Factors influencing the isolation process of islets of Langerhans.

Determination of collagenase and proteolytic activities and slabgel electrophoresis of collagenase preparations obtained from different suppliers reveals a highly variable content of collagenase, proteolytic activities and other components. The electrophoresis pattern can help to select collagenase preparations with a low content of impurities suitable for islet isolation. During islet isolation the exocrine tissue releases large amounts of proteolytic activities into the digestion medium, which decreases islet yield. Addition of 10% albumin to the digestion medium strongly suppresses the release of proteolytic activity and increases the number of islets obtained. Addition of both albumin and trypsin inhibitors further increases not only the number of islets, but also the total volume of islet tissue obtained. The islet isolation process is not critically dependent on the pH in the range 6.2 to 8.0 and only marginally dependent on the calcium concentration.