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Osmoregulatory Alterations in Myo-inositol Uptake by Bovine Lens Epithelial Cells. III. Effects of Cycloheximide and Colchicine on Na+-Myo-inositol Cotransporter Activity Under Hypertonic Conditions, Inhibition of a Plasma Membrane Osmotic Stress Protein

Authors
Journal
Experimental Eye Research
0014-4835
Publisher
Elsevier
Publication Date
Volume
59
Issue
1
Identifiers
DOI: 10.1006/exer.1994.1083
Keywords
  • Hypertonicity
  • Protein Synthesis
  • Na+-Myo-Inositol Cotransport Protein(S)
  • Osmoregulation
  • Cultured Lens Epithelial Cells
Disciplines
  • Biology

Abstract

Abstract Cultured bovine lens epithelial cells adapt to hypertonic sodium stress via an increase in Na +-myo-inositol cotransporter activity and accumulate myo-inositol. At least 12 hr of hypertonic exposure was necessary to enhance myo-inositol accumulation; and thereafter, uptake activity continued to increase throughout the duration of a 72-hr exposure period. Switching from hypertonic to isotonic medium for 24 hr reversed the otherwise elevated accumulation activity. The protein synthesis inhibitor, cycloheximide, did not affect myo-inositol uptake in isotonic medium but markedly decreased myo-inositol uptake in hypertonic medium. Cells exposed to hypertonic conditions and the microtubule disrupter, colchicine, similarly showed marked impairment of the otherwise enhanced myo-inositol uptake. These studies indicated that hypertonicity-induced elevation of Na +-myo-inositol cotransporter activity in cultured bovine lens epithelial cells is not solely attributed to the increased sodium gradient alone, but rather involves increased de novo synthesis of the Na +-myo-inositol cotransporter protein(s).

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