Effectiveness of Antimycin A, Oligomycin, and Sodium Cyanide as Inhibitors of Rat Bone Marrow Oxygen Utilization

The inhibition of oxygen consumption was studied in vitro using the metabolic inhibitors antimycin A, oligomycin, and sodium cyanide. Primary concern was to determine the rate and extent of oxidative inhibition upon intact rat bone marrow cells. At concentrations of 5 x 1()~ sodium cyanide, or higher, inhibition was total and immediate. At a concentration of 5 x 10~ it was found that sodium cyanide was not significantly inhibitory during the first ten minutes of incubation. Antimycin A and oligomycin were found to be significantly inhibitory for oxygen consumption within two minutes at the 5 x 1()~ and 5 x 1()~ concentrations. At concentrations higher than 5 x 10^ antimycin A and oligomycin were equally effective inhibitors of oxygen consumption. Use of lower concentrations of the two antibiotics showed that oligomycin was slightly more inhibitory to bone marrow oxygen consumption than antimicycin A. OHIO J. SCI. 76(3): 139, 1976 The inhibitory qualities of antimycin A (Dickson et al, 1971; Georg et al, 1971; Kanivga et al, 1969; Perry and Williams, 1971; Rieske, 1971) and oligomycin (Fairhurst and Elison, 1964; Yates, 1966; Pinna, 1967; Hackenbrock et al, 1971; Sabadie-Pialoux and Gautheron, 1971) have received considerable attention. Most of this work, however, was concerned with isolated cellular fractions, or specific biochemical reactions. It was of interest to determine the sensitivity of intact bone marrow cells to these oxidative inhibitors by measuring oxygen utilization rates Sodium cyanide inhibition was used as a reference point, because of its historical use as an oxidative inhibitor. MATERIALS AND METHODS Male Holtzman rats 42 ±2 days age were killed by cervical dislocation and the two femora and tibiae removed. The bones were split lengthwise and the marrow teased apart in Tyrode's solution adjusted to 310 milliosmoles/liter and a pH of 7.35. Cell suspensions were obtained by passing the bone marrow cells successively through two 100-mesh stainless steel screens. Determinations of Manuscript received January 12, 1976 (#76-2). cell counts were made on aliquots of the bone marrow suspension. After taking a sample of the bone marrow suspension for counting, an aliquot was diluted to contain 8 x 10 cells per 5 ml of Tyrode's solution. Five milliliters of this suspension was placed into each of two sample chambers of a YSI model 53 biologic oxygen monitor equilibrated, and measured with an oxygen electrode for 20 minutes at 37°C to determine oxygen consumption. Only one chamber had inhibitor added providing each experimental determination with a paired control. Antimycin A and oligomycin (consisted of 15 percent A and 85 percent B) were obtained from The Sigma Chemical Co. Ten trials were performed at each of three concentrations for each metabolic inhibitor, antimycin A, oligomycin, and sodium cyanide.