Microperoxisomes and catalase peroxidatic activity in the pancreas of two amphibian species (Salamandra salamandra L. and Rana esculenta L.).

The fine structure of microperoxisomes (anucleoid peroxisomes) and catalase peroxidatic activity in salamander and frog pancreas have been investigated following glutaraldehyde fixation and incubation in a modified NOVIKOFF-GOLDFISCHER alkaline DAB-medium. Reactive microperoxisomes ranging in diameter from 0.16 to 0.76 micrometer were identified in both exocrine (acinar and ductular centro-acinar cells) and insular (B-, A-, D-cells) pancreatic tissue, as well as in the nerve fibers and endings. Their incidence was considerably higher in the exocrine parenchyma, where sometimes in frog they accumulated in clusters. Individual microperoxisomes showed close spatial relationship and occasionally membrane continuities with smooth surfaced endoplasmic reticulum and zymogen granules. They were also localized in the proximity or in direct contact with the nuclear envelope, mitochondria, GOLGI condensing vacuoles, lipid inclusions and plasma membrane. The morphological findings support the microperoxisomes origin from the agranular endoplasmic reticulum and their possible discharge into the extracellular spaces through an exocytosis-like mechanism. The cytochemical observations are discussed in relation with the concepts on catalase biosynthesis and peroxisomes functional significance.