen et al., 1980). Although several hypotheses have been put forth, the underlying biochemical mechanism(s) responsible for these undesirable reproductive effects has not yet been established.