Letter to the Editor: On the Mechanisms of Biliary Flux.

Vartak et al's recent publicatioin reviews their previous provocative data that water flow into the bile canaliculus is not in response to an osmotic gradient, as initially proposed by Sperber. However their technique, photoactivation of a non-fluorescent precursor of fluorescein, has not been validated. In contrast, a similar technique, enzymatic activation of a non-fluorescent precursor of fluorescein supported the concept of osmotically generated canalicular water flow and confirmed that peristalsis also participates in the flow of fluid from the canaliculi into the duct system as originally described by Philips.