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THE STIMULATION BY BICARBONATE OF ADENOSINE TRIPHOSPHATASE ACTIVITY IN THE SEMINIFEROUS TUBULES OF RODENTS AND THE LACK OF EFFECT OF OUABAIN

Summary.: Considerable ATPase activity was demonstrated in homogenates of testes and of isolated seminiferous tubules, but ouabain had no consistent effect on the activity suggesting that most of the ATPase is not the sodium and potassium stimulated ATPase usually associated with ion transport. However, the substitution of bicarbonate for chloride ions in assays at pH 8·4 caused a significant stimulation in ATPase activity of homogenates of testes or isolated seminiferous tubules and liver mitochondria. When the homogenates were fractionated on sucrose gradients, most of the ATPase activity was found associated with mitochondria. Because of this large amount of mitochondrial ATPase present, it is unlikely that we could have demonstrated the amounts of transport ATPase which would account for the amount of fluid secreted by the testis.