Effects of colchicine on acid hydrolase secretion by cultured mouse peritoneal macrophages
Thyberg, J.; Hellgren, D.; Blomgren, K.
European Journal of Cell Biology 26(1): 168-176
1981
ISSN/ISBN: 0171-9335 PMID: 7327178 Document Number: 181683
Thioglycollate-elicited mouse peritoneal macrophages were cultured in vitro and the secretion of lysozyme, .beta.-glucuronidase and .beta.-N-acetylglucosaminidase was studied. In 48 h the cells released more than their content of lysozyme and .apprx. 1/3 their content of the 2 acid hydrolases into the culture medium. No comparable release of lactate dehydrogenase was noted. The intracellular enzyme levels remained constant. Colchicine partially inhibited the overall accumulation of lysozyme, but the fraction of the total activity appearing in the medium did not change. The production of lysozyme was disturbed, but not its secretion. Colchicine left the cellular levels of the acid hydrolases unaffected, whereas the extracellular accumulation of the enzymes was enhanced. Exposure of the macrophages to zymosan particles markedly stimulated the secretion of the acid hydrolases without affecting the release of lysozyme and lactate dehydrogenase. Cells allowed to ingest horseradish peroxidase (HRP) prior to exposure to zymosan released the exogenous tracer in parallel with the acid hydrolases. Colchicine inhibited phagocytosis of zymosan slightly enhanced secretion of the acid hydrolases, but did not appreciably affect the release of HRP. The acid hydrolases were primarily released from secondary lysosomes. In view of the colchicine results, it is uncertain whether the secondary lysosome compartment labeled by HRP was the sole source of zymosan-induced acid hydrolase secretion. Fine structurally, colchicine caused a complete disappearance of cytoplasmic microtubules as well as a characteristic organelle redistribution. The dictyosomes of the Golgi complex and the lysosomes were spread from a circumscribed juxtanuclear area throughout the cytoplasm. A more peripheral distribution of the lysosomes and a slowed down formation of endocytic vesicles and phagosomes might explain the stimulatory effect of colchcine on basal and zymosan-induced acid hydrolase secretion. Since colchicine inhibits endocytosis, there is no direct coupling between this process and acid hydrolase secretion. If the latter enzymes are mainly of lysosomal origin, the lysosomes may not have a major responsibility for returning membrane internalized by endocytosis back to the cell surface.