Effect of Metabolic Depletion on the Membrane Permeability of Smooth Muscle Cells and its Modification by La³⁺

Abstract

IN cellular ion exchange studies it is usually assumed that inhibition of metabolism does not affect the passive membrane characteristics and that the concomitant modifications of the ion exchange are largely caused by a deficient energy supply to the active ion transport systems. Our study of the ion distribution and the extracellular space of taenia coli cells revealed, however, that the ¹⁴C-sorbitol and ¹⁴C-sucrose space of tissues, increased over control values during exposure to N₂ agitated glucose-free solution. We prevented this extra sorbitol uptake by addition of 10 mM La³⁺, which also decreases membrane permeability to cations^1,2. Since La³⁺ was also able to partially reverse the increased membrane permeability caused by metabolic depletion we were able to trap ¹⁴C-sorbitol molecules and thus prove their penetration into the cells.