In Vitro Ion and Water Movement in Corneas of Rainbow Trout.

Cation concentration and water content were determined in the normal rainbow trout cornea, aqueous humor, lens, and vitreous humor. Anatomically the rainbow trout cornea possesses a thicker epithelium and a more prominent Bowman's membrane than those found in mammalian corneas. Descemet's membrane and the endothelium appear more primitive than their mammalian counterparts. In vitro, the cornea showed a limited permeability to both water and ions, and cornea! ion concentration appears to vary inversely with corneal hydration. The trout cornea was found to be a metabolically active tissue with a high sodium concentration. Data obtained from tritiated water experiynents suggest an exchange of water across the trout cornea which is considerably less than that observed in mammalian corneas. In the intact trout the relative permeability of the cornea should be less than that observed in vitro because of the presence of a viscous aqueous humor and an opposing hydrostatic pressure.