HISTOCHEMICAL AND CYTOCHEMICAL LOCALIZATION OF THE EFFECTS OF JELLYFISH TOXIN (STOMOLOPHUS MELEAGRIS) ON RAT HEART TISSUE AND ITS ADENOSINE TRIPHOSPHATASE ACTIVITIES

The effect of Stomolophus meleagris toxin was tested on both intact rat cardiac tissue (either receiving an initial fixation with glutaraldehyde or fresh tissue) and a homogenate of rat cardiac tissue. Stomolophus toxin appeared to have a stimulatory effect on ATPase activity associated with plasma membranes in rat heart tissue initially fixed with glutaraldehyde. This correlated well with the fact that S. meleagris toxin is known to contain stimulatory components for Na('+),K('+) ATPase. However, complete loss of enzymatic activities was observed in tissue initially fixed with glutaraldehyde contaminated with 235 nm-absorbing polymeric component(s).; Low levels of S. meleagris toxin appeared to stimulate mitochondrial (Mito.) Mg('2+) ATPase activity found in both glutaraldehyde-fixed or fresh rat cardiac tissue, while high doses (or longer times of exposure) led to lysis of mitochondria. This biphasic type of response corresponded closely to that observed in Mito. Mg('2+) ATPase activity found in a rat heart homogenate exposed to increasing amounts of toxin (i.e., stimulation was observed at low toxin concentrations but inhibition at high toxin levels). Several hypotheses were offered in an attempt to explain these in vitro effects. Proteases known to be present from previous studies are suggested to account for ultrastructural changes observed in mitochondria in addition to the biphasic response to Mito. Mg('2+) ATPase to added toxin.; Mitochondrial Mg('2+) ATPase activity in rat heart homogenates was stimulated at low ( 0.5 mg) toxin levels. A similar biphasic response was observed in pre-incubation studies with 100 and 1000 (mu)g toxin, respectively. The oligomycin concentration (ca. 10('-5) M) required to elicit maximal inhibition in this Mito. Mg('2+) ATPase preparation agreed closely with reported literature values. In the presence of varying amounts of oligomycin, addition of 50 (mu)g toxin had little effect on the resultant ATPase activity (LD(,50) remained at 10('-7) M oligomycin); whereas, the addition of 500 (mu)g toxin increased the overall inhibition by 10-20%, with the ID(,50) of this system being 5 x 10('-8) M oligomycin. However, very little Na('+),K('+) ATPase activity was observed in any of the rat heart homogenate fractions.