Serum lipids and latent coronary insufficiency

Abstract

Dipeptidyl aminopeptidase II (DAP II) was demonstrated cytochemically in macrophages harvested from the peritoneal cavity of rats given i.p. injections of phosphate-buffered saline alone or containing colloidal gold or chloroquine, with fetal calf serum or with saline containing heat-killed bacteria. Smears stained for DAP II disclosed red staining in numerous granules in most of the macrophages. Highly electron-dense foci demonstrative of DAP II reactivity were observed at the ultrastructural level in many but not all of the cytoplasmic dense bodies that constituted secondary lysosomes or heterophagosomes and in numerous small vesicles in the macrophage cytoplasm. Densified foci in nuclear envelope and rough endoplasmic reticulum were indicative of highly localized DAP II activity. Golgi cisternae lacked reaction product, however. These localizations suggested a unique pathway entailing synthesis of DAP in foci of the nuclear envelope and cytoplasmic granular reticulum and transport by vesicles directly to cytoplasmic granules and possibly to other organelles. Monocytes of rat bone marrow and buffy coat were devoid of reaction product, as were other leukocytes. Bone marrow macrophages contained lysosomes with DAP II reaction product. The DAP II contained in a lysosome-rich preparation obtained by the subcellular fractionation of peritoneal wash cells was biochemically characterized as a typical DAP II in terms of its structural latency, substrate specificity, inhibitor sensitivities, pH and activator requirements. Unlike most other lysosomal peptide hydrolases, DAP II exhibited the properties of an active-serine exopeptidase whose hydrolytic activity included the cleavage of prolyl bonds.