Inhibitory effect of A 23187 on protein synthesis in isolated murine hepatocytes

The effect of the Ca ionophore A 23187 on amino acid incorporation into protein, on gluconeogenesis and on synthesis of some eicosanoids was investigated in isolated mouse hepatocytes (i) in the presence of 2.5 mM Ca2+, (ii) in the absence of Ca2+ and in the presence of 0.2 mM EGTA, (iii) after calcium depletion. A 23187 inhibited amino acid incorporation into protein both in the presence and in the absence of Ca2+ in a concentration dependent manner, whereas in the absence of Ca2+ the known stimulating effects of A 23187 on eicosanoid synthesis could not be detected. In hepatocytes prepared from 24 h starved mice A 23187 increased the rate of gluconeogenesis and similarly to eicosanoid synthesis this stimulation in the absence of Ca2+ could not be observed. On the other hand, after calcium depletion the inhibition of protein synthesis by A 23187 was markedly moderated. It is concluded that the effect of A 23187 on protein synthesis is also related to its ionophoretic effect but calcium sensitivity in this effect is smaller than in gluconeogenesis or eicosanoid synthesis.