Membrane ATPase and electrolyte levels in marsupial erythrocytes

Abstract

• 1.

  1. Individuals of the Australian marsupial species, the possum (Trichosurus vulpecula), differ in erythrocyte cation concentration. ATPase activity was measured in the fragmented membranes of erythrocytes in which potassium predominates (HK cells) and in which sodium predominates (LK cells). A comparison was made with erythrocyte membrane ATPase activity in the marsupial quokka (Setonyx brachyurus) in which sodium and potassium are present in approximately equal concentration.

• 2.

  2. All erythrocyte preparations showed basal ATPase activity. Significant (Na⁺-K⁺)-activated ATPase was present only in HK possum and quokka cells, absolute values and values relative to basal ATPase being higher in HK possum than in quokka cells.

• 3.

  3. These results suggest that the low erythrocyte potassium concentrations in LK possums may be due to the absence of (Na⁺-K⁺)-activated ATPase and pump activity in their cell membranes.