Benzylpenicillin transport and subcellular distribution in mouse peritoneal macrophage monolayers

[14C]Benzylpenicillin was rapidly taken up into and eluted from mouse peritoneal macrophage monolayers and entered cytosol, lysosomes and phagolysosomes containing Staphylococcus aureus. Equilibrium concentrations in cytosol and lysosomes were consistent with transport by diffusion but partial membrane carrier dependence was evidenced by saturability (Km and Vmax 110 mM and 117 nmoles (10(6) cells)-1 (3 min)-1 respectively) and inhibition by probenecid. Partial dependence of transport on metabolic energy was shown by inhibition with cyanide plus 2-deoxyglucose and the temperature coefficient (Q10) was about 2. Some of the intralysosomal radiolabel accumulated as benzylpenicilloic acid.