mRNA from corneal epithelium increases water permeability in Xenopus oocytes

HORWICH TAMARA; IBARRA CRISTINA; FORD PAULA; ZAMUDIO A; PARISI MARIO; CANDIA P

INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE

Association For Research In Vision And Ophthalmology (Arvo)

Año: 1995 vol. 36 p. 2772 - 2774

0146-0404

Purpose. To investigate the existence of a water channelin the frog corneal epithelium by studying the osmoticwater permeability (P,) of Xenopus oocytes expressingthe mRNA message from frog corneal epithelium.Methods. Total RNA was obtained from corneal epitheliumby a single-step phase separation method, and polyA+ RNA was isolated using oligo-dT columns. ThismRNA was injected into the oocytes. After a 48-hourincubation, oocyte volume changes elicited by a hypoosmoticsolution were measured with a computerizedvideo system.Results. Oocytes injected with 50 nl mRNA (1 //g///l)showed a significant increase in Pt compared to waterinjectedcontrols (8.4 ± 1.5 to 17.5 ±1.9 cm-sec"1 X10~4, P < 0.005). mRNA-injected oocytes exposed to ahigher external [Cl~] showed a heightened permeability.Furthermore, P, of oocytes exposed to a solutioncontaining the recognized water-channel blocker HgClywas significandy lower than the Pr of mRNA-injectedoocytes not exposed to HgCl2.Conclusions. Evidence was found for a water channel inthe frog corneal epithelium because oocytes injectedwith the epithelial mRNA manifested increased waterpermeability. The increase in water permeability waslarger in the presence of external Cl~ and was inhibitedby HgCl´2. This finding correlates with measurements ofPr in the intact epithelium in which apical Cl~ inducedan increase in transepithelial water permeability preventedby HgCl2.