Effects of cyclodiene compounds on calcium pump activity in rat brain and heart.

The in vitro and in vivo effects of aldrin, dieldrin, and endrin on calmodulin regulated Ca2+-pump activity in rat brain synaptosomes and heart sarcoplasmic reticulum were investigated. All the 3 cyclodiene compounds inhibited both brain synaptosomal and heart sarcoplasmic reticulum Ca2+-pump activity in vitro in a concentration dependent manner. Calmodulin depleted Ca2+-pump activity was insensitive to the action of toxic compounds. Oral administration of pesticides (0.5-10 mg/kg) to rats similarly decreased the Ca2+-pump activity, in addition to decreasing the levels of calmodulin of both brain and heart thus indicating disruption in membrane Ca2+ transport mechanisms. Exogenous addition of calmodulin (1-20 micrograms) could effectively reverse the pesticide induced inhibition. Ca2+-pump activity is more sensitive to the 3 cyclodiene compounds in brain than in heart. The results of the present study indicate that the cyclodiene compounds may produce neurotoxic effects by altering calmodulin regulated calcium dependent events in neurons.