Polarographic observation of substrate-level phosphorylation and its stimulation by acetylcholine.
Substrate-level phosphorylation was observed under the conditions optimal for this process and opposite to those for oxidative phosphorylation. Polarographic registration of Ca2+ stimulated alpha-ketoglutarate oxidation and self-inhibition of uncoupled alpha-ketoglutarate (KG) oxidation was used. Acetylcholine (ACh) administration stimulated KG oxidation and substrate-level phosphorylation in isolated mitochondria. These effects are stronger in tissues with a higher level of endogenous acetylcholine, such as guinea pig liver vs rat liver and pancreas vs liver. The specific stimulation of KG oxidation by ACh is related to a decrease of succinate oxidation and is contrary to the specific stimulating effect of adrenaline on succinate oxidation. Therefore the existence of reciprocal hormone-substrate-nucleotide systems is suggested. The described set of conditions optimal for substrate-level phosphorylation observation by polarographic registration of respiration is as convenient as the ADP test for the investigation of oxidative phosphorylation.
Kondrashova
M N
MN
Institute of Biological Physics, USSR Academy of Sciences, Moscow.
Doliba
N M
NM
D000109:Acetylcholine / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007656:Ketoglutaric Acids / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010179:Pancreas / Q000378:metabolism; D010766:Phosphorylation; D011048:Polarography; D051381:Rats; D011919:Rats, Inbred Strains; D013386:Succinates / Q000378:metabolism*; D019802:Succinic Acid
D007656:Ketoglutaric Acids; D013386:Succinates; D019802:Succinic Acid; D000109:Acetylcholine; D002118:Calcium