Isolation and characterization of crinosomes--a subclass of secondary lysosomes

A technique is presented for isolating a subclass of lysosomes, designated crinosomes, by one-step floating-up centrifugation in a cesium-containing sucrose gradient. Rats were treated with vinblastine in order to induce the formation of crinosomes. Vinblastine blocked exocytosis of secretory granules at the cell border. Later on, lipoprotein-containing granules were seen throughout the cytoplasm. Immunolabeling with polyclonal antibodies against albumin demonstrated a severalfold greater presence of gold particles over crinosomes and Golgi cisternae than over the surrounding organelles. The induction of crinosomes by vinblastine made it possible to isolate thenm on a sucrose gradient. These organelles contained marker enzymes for the Golgi complex (galactosyl transferase) and lysosomes (cathepsins). The purity of the fraction was high. The crinosomes were proteolytically and lipolytically very active. The crinosomes were positive to cytochemical acid phosphatase staining. It is concluded that crinosomes develop from fusion between lysosomes and secretory granules and that they are active in degrading retained secretory material.