Abstract
Abstract
Purpose:
To determine whether a nonprotein lipophilic carrier, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), can remove all-trans retinol from rod photoreceptor outer segments. All-trans retinol is generated in rod outer segments after light exposure. It is highly insoluble, and its efficient transport across extra- and intracellular aqueous space requires specialized carriers.
Methods:
Experiments were carried out with isolated frog rod photoreceptor cells. The removal of all-trans retinol by different concentrations of this carrier was measured by imaging its fluorescence in single-rod photoreceptors.
Results:
HP-β-CD concentrations >0.3 mM significantly increased the rate of all-trans retinol removal. The rate of removal increased linearly with carrier concentration, with a slope of 0.0058 min−1/mM.
Conclusions:
The effectiveness of HP-β-CD shows that a specialized interaction with the cell membrane is not necessary for the efficient transfer of all-trans retinol between the cell membrane and the carrier. The transfer occurs through a collision-based mechanism, as indicated by the linear increase of the rate of removal with the carrier concentration.
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