Slices and sacs: limitations on metabolic and functional studies in kidney cortex and intestine

While all experimental models, whether based on isolated preparations in vitro or on intact animals, possess characteristic limitations, reliance on simplified systems mandates special care. On the basis of both older and new evidence, the present review emphasizes problems associated especially with the use of renal cortical slices and everted sacs of the small intestine. Although these preparations have found renewed acceptance, the significance of results obtained is still at times interpreted without due regard for physiological reality. Sacs and slices will undoubtedly continue to prove useful in the study of biological processes, but their application must be predicated upon recognition of what information they can or cannot yield.