In vitro evaluation of a bioartificial pancreas under various hemodynamic conditions.

A bioartificial pancreas in which isolated islets of Langerhans are placed between two polyacrylonitrile membranes, blood circulating successively above the upper and below the lower membranes following a U-shaped circuit, has been developed. The two parts are connected by an outer loop consisting of a thin tubing. The length of this tubing determines the magnitude of the flow rate of blood through the device. The aim of this work was to determine experimentally the optimal configuration of the system containing isolated rat islets and a Krebs buffer circulating through the device. The amount of insulin released by the bioartificial pancreas was determined during a 20-mM square-wave glucose stimulation. First, the inlet pressure was set at 100 mm Hg, and the effect of the length of the tubing was investigated with two devices perfused simultaneously. For a short tubing (flow rate, 20 ml/min), a sharp increase in insulin release in response to glucose was observed; it increased within 4 min from 217 +/- 50 to 761 +/- 237 microU/500 islets/min (p less than 0.05), the peak value being reached at 11 +/- 2 min following the beginning of the stimulation. For a long tubing (flow rate, 3 ml/min), the increase in insulin release was more sluggish. It increased from 133 +/- 53 to 222 +/- 43 microU/500 islets/min at 4 min, the peak value being reached only at 20 +/- 3 min. These data are consistent with a more efficient diffusional transfer of insulin in the case of the high circulating flow.(ABSTRACT TRUNCATED AT 250 WORDS)