Role of Ca++, CaATPase and alkaline protease in cardiac contraction band formation.

Cardiac cells' total homogenates and subcellular components Ca++, CaATPase and alkaline protease levels were matched with their respective microscopic samples in order to ascertain their role in the formation of contraction bands. It was seen that those samples having contraction bands also had a high incidence of intracellular Ca++, low CaATPase and high alkaline protease levels. This study confirms reports that contraction bands are not limited to pathological hearts (Adomian et al., 1977), but neither are they limited to artifacts related to autopsy procedures. They were seen in varying degrees of severity in hearts of healthy rats sacrificed by decapitation and less frequently with only sarcomeric involvement to absence of in animals sacrificed by diethyl ether overdose. It is postulated that the elevated Ca++ activated alkaline protease (pH 8.5) by inhibiting its inhibitor (Waxman and Krebs, 1978). It may have inhibited total CaATPase activity (Hasselbach, 1974) as well. We believe that the activated alkaline protease produced irreversible contraction bands by lysing the microhinge between light and heavy meromyosin.