A Cytochemical Study on the Pancreas of the Guinea Pig

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Abstract
Ribonucleo-protein (RNP) particles isolated by Na deoxycholate treatment from pancreatic microsomes have a ribonucleic acid (RNA) content of 35 to 45% of their dry weight. In the analytical ultracentrifuge about 85% of the material has a sedimentation coefficient of [image] 85 S. These particles contain amylase, RNase, and trypsin-activatable proteolytic activities which cannot be washed off or detached by incubation in 0.44 [image] sucrose. The enzymes are released, however, by incubation in the presence of low concentrations of adenosine triphosphate, inorganic pyrophosphate, or ethylenediamine-tetracetate, and high concentrations of inorganic phosphate and adenosine monophosphate. At the same time, and at the same concentrations,[image] 80% of the RNA and [image] 25% of the protein of the particles becomes also non-sedi-mentable. The simultaneous addition of Mg++ to the incubation medium prevents these losses. This finding, together with the observation that all the Mg++ of the particles is released by the same agents, makes it likely that Mg++ holds the particles together, and that its removal by the chelators used causes the particles to disintegrate. These findings are discussed in relation to the molecular structure of the RNP particles.