Myoglobin in heart-muscle preparations and the effect of nitrite treatment

Spectrophotometric studies on intact muscle. I. Components of the respiratory chain

The concentrations of the components of the respiratory chain were determined in a variety of intact skeletal muscles by a method of spectrophotometric observation of the transmitted light. In the case of the toad sartorius, these measurements were checked against isolated mitochondrial suspensions prepared from toad skeletal muscles. The relative concentrations of the respiratory components were found to be in reasonable agreement with those of various mitochondrial preparations of mammalian tissues and of the ones from toad skeletal muscle. The rather low cytochrome b and pyridine nucleotide levels in the anoxic minus oxygenated difference spectra were shown to be caused to a certain degree by a partial reduction during the resting steady state. Upon treatment with a strong, reducing agent or after long anoxia some absorption bands appeared with maxima at 591, 562 to 564, and 432 to 434 mmicro both in the intact and in the mitochondrial fractions of muscle tissue; they do not appear to be associated with the respiratory chain.

METMYOGLOBIN OXIDATION DURING ELECTRON TRANSPORT REACTIONS IN MITOCHONDRIA

Studies of the intracellular role of myoglobin were carried out by recording spectrophotometric changes in acid metmyoglobin and oxymyoglobin during electron transport reactions with mitochondria prepared from pigeon heart muscle by the method of Chance and Hagihara. The absorption peak of metmyoglobin at 409 mmicro disappeared when substrate was added to normal or antimycin-inhibited preparations, and was replaced by a new maximum at 423 to 424 mmicro, identified as due to the oxidation to ferrylmyoglobin. Further investigation revealed that the oxidation of metmyoglobin took place with the simultaneous oxidation of reduced flavoprotein. Hydrogen peroxide, formed by the reaction of reduced flavoprotein with oxygen, was considered to be the probable intermediate for the oxidation of metmyoglobin in experiments in which catalase was added as a competitor for the oxidant. When DPNH was added to the reaction mixture, the reductant acted to resynthesize the ferri-derivative by reaction with ferrylmyoglobin. Oxymyoglobin could not be used in place of metmyoglobin in these systems. Under the experimental conditions, oxymyoglobin dissociated when dissolved oxygen was depleted from the medium by enzyme oxidations; the resultant ferromyoglobin underwent oxidation to metmyoglobin.

Some effects of adrenaline on anion transport and nitrite-induced methaemoglobin formation in the rainbow trout (Salmo gairdneri Richardson)

The effects of adrenaline on branchial anion transport and nitrite-induced methaemoglobinaemia have been investigated in rainbow trout. Nitrite uptake and efflux results suggest that adrenaline effects a net anion efflux principally by stimulation of the unidirectional branchial anion efflux. In oxygenated whole blood nitrite-induced methaemogloblin was significantly reduced in the presence of adrenaline. The physiological and environmental consequences of nitrite-induced stress are discussed.