TY - JOUR
T1 - 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
AU - Cammarata, Patrick R.
AU - Chen, Hai Qing
AU - Zhou, Cheng
AU - Reeves, Rustin
PY - 1994/7
Y1 - 1994/7
N2 - 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).
AB - 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).
KW - Cultured lens epithelial cells
KW - Hypertonicity
KW - Na-myo-inositol cotransport protein(s)
KW - Osmoregulation
KW - Protein synthesis
UR - http://www.scopus.com/inward/record.url?scp=0028023645&partnerID=8YFLogxK
U2 - 10.1006/exer.1994.1083
DO - 10.1006/exer.1994.1083
M3 - Article
C2 - 7835400
AN - SCOPUS:0028023645
VL - 59
SP - 83
EP - 90
JO - Experimental Eye Research
JF - Experimental Eye Research
SN - 0014-4835
IS - 1
ER -