In vitro studies of DDT,DDE, and ATPase as related to avian eggshell thinning

Interspecific and inter-tissue differences were found in thein vitro sensitivity of oligomycin sensitive Mg²⁺ATPase (O.S.-ATPase) from avian mitochondrial homogenates to DDE. The enzyme from the target tissue, the shell gland of kestrels, which lay thin-shelled eggs on exposure to DDE, showed significantly greater sensitivity to DDE than O.S.-ATPase in muscle and brain preparations. The O.S.-ATPase from chicken shell gland was about nine times less sensitive than that from the kestrel. DDT, in contrast to DDE, was highly effective on O.S.-ATPase in all tissues tested from the three species of birds. In contrast to the high sensitivity of O.S.-ATPase, O.Ins.-ATPase and Na⁺-K⁺ATPase were not significantly affected by DDE or DDT. In addition, Ca²⁺-ATPases from mitochondrial and microsomal preparations from shell gland of kestrels were only minimally affected by DDT and DDE at concentrations over 20 times greater than those which inhibited O.S.-ATPase. The selectivity of DDE action in the eggshell thinning of kestrel is correlated with its action on shell gland O.S.-ATPases. However, because DDT effectively inhibits O.S.-ATPase from all tissues studied a combined effect is possible. Both would cause a reduction in ATP synthesis affecting energy-linked calcium transport. The need forin vivo studies including mitochondrial calcium transport is emphasized.Paper No. 11877, Scientific Journal Series, Minnesota Agricultural Experiment Station, University of Minnesota, St. Paul, MN 55108