Two populations of acid hydrolase-containing particles in rat epididymis

Two populations of acid hydrolase-containing particles were distinguished in homogenates of rat epididymis. One of them was rich in acid phosphatase activity, equilibrated at density 1.17 in a sucrose gradient, and it sedimented between 12,000g 2.5 min and 43,000g 60 min (light particles). The other was poor in acid phosphatase activity and rich in N-acetyl-beta-D-glucosaminidase, arylsulphatase, and beta-glucuronidase activity, equilibrated at density 1.20 in a sucrose gradient and it sedimented between 400g 2.5 min and 12,000g 2.5 min (heavy particles). 131I-albumin (RISA) injected into the lumen of the cauda was partially recovered in subcellular particles of homogenates of this region. These particles, incubated at pH 5, were able to digest the engulfed RISA. The subcellular distribution of RISA-containing particles and RISA-digesting particles was similar to that of the heavy hydrolase-containing particles. This suggests that these latter are engaged, at least in part, in heterophagic processes.