Myo-inositol (MI) is involved in the adaptation to hyperosmolality. Its uptake by rat inner medullary collecting duct (RIMCD) cells has not been studied. Compared with cells grown in isotonic media, those grown in hyperosmolality display marked enhancement in [3H]MI uptake [counts/min (cpm)·μg protein-1·2 h-1] from 217 ± 23 to 718 ± 64, P < 0.001. This is mimicked by the supplementation with 300 mM mannitol (638 ± 59, P < 0.001) but not by 300 mM area. The increment in [3H]MI is observed at 37°C but not at 4°C. MI uptake is Na+ dependent in cells grown both in hyperosmolal or isotonic media. At least 12 h of hyperosmolality are needed to enhance MI uptake, and reexposure to isotonic media for at least 24 h is required for the enhancement to reverse. The effects of the microtubular inhibitor, nocodazole (10 μg/ml), and the protein synthesis inhibitor, cycloheximide (30 μg/ml), were studied. Cells grown with nocodazole show unimpaired enhancement of MI uptake. Cycloheximide exposure (16 h) does not affect MI uptake in isotonic media (182 ± 23 vs. 191 ± 15), but inhibited enhanced MI uptake in hyperosmolality (822 ± 53 in the absence vs. 331 ± 24 in the presence of cycloheximide, P < 0.001). We conclude that hyperosmolality stimulates the synthesis of a protein, most likely an Na-MI cotransporter, that markedly enhances MI uptake. This process may be critical to the osmoregulation of RIMCD cells.
|Original language||English (US)|
|Journal||American Journal of Physiology - Renal Fluid and Electrolyte Physiology|
|Issue number||5 29-5|
|State||Published - 1991|
- Protein synthesis
ASJC Scopus subject areas