Characteristics of rat pancreatic zymogen granules prepared by different methods

Zymogen granules isolated from tissue homogenates by differential centrifugation in isotonic sucrose solutions show substantial release of digestive enzyme when suspended in isotonic NaCl and in sucrose solutions at pH values above neutrality. A recent study reported a new method for isolating granules, involving the use of a complex homogenization medium and a Percoll gradient that was claimed to produce "stable" granules, i.e., granules that do not release their content in salt solutions and at pH values at or above neutrality. In the present study, we compare granules prepared in both ways, particularly in terms of their tendency to release amylase in isotonic ionic solutions and as a function of pH. The relative absence of amylase release from granules isolated by the new technique was found to be attributable to simple differences in the details of the experimental procedures that were used and not to actual differences in the characteristics of the two granule preparations. For example, previous studies with granules prepared in sucrose solutions reported substantial salt-induced release at 37 degrees C, whereas the recent study reporting the absence of salt-induced release from granules obtained from a Percoll gradient was done at 24 degrees C. Under the identical experimental conditions as used in the present study, little amylase release was seen at 24 degrees C for granules isolated by either technique, but substantial release was seen for both at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)