Effects of hydrostatic pressure on Na transport in the freshwater crayfish, Procambarus clarkii

Effect of high hydrostatic pressure on 86Rb+ influx in the erythrocyte of the plaice (Pleuronectes platessa)

1. 86Rb+ influx in the erythrocyte of the plaice (Pleuronectes platessa) has been measured at hydrostatic pressures between 1 and 600 atm at 10 degrees C. 2. The measurements were performed with an experimental medium containing 1% (w/v) bovine serum albumin. In this medium the cells achieved a steady state level of ionic regulation. 3. At normal atmospheric pressure 46% of the 86Rb+ influx was inhibited by furosemide while 42% was inhibited by ouabain, the remainder being inhibited by neither drug. 4. It was found that all three fluxes defined by these drugs were sensitive to pressure. 5. The ouabain sensitive influx was progressively inhibited by increasing pressure, the inhibition at 600 atm being 30%. 6. The furosemide sensitive influx was inhibited by 35% between 100 and 600 atm. 7. In contrast the ouabain + furosemide insensitive influx was doubled by 400 atm. 8. This pattern of pressure inhibition and stimulation resembles that seen in comparable studies in human erythrocytes.

The ionic composition of the plasma and erythrocytes of deep sea fish

This paper reports measurements of the plasma osmolarities, the main inorganic ions and the concentrations of plasma proteins in nine species of deep sea fish from depths of 900-4,000 m. Chloride and magnesium values are high compared to those of shallow water fish. These ions may be contaminants from sea water either contributing to, or resulting from, the animals' moribund condition. They may also contribute to the failure of isolated erythrocytes to show ionic regulation even after being restored to their normal high pressure.

The effects of pressure on the molecular structure and physiological functions of cell membranes

The effects of high pressure on the phase state and molecular structure of pure lipid bilayers are discussed. The relations of delta H, delta S and delta V in phase transitions are straightforward and are discernible in heterogeneous bilayers in natural membranes. The effects of pressure on the dynamic properties of bilayer constituents are less clearly understood, but order parameters obtained at pressure by different techniques show agreement. The extent and significance of hydration is poorly understood. Four physiological functions are discussed: passive permeability, active transport, membrane excitability and synaptic transmission. It is shown that a full interpretation of the kinetic effects of pressure on these processes requires much more detailed molecular information than is available at present.