The effect of some organophosphorous and organochlorine compounds on calcium uptake by Sarcoplasmic reticulum isolated from insect and crustacean skeletal muscle

Summary Relatively pure mitochondrial-free Sarcoplasmic reticulum (SR) was isolated from crab and cockroach skeletal muscle, and the SR calcium uptake was studied in control and insecticide-treated conditions by incubation in Ca⁴⁵ media followed by millipore filtration and counting by liquid scintillation methods. All insecticides used (parathion, DDT, BHC and tri-cresyl phosphate) at 1 mM concentrations caused a slight fall in the intrinsic Ca²⁺ content of the SR, but this Ca²⁺ loss was insufficient to explain the contracture induction effect of these agents.All insecticides used (at 1 mM) caused a massive inhibition of SR Ca²⁺ uptake, and all were able to release Ca²⁺ previously bound to the SR during incubation in the presence of ATP. It is concluded that the contracture-induction effect of these insecticides is due to their inhibition of SR Ca²⁺ uptake, resulting in a massive rise in myoplasmic free Ca²⁺.