INTRODUCTION

Although DDT (1,1-dichlorodiphenyltrichloroethane), a well-known organochlorine pesticide, has not been used in North America since 1972, it is still being used in Mexico and therefore will continue to enter the environment through long-range transport. Its metabolite, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), persists in the environment and can be detected in the sera of >90% of the North American population. It is consistently found in follicular fluids and serum of women. In one of these studies in which 74 women provided samples, 97% of the sera and 95% of the follicular fluids contained detectable amounts of DDE. In women undergoing in vitro fertilization (IVF), there was a negative correlation between high levels of follicular fluid DDE and fertilization, with high levels of DDE associated with failed fertilization. Levels of DDE in follicular fluid range from 0.2 to 11.8 ^g/kg and were higher in cervical secretions (2-151 ^g/ kg). Recent data obtained from men from the Boston area show a general trend suggestive of an association between DDE and abnormal motility, concentration, and morphology of sperm, corroborating results from other studies with Mexican men.

There are several mechanisms by which DDE could be acting as an endocrine disruptor: through the steroidogenic pathway, through receptor-mediated changes in protein synthesis, as antiandrogens or estrogens, as inhibitors of synthesis of other hormones, and by altering the flux of ions across the membrane, as occurs in egg shells. DDE causes the thinning of egg shells in birds probably because of an inhibition of Ca2+-dependent adenosine triphosphatase, calcium binding protein, and carbonic anhydrase. DDT at concentrations of 64 and 128 ^M inhibited ATP-induced Ca2+ uptake in bovine oviductal cells. Calcium has been implicated in the mechanism of action of FSH in stimulating progesterone formation in rat and porcine granulosa cells, and hCG is a stimulator of Ca2+ uptake in human granulosa cells. The inhibitory effects of DDT on Ca2+ uptake in bovine oviductal cells and the effects of its metabolite DDE on thinning of egg shells led us to hypothesize that DDE inhibits Ca2+ uptake in human granulosa cells. The aim of this study was to determine whether DDE can alter intracellular Ca2+ concentrations in human granulosa cells and affect the Ca2+ response to FSH and hCG.