Epithelial Fluid Transport—A Century of InvestigationR. Spring

Summary—A hundred years of progress? Both E. Waymouth Reid and Peter Currandeveloped a remarkably clear understanding ofthe mechanism of fluid transport by epithelia.Although we have added many refinements totheir concepts, sometimes wandering afield, ourknowledge of the crucial details still exhibits sur-prising gaps. Molecular methods combined withfunctional assays are opening the door to under-standing the process of fluid transport, but thetechnical impediments imposed by epithelialgeometry and permeabilities are considerable.We need to understand the fundamentals of fluidtransport and to agree on universal principles toestablish etiologies of the many disorders of thisprocess that are seen in the clinic. The remarkablecapacity of epithelia to absorb or secrete hugequantities of fluid, modify the secretion or absorp-tion rates, and alter the composition of the trans-ported fluid continues to amaze and confound us. I thank Dr. M. B. Burg for his insightful comments and crit-icisms and Drs. O. N. Kovbasnjuk and M. L. Barnard for crit-ically reading the manuscript.