The effect of extracellular Ca and Mg on mitochondrial ultrastructure in isolated intact neurons.
The ultrastructural transformations of mitochondria in isolated crayfish neurons were studied after incubation of the cells in saline media containing different Ca2+ and Mg2+ concentrations. Incubation in a 5-fold higher Ca concentration resulted in the swelling of mitochondria that was prevented by the addition of the calcium channel blocker, verapamil. Exposure of the cells to Mg2+-depleted medium induced swelling of all the mitochondria, followed by substantial shrinkage of most of them. The absence of Ca as well as the presence of verapamil in Mg2+-free medium led to the inhibition of mitochondrial swelling and to a strong contraction of the mitochondria after 1 h incubation. The omission of Ca2+ from the saline medium or the addition of Ca2+-ionophore A23187 in the presence of Ca2+ resulted in strong mitochondrial shrinkage. These structural alterations of mitochondria are interpreted as an osmotic response of the inner mitochondrial membranes to changes in their potassium transport, induced by a disturbance in the cellular and mitochondrial Ca2+-Mg2+ homeostasis.
D000818:Animals; D003400:Astacoidea; D002118:Calcium / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology*; D008854:Microscopy, Electron; D008928:Mitochondria / Q000187:drug effects / Q000648:ultrastructure*; D009474:Neurons / Q000187:drug effects / Q000648:ultrastructure*
D008274:Magnesium; D002118:Calcium