Changes in diadenosine tetraphosphate levels in Physarum polycephalum with different oxygen concentrations.
Cellular levels of diadenosine tetraphosphate (Ap4A) were measured, by a specific high-pressure liquid chromatography method, in microplasmodia of Physarum polycephalum subjected to different degrees of hypoxia, hyperoxia, and treatment with H2O2. Ap4A levels increased three- to sevenfold under anaerobic conditions, and the microplasmodia remained viable after such treatment. Elevated levels of Ap4A returned to the basal level within 5 to 10 min upon reoxygenation of the microplasmodia. The increases in Ap4A levels were larger in stationary-phase or starved microplasmodia than in fed, log-phase microplasmodia. The maximal increase measured in log-phase microplasmodia was twofold. No significant changes in Ap4A levels occurred in microplasmodia subjected to mild hypoxia, hyperoxia, or treatment with 1 mM H2O2. These results indicate that in P. polycephalum, Ap4A may function in the metabolic response to anaerobic conditions rather than in the response to oxidative stress.
Garrison
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Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.
Mathis
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SA
Barnes
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LD
D000332:Aerobiosis; D000693:Anaerobiosis; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007700:Kinetics; D010100:Oxygen / Q000494:pharmacology*; D010804:Physarum / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D015226:Dinucleoside Phosphates; C020733:diadenosine tetraphosphate; D006861:Hydrogen Peroxide; D010100:Oxygen