Transmembrane Transport of Water and Urea in Rat Corneal Endothelial Cells

---

Lyubov E. Katkova^1,2,a#, Galina S. Baturina^1,2#, Igor A. Iskakov³, and Evgeny I. Solenov^1,4,b*

¹Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia

²Novosibirsk National Research State University (NSU), 630090 Novosibirsk, Russia

³Novosibirsk Branch, Federal State Autonomous Institution “National Medical Research Center “Interbranch Scientific and Technical Complex “Eye Microsurgery” named after Academician S. N. Fedorov” of the Ministry of Health of the Russian Federation, 630096 Novosibirsk, Russia

⁴Novosibirsk State Technical University (NSTU), 630087 Novosibirsk, Russia

^* To whom correspondence should be addressed.

^# These authors contributed equally to the work.

Received: July 3, 2025; Revised: September 12, 2025; Accepted: September 25, 2025

---

This study investigated permeability of the apical and basolateral membranes of rat corneal endothelial cells to water and urea. We demonstrated that the apparent water permeability of the basolateral membrane of endothelial cells (4.43E−05 ± 7.57E−07 cm/s) is more than three times higher than that of the apical membrane (1.21E−05 ± 1.03E−07 cm/s). Permeability of the basolateral membrane to urea (1.23E−04 ± 1.56E−06 cm/s) was statistically significantly higher than that of the apical membrane (9.52E−05 ± 1.02E−06 cm/s) by approximately 30%. We examined contribution of the phloretin-inhibited urea transport across the apical and basolateral membranes in these cells. Phloretin at concentration of 0.1 mM significantly reduced urea permeability by more than 20% through both the apical and basolateral membranes. The results suggest that the compositions of transporters involved in water transport in the apical and basolateral membranes differ significantly. It is hypothesized that high apparent water permeability of the basolateral membrane of endothelial cells is due to contribution of the concomitant water transport with ions involved in active transport processes. Presence of the phloretin-sensitive urea transporters in the plasma membrane of endothelial cells, likely involved in its transcellular transport, has been demonstrated. The results indicate potential significance of urea for corneal function.

---

KEY WORDS: corneal endothelium, transmembrane transport, water permeability, urea permeability, phloretin

DOI: 10.1134/S0006297925601881

Publisher’s Note. Pleiades Publishing remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

---