It was revealed that glutamate (GLU) and a-ketoglutarate (KGL), the substrates involved in transamination, have reciprocal effects on the succinate-dependent processes of respiration, NADN reduction, as well as on the accumulation and stable retention of Ca²⁺ in heart and liver mitochondria of various animal species. The succinate-dependent absorption of Ca²⁺ was shown to be highly sensitive to changes in concentration ratios of GLU and KGL within the range 1:10 mM. The predominance of 10 mM KGL blocked the 1 mM GLU-activated Ca²⁺ absorption. A similar effect was produced by 1 mM phosphoenolpyruvate (PEP). The block produced by KGL and/or PEP (sources of oxalacetate and GTP) but not by aminoacetate, inhibitor of transaminases, was eliminated by 10 mM GLU. A regulatory role of transamination in the succinate-dependent absorption of Ca²⁺ in animal tissue mitochondria was shown.