The release of intralysosomally-stored 125I-Triton WR-1339 and lysosomal enzymes from the isolated perfused rat liver in the presence and absence of cytochalasin B.

The effect of in vivo loading of the lysosomotropic agent 125I-Triton WR-1339 on the release of lysosomal enzymes in isolated perfused rat liver has been studied in the presence and absence of the microfilament poison cytochalasin B, as has the release of the 125I-Triton WR-1339 itself. Perfused isolated rat livers released all the enzymes studied (arylsulphatase, beta-galactosidase and lactate dehydrogenase) and, when preloaded, 125I-Triton WR-1339 was also released into the perfusate. The magnitude of the net release (after 5 hr perfusion) was in the order beta-galactosidase = 125I-Triton WR-1339 greater than lactate dehydrogenase greater than arylsulphatase. Preloading of the lysosomes with the detergent appeared to bring about an increase in the release of all the enzymes studied (3.5 X for beta-galactosidase, 2.6 X for arylsulphatase and 1.7 X for lactate dehydrogenase). The addition of the microfilament poison cytochalasin B into the perfusate of non-loaded livers significantly increased the release of the lysosomal enzymes but not that of lactate dehydrogenase. However in the 125I-Triton WR-1339- loaded livers cytochalasin B had no effect on the release of lysosomal enzymes or detergent, but reduced the loss of lactate dehydrogenase by about 50%. This failure of cytochalasin B to potentiate the exocytosis of lysosomal contents in 125I-Triton WR-1339-loaded livers is similar to the effect found previously with 125I-PVP-loaded livers and may be related to the already enhanced loss of lysosomal enzymes apparently caused by the loading.