[Effect of cations and DNP on ATPase activity in different tissue fractions of birds' brains]

ATP-ase activity and the effect of cations (Na+, K+, Mg2+, Ca2+) and DNP on its activity have been studied in avian brain homogenates and mitochondrial and supernatant fractions (microsomes + hyaloplasma). Highest levels of Na+ + K+ -stimulated ATP-ase activity has been shown in avian brain crude mitochondrial fraction, next in supernatant and lowest in homogenates. Following three-fold freezing and thawing, enzyme activity in homogenates and mitochondrial fractions increases considerably and decreases in the supernatant. Highest Mg2+ -stimulated ATP-ase activity is found in avian brain homogenates, next in mitochondrial fractions and supernatants. Mg2+ -stimulated ATP-ase activity is not changed considerably following three-fold freezing and thawing of brain preparations. Highest Ca2+ -stimulated ATP-ase activity has been observed in the supernatant fraction and its activity is considerably reduced following freezing and thawing. Avian brain mitochondrial fractions have high DNP-stimulated ATP-ase activity. Following freezing and thawing of brain preparations DNP-stimulated ATP-ase activity is not changed considerably. The results obtained indicate that in avian brain homogenates and other preparations, cation and DNP-stimulated ATP-ase have different activities. Three-fold freezing and thawing of brain tissue preparations affect these activities differentially.