The effect of Met-enkephalin on mice liver lysosomes.

The unsedimentable activities of acid phosphatase (AP) and beta-glucosidase (BG), from mice liver lysosomes significantly increased 6 h after a single i/p injection of Met-enkephalin (MENK). The activity of AP in the serum at the same time remained unchanged. Multiple injections of MENK (8 x 10 mg/kg) induced a significant decrease in AP activity in the serum and no change in the unsedimentable activities of AP or BG. MENK did not elicit any significant extracellular release of lactate dehydrogenase (LDH) either, indicating that, under the experimental conditions described, the cells remained intact. Other parameters, such as the activities of AP and BG in the liver and total sialic acid content in the serum and spleen remained unaltered. Moreover, MENK in concentrations of 10(-12) M, 10(-8) M, 10(-6) M or 10(-4) M did not change the activities of the lysosomal enzyme markers AP or BG in vitro. These data indicate far less pronounced transient effects of MENK on lysosomal membranes and enzymes compared to Leu-enkephalin which may be relevant for the use of MENK in combined chemo-immunotherapy.