Energizing an invertebrate embryo: bafilomycin-dependent respiration and the metabolic cost of proton pumping by the V-ATPase.
We examine herein the contribution of V-ATPase activity to the energy budget of aerobically developing embryos of Artemia franciscana and discuss the results in the context of quiescence under anoxia. (31)P-NMR analysis indicates that intracellular pH and NTP levels are unaffected by acute incubation of dechorionated embryos with the V-ATPase inhibitor, bafilomycin A(1). Bafilomycin A(1) also has no significant effect on oxygen consumption by isolated mitochondria. Taken together, these data indicate that bafilomycin does not affect energy-producing pathways in the developing embryo. However, the V-ATPase inhibitor exhibits a concentration-dependent inhibition of oxygen consumption in aerobic embryos. A conservative analysis of respirometric data indicates that proton pumping by the V-ATPase, and processes immediately dependent on this activity, constitutes approximately 31% of the aerobic energy budget of the preemergent embryo. Given the complete absence of detectable Na(+)K(+)-ATPase activity during the first hours of aerobic development, it is plausible that the V-ATPase is performing a role in both the acidification of intracellular compartments and the energization of plasma membranes. Importantly, the high metabolic cost associated with maintaining these diverse proton gradients requires that V-ATPase activity be downregulated under anoxia in order to attain the almost complete metabolic depression observed in the quiescent embryo.
Covi
Joseph A
JA
Division of Cellular, Developmental, and Integrative Biology, Department of Biological Science, Louisiana State University, Baton Rouge, Louisiana 70803, USA. jcovil@lsu.edu
Hand
Steven C
SC
D000818:Animals; D001156:Artemia / Q000196:embryology* / Q000201:enzymology / Q000378:metabolism*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D018942:Macrolides; C057620:bafilomycin A; D025262:Vacuolar Proton-Translocating ATPases