Effects of demethylchlortetracycline phototoxicity on the structure and functions of rat liver mitochondria

— The phototoxic effects of demethylchlortetracycline (DMCT) with UVA radiation on isolated rat liver mitochondria were studied. DMCT at concentration of 21.5 μM with 5.53 times 10−2 J cm'of UVA was found to be a potent uncoupler of oxidative phosphorylation. DMCT alone also uncoupled mitochondria but at higher concentrations (105 μM). ATPase activity was remarkably induced in mitochondria exposed to DMCT (21.5 μM) plus UVA (120% of DNP-stimulated ATPase activity). Content of ATP in such mitochondria when measured after addition of ADP was much smaller than that in control mitochondria. Ultrastructurally, mitochondria treated either with DMCT (21.5 μM) or with UVA alone stayed in the condensed configuration. On the other hand, uncoupled mitochondria treated with DMCT plus UVA became swollen and were changed into the orthodox configuration.