1999 Volume 126 Issue 3 Pages 485-493
It has been reported that the urinary excretion of N-acetyl-β-D-glucosaminidase (NAG), a lysosomal enzyme, transiently increases in human after treatment with human parathyroid hormone (hPTH) (1-34). We report here that hPTH (1-34) caused transient changes in the size and density of rat renal lysosomes following urinary excretion of NAG and other lysosomal enzymes tested. Percoll density gradient centrifugation revealed that hPTH (1-34) slightly but significantly increased the fraction of high density lysosomes (around 1.12 g/ml) 5-10 min after the treatment with hPTH (1-34), with a concomitant decrease in the fraction of intermediate density lysosomes (1.07-1.08 g/ml). On electron micrographs, some lysosomes in proximal tubules but not in distal tubules showed a change in morphology from circular to oval, and became enlarged and electron-dense 5-10 min after the treatment with hPTH (1-34). These responses to bPTH (1-34) were also reversible and transient. NAG excreted in urine after treatment with hPTH (1-34) had the molecular mass of a mature form in lysosomes and/or endosomes and was not a prepro- and/or pro-form of the enzyme. Thus, the changes in the density and size of renal lysosomes appear to be associated with the exocytosis of lysosomal enzymes by hPTH (1-34).
