m‐Iodobenzylguanidine increases the mitochondrial Ca2+ pool in isolated hepatocytes

Abstract

The incubation of isolated hepatocytes with the inhibitor of protein mono ADP-ribosylation, m-iodobenzylguanidine (MIBG), resulted in an increase in the size of the mitochondrial Ca²⁺ pool, without alteration of the non-mitochondrial Ca²⁺ store(s). This increase was abolished when the cytosolic free Ca²⁺ concentration ([Ca²⁺]_i) was buffered by prior loading of the cells with fluo 3. Elevating [Ca²⁺]_i by releasing the endoplasmic reticular Ca²⁺ store with 2,5-di-(tert-butyl)-1,4-hydroquinone resulted in a synergistic increase in the magnitude of the mitochondrial Ca²⁺ pool. A role for protein ADP-ribosylation in the intracellular regulation of mitochondrial Ca²⁺ homeostasis is suggested.