Studies on the efflux of metalloporphyrin from rat liver mitochondria. Effect of K+ and other cations.
The mechanism by which metalloporphyrins synthesized within the mitochondria escape to the incubation medium was studied in isolated rat liver mitochondria. In a low-ionic-strength sucrose medium, the efflux of metalloporphyrins is markedly decreased when K+ (greater than 10 mM) is added. The effect of K+ is not dependent on the energy state of the mitochondria and it can in part be abolished by adding globin, but not albumin. K+ also decreases the uptake of porphyrins by the mitochondria and thereby the rate of synthesis of metalloporphyrins. Qualitatively similar results are found with Na+, Li+, Mg2+ and Ca2+. Quantitatively, however, the efficiency of cations to inhibit the release of metalloporphyrins decreases in the order: Mg2+ greater than Ca2+ greater than K+ greater than Li+ greater than Na+. Co-protoporhyrin behaves essentially as Co-deuteroporphyrin. The results provide further evidence that the efflux of metalloporphyrins from the mitochondria depends on haem-binding ligands of the suspending medium and also on the ionic strength of the incubation medium.
D000818:Animals; D002412:Cations / Q000494:pharmacology; D003905:Deuteroporphyrins / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008665:Metalloporphyrins / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology*; D011524:Protoporphyrins / Q000378:metabolism; D051381:Rats; D013367:Submitochondrial Particles / Q000378:metabolism
D002412:Cations; D003905:Deuteroporphyrins; D008665:Metalloporphyrins; D011524:Protoporphyrins; D011188:Potassium