Reduced calcium sensitivity of the sodium channel and the Na+/Ca2+ exchange system in the Kdr-type, DDT and pyrethroid resistant German cockroach, Blattella germanica.

To understand the biochemical cause of nerve insensitivity to DDT and pyrethroids two cation regulating systems, the Na+/Ca2+ exchange and the Na+ channel in the membrane preparation from the central nervous system of susceptible and resistant strains of the German cockroach were examined. Both systems from resistant insects have lower affinities to Ca2+ than those from their susceptible counterparts. The resistant strains show a prominent cross-resistance to all agents affecting calcium regulation (particularly A23187) and Na+ channel operations in vivo, indicating that the basic cause of the reduced nerve insensitivity in resistant insects is related to the reduction in calcium sensitivity in these systems.