| Abstrakt: |
Extract: Cation transport in a population of stomatocytic red blood cells (RBC) is abnormal in the following respects. First, active transport against a gradient, defined as the nonisotopic net accumulation of Na+or loss of K+induced by 0.1 mM ouabain, is markedly elevated (7.3 and 6.3 mEq/liter cells/hr for Na+and K+, respectively), but the Na+: K+active transport ratio is normal. Apparent uncoupling of the Na+and K+isotope transport is due to disproportionately increased ouabain-sensitive 24Na+-23Na+exchange (32.7 mEq/liter cells/hr), which is measured as a portion of 24Na+isotope efflux. Second, cation transport is unresponsive to variations in internal Na+concentration but decreases with decreasing extracellular Na+.Speculation: In the family we have studied, the clinical disorder, hereditary stomatocytosis, has been shown to be an autosomal dominant trait. The disorder may be due, therefore, to the transcription of an abnormal membrane protein which leads to altered shape, abnormal cation permeability, and reduced cell survival in vivo. The abnormal protein may be structural, leading to the shape alteration, and functional, leading to the alteration in permeability and transport. The abnormality, hereditary stomatocytosis, is a heterogeneous group of disorders; hence, the observations in this family may not reflect the specific membrane protein defect in all cases. |
