Activation of calcium uptake in rat liver mitochondria by aminoglucoside antibiotics

Ca uptake in rat liver mitochondria is accelerated by various aminoglucoside antibiotics and, to a lesser degree, by triethylenetetramine and by protamine. With 1 mM Mg2+ and at a concentration of Ca2+ = 2 microM maximal (about six-fold) activation is achieved with 20 microM neomycin; at higher concentrations of the antibiotic the velocity of Ca uptake decreases. Activation to the same degree by gentamicin, kanamycin or streptomycin requires higher concentrations of the antibiotics. The reason for the acceleration of Ca uptake by neomycin is an allosteric alteration of the kinetics corresponding to that previously observed in the presence of spermine. The conformity with effects of spermine and possible inferences of that conformity are discussed.