November 1994
Volume 35, Issue 12
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Articles  |   November 1994
Osmoregulatory alterations in myo-inositol uptake by bovine lens epithelial cells. Part 4: Induction pattern of Na(+)-myo-inositol cotransporter mRNA under hypertonic conditions denoting an early-onset, interactive, protective mechanism against water stress.
Author Affiliations
  • C Zhou
    Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth/North Texas Eye Research Institute 76107.
  • H Q Chen
    Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth/North Texas Eye Research Institute 76107.
  • R Reeves
    Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth/North Texas Eye Research Institute 76107.
  • N Agarwal
    Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth/North Texas Eye Research Institute 76107.
  • P R Cammarata
    Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth/North Texas Eye Research Institute 76107.
Investigative Ophthalmology & Visual Science November 1994, Vol.35, 4118-4125. doi:
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      C Zhou, H Q Chen, R Reeves, N Agarwal, P R Cammarata; Osmoregulatory alterations in myo-inositol uptake by bovine lens epithelial cells. Part 4: Induction pattern of Na(+)-myo-inositol cotransporter mRNA under hypertonic conditions denoting an early-onset, interactive, protective mechanism against water stress.. Invest. Ophthalmol. Vis. Sci. 1994;35(12):4118-4125.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: To examine the effect of hypertonicity on the induction of the Na(+)-myo-inositol (Na(+)-MI) cotransporter(s) in cultured bovine lens epithelial cells (BLECs). METHODS: Na(+)-MI cotransporter 626-bp reverse transcription-polymerase chain reaction product amplified from lens cell RNA and aldose reductase (AR) cDNA probes were used to measure respective mRNA content by Northern blot analysis. RESULTS: Northern blot analysis of BLEC mRNA hybridized to Na(+)-MI cotransporter cDNA showed that Na(+)-MI cotransporter mRNA increased when secondary cultures of BLECs were exposed to physiological medium supplemented with 116 mmol/l NaCl. A time course further revealed a maximal increase in Na(+)-MI cotransporter mRNA by 8 hours. Thereafter, the level of Na(+)-MI cotransporter mRNA steadily declined for the duration of the 72-hour incubation period despite continuous exposure of BLECs to hypertonicity. AR mRNA levels maximally increased by 24 h of cell exposure to hypertonic condition. Unlike Na(+)-MI cotransporter mRNA, AR mRNA remained elevated throughout the duration of the experiment. Hypertonic exposure resulted in a steady state accumulation of myo-inositol and sorbitol for 6 days. Inhibition of sorbitol formation prompted the intracellular myo-inositol content to a higher level. CONCLUSIONS: These data suggest that enhanced MI transport and accumulation, as an adaptive osmoregulatory response to hypertonicity in cultured BLECs, is a primary, early-onset, protective mechanism against water stress, succeeded by, enhanced sorbitol formation and accumulation, a secondary, late-onset protective mechanism. The lens appears to respond to the preliminary stages of hyperosmotic stress by induction of Na(+)-MI cotransporter mRNA, indicating that the myo-inositol carrier protein(s) play an initial responsive role in the management of osmotic stress. Lens water stress management is interactive because myo-inositol and sorbitol levels are regulated in concert.

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