title: ATP- and calcium-controlled contraction in a saponin model of Physarum polycephalum.
abstract: Saponin models of the plasmodial strand of Physarum polycephalum were constructed to study how Ca2+ and ATP regulate the generation of tension. ATP-induced isometric tension in a saponin model increased with an increase in ATP concentration until maximum tension (0.3-1.7 mg) was reached at about 1 mM. The sensitivity of the model to ATP was heightened three to five times in a basic solution containing an ATP-regenerating system, the maximum tension (0.3-0.6 mg) being reached at 0.2 to 0.3 mM ATP. Contraction of the model also depended on the Ca2+ concentration irrespective of the presence or absence of the ATP-regenerating system. The optimal pCa was 7.0, and tension decreased with a Ca2+ concentration above or below this value. These results indicate that the tension generated in the plasmodial strand of Physarum in vivo may be regulated by ATP and/or Ca2+.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D007700:Kinetics; D008954:Models, Biological; D010804:Physarum / Q000187:drug effects / Q000502:physiology*; D012503:Saponins; D013314:Stress, Mechanical
chemical_list: D012503:Saponins; D000255:Adenosine Triphosphate