title: Priming of the fluid pump by osmotic gradients across rabbit corneal endothelium.
abstract: The present study shows that the inclusion of 5% Dextran (average mol. wt. 40 000) in solutions to preserve in vitro rabbit corneal endothelium induces a sizable osmotic flow across the preparation which is superimposed on the existing fluid transport. Furthermore, even after fluid transport ceases due to in vitro deterioration, the Dextran-induced flow remains for some addition time. The osmotic permeability was 162 +/- 17 micrometer/s in the presence of glucose and 451 +/- 84 micrometer/s in its absence. The latter, comparatively high value suggests that such osmotic flow traverses the intracellular junctions. In addition, temporary (10--15 min) imposition of an osmotic gradient has a separate stimulatory 'priming' effect on the rate of fluid transport. Thus, the rate of fluid pumping increased by about 40% after challenge with Dextran. It was further noted that, after addition of Dextran, preparations in the absence of glucose escape gross deterioration for a time longer than those in the presence of glucose. On the other hand, mere addition of Dextran to a glucose-containing solution does not appear to prolong the estimated 'survival time' of the pumping mechanism. The sizable osmotic flows and the priming effect described here may provide a physiological context with which previously described Dextran effects on cornea preservation can now be compared.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003315:Cornea / Q000378:metabolism*; D003911:Dextrans / Q000494:pharmacology*; D004727:Endothelium / Q000378:metabolism; D009997:Osmotic Pressure; D010539:Permeability; D011817:Rabbits; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000187:drug effects*
chemical_list: D003911:Dextrans