... cells. The vacuolar H+-ATPase inhibitor bafilomycin and the cathepsin D inhibitor pepstatin A partially inhibited, both in vivo and in vitro, the cAMP response to choleratoxin. This cathepsin ... intraperi-toneal injection of either pepstatin A, an inhibitor of aspartic acid proteases [17], or a mixture of bafilo-mycin A1 and folimycin, two inhibitors of the vacuolarATPases [16], prior to CT administration ... comparablyinhibited generation of the CT -A1 peptide. In rat liver,chloroquine accumulates in hepatic endosomes, leadingto an increase in the lag phase for activation of adeny-late cyclase by...