Human placental Ca2+-ATPase: in vitro inhibition by DDT homologs

Abstract

In vitro inhibition of Ca2+-ATPase by DDT homologs was studied using maternal brush-border membranes from human term placentas as an enzyme source. At 10 [mu]M concentration many of the compounds tested inhibited this enzyme. The order of effectiveness of inhibition was as follows: p,p'-DDE>p,p'-DDD>p,p'-DDT> methoxychlor(mec). Both p,p'-DDOH and p,p'-DDA did not inhibit the placental Ca2+-ATPase. Assays using varying concentrations (0.3 [mu]M to 0.1 mM) of p,p'-DDT were also performed. The inhibition of human placental Ca2+-ATPase ranged from 12% for 0.3 [mu]M p,p p,p'-DDT to 69% for 30 [mu]M p,p'-DDT. Higher concentrations of this pesticide failed to cause further enzyme inhibition.