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A method for oxygenating and mixing suspensions of turbot Psetta maxima red blood cells (RBC) was tested in 31P nuclear magnetic resonance (NMR) spectroscopy. In normoxia, the levels of inorganic phosphate (Pi) and nucleoside triphosphates (NTP) were stable up to 140 min and intracellular pH (pHi) was maintained and decreased oxygen partial pressure ( PO 2) from 30 to 15 and 600 Pa produced a significant fall in the intensity of NTP resonance, balanced by an increase in the Pi signal. Treatment of RBC with 0· 5 M isoproterenol during hypoxia exposure did not affect the pattern of changes in NTP or pHi induced by hypoxia and the effect was manifest only on Pi levels. [ABSTRACT FROM AUTHOR]

1. A rapid method for the determination of AMP and IMP by HPLC is described. 2. Its application to the assay of AMP deaminase allows the specific determination of enzyme activities in crude extracts, eliminating any interference by other enzyme systems (5'-nucleotidase and adenosine deaminase). 3. The method was routinely used for the determination of the AMP deaminase activity in the muscles of marine animals.

1. AMP deaminase from thoroughbred horse muscle was purified to apparent homogeneity and its regulatory properties were determined at pH 6.5 and 7.4. 2. The results are discussed in relation to the potential role of muscle AMP deaminase during exercise and the existence of two molecular forms depending on the pH.

Three isolation procedures were used to test the labilization of the lysosomes after adaptation of the animals to seawater, starvation or acute and chronic treatments with 2,4,5-T, an organochlorine pesticide. The lysosomes from gill and liver had different properties with respect to their resistance to osmotic and mechanical shocks, or treatments with digitonin. Starvation induced a significant labilization of the lysosomes in liver, but not in gill. Salinity changes were without effect on the stability of the gill lysosomes, but induced an increase of the specific activity of the lysosomal enzyme beta-acetylglucosaminidase. Acute treatments with 2,4,5-T increased lysosomal fragility in the gill but not in the liver, while chronic treatments with this herbicide increased lysosomal lability in the two tissues. Liver lysosomes were much more susceptible to in vitro treatments with 2,4,5-T than gill lysosomes. The results are discussed with respect to the different functions of gill and liver, their exposure to the environment, and the possible discrimination between different lysosomal populations.