[The inhibitory effect of magnesium on mitochondrial calcium uptake in ischemic and reperfused rat hearts].
Several studies suggest that the protection exerted by Mg2+ on the reperfused myocardium may be mostly due to its competitive effect with respect to Ca2+. The aim of this research was to evaluate the inhibitory action of Mg2+ on mitochondrial Ca2+ uptake in the reperfused myocardium. Hearts of male Wistar rats (250-300 g) were isolated and perfused by the Langendorff technique. Aerobic control hearts (n = 6) were perfused with a constant flow of 10 ml/min/g for 65 min. In a second group (n = 6) the hearts were aerobically equilibrated for 20 min, then subjected to 30 min of ischemia (98% reduction of coronary flow) and subsequently reperfused for 15 min at the same preischemic flow. The hearts of both groups were electrically stimulated at 300 b/min. Then, the hearts were pooled in groups of 2 each and homogenized for the isolation of mitochondria. One part of mitochondrial suspension was used to evaluate the respiratory function by a polarographic technique. The remaining part was incubated with fura-2/AM for 10 min at 30 degrees C in order to determine the kinetics of Ca2+ transport within mitochondria in the presence of succinate as substrate. Ca2+ uptake was reduced in the mitochondria of reperfused hearts with respect to control, particularly in the presence of elevated extramitochondrial Ca2+ concentrations (greater than 10 nM). On the contrary the initial rate of Ca2+ uptake was increased in the reperfused mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)
Muscari
C
C
Dipartimento di Biochimica, Università degli Studi, Bologna.
Pretolani
M
M
Guarnieri
C
C
Caldarera
C M
CM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003327:Coronary Disease / Q000378:metabolism*; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D008274:Magnesium; D002118:Calcium
Effetto inibitore del magnesio sull'uptake del calcio mitocondriale in cuori ischemici e riperfusi di ratto.