Affinity of intramitochondrial granules for ruthenium red accompanying induced cell death in chick embryos

To test the hypothesis that ruthenium red binding of intramitochondrial granules might reflect an altered or pathological state of membranes associated with degeneration, embryos were treated with 6‐AN to induce cell death in cartilaginous skeletons of chick embryos. Cervical cartilage from normal, 6‐AN‐treated and nicotinamide‐alleviated 6‐AN embryos was examined ultrastructurally for presence of IM RR‐positive granules. Mitochondria of normal cervical chondroblasts which undergo normal phenotypic expression acquire RR‐positive granules, although few mature cells are observed in young embryos. Necrotic chondroblasts, chondroblasts in various stages of degeneration, and proliferating chondrogenic cells of 6‐AN‐treated embryos all demonstrated induced RR‐positive IM granules. Foci of degenerating chondroblasts, with mitochondria demonstrating RR granules, were observed infrequently in teratogen‐alleviated tissue. The cytological features induced by 6‐AN confirm its lethal effect and the degenerative effect on membranes presumably “unmasks” mitochondrial Ca‐affinity sites which then become RR‐positive. Cytochemical observations correspond with the biochemical and structural changes induced by 6‐AN and confirm the hypothesis that RR‐positive sites are the result of pathological changes.