Effect of spermine on mitochondrial matrix calcium in relation to its enhancement of mitochondrial calcium uptake.
The mechanism of spermine-induced enhancement of mitochondrial Ca2+ uptake was explored using the fluorescent Ca2+ indicator Fluo-3/AM to measure the free matrix Ca2+ concentration. Simultaneously, the extramitochondrial Ca2+ concentration was registered by a Ca(2+)-ion selective electrode. Spermine lowered the extramitochondrial steady state Ca2+ concentration and at the same time induced a decrease of the intramitochondrial Ca2+ concentration. However, there is a concentration-dependent reversal of the stimulatory action of spermine, which may be explained by the existence of a second, low-affinity binding site for spermine which mediates an inhibition of uptake in spite of the existence of an inwardly directed Ca2+ gradient.
Rustenbeck
I
I
Institute of Pharmacology and Toxicology, University of Göttingen, Germany.
Eggers
G
G
Münster
W
W
Lenzen
S
S
D000814:Aniline Compounds; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D008839:Microelectrodes; D008930:Mitochondria, Liver / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence; D013096:Spermine / Q000494:pharmacology*; D014966:Xanthenes
D000814:Aniline Compounds; D014966:Xanthenes; C059715:Fluo-3; D013096:Spermine; D002118:Calcium