The Effect of Reaction Media on the Coupling and Uncoupling of Respiration in Corn Mitochondria

The coupling and uncoupling properties of isolated corn mitochondria were analyzed using three substrates in Tris buffered sucrose and KC1 reaction medias containing inorganic phosphate (P_i), bovine serum albumin (BSA), or P_i and BSA. In these media, without other cofactors, respiratory control (RCR) and ADP/O ratios, and the respiratory burst affected by dinitrophenol (DNP), gramicidin D, calcium chloride and ADP were measured. Bovine serum albumin enhanced the respiratory burst caused by DNP and gramicidin D in the absence of P_i, and in most instances enhanced the stimulation of oxygen uptake by ADP and calcium chloride in the presence of P_i. Mitochondria oxidizing succinate, malate-pyruvate or NADH exhibited better RCR and ADP/O ratios in buffered 200 mM KCl than they did in buffered 300 mM sucrose. In all instances RCR and ADP/O ratios were enhanced in reaction medias containing BSA.