This content is PDF only. Please click on the PDF icon to access.
Abstract
This paper shows that significant and variable changes in cation composition of intracellular fluid of the lens occur when the concentration of Na+ in media is isosmotically replaced by a number of frequently used Na+ substitutes. The concentrations of sodium, potassium, and various substances (TEA, choline, Li, Tris, K, Cs, Rb, and sucrose) used to replace isosmotically 50 mmoles per liter of sodium in media were determined in intracellular fluid (fiber water) of rabbit lenses following 20 hours of culture. The sodium substitutes accumulate in the lens in concentrations varying from 7 mM. for TEA to over 100 mM. for potassium and rubidium. Total cation concentration is reduced by choline, increased by rubidium, cesium, and sucrose, and not significantly altered by other substitutes. Accumulation of organic cations and lithium is approximately balanced by loss of potassium, whereas accumulation of cesium and rubidium exceeds loss of potassium by approximately 20 mM., and loss of sodium and potassium combined by 15 mM. It is suggested that the observed changes in cation composition of intracellular fluid of the lens could affect transport processes independent from reduction in concentration of extracellular sodium.