Different localization of spermidine/spermine N1-acetyltransferase and ornithine decarboxylase transcripts in the rat kidney.

In situ hybridization histochemistry of transverse sections from male rat kidney showed that the mRNA of the regulatory enzyme of polyamine degradation, spermidine/spermine N1-acetyltransferase, has a spotty distribution in the cortex, is low and diffused in the outer stripe and high and diffused in the inner stripe of the outer medulla. At the cellular level, this mRNA is solely expressed by the epithelium of the distal straight and convoluted nephron tubules. Since biosynthetic ornithine decarboxylase mRNA is solely found in the proximal straight tubules, it is proposed that polyamine biosynthesis and degradation occur at separate sites along the nephron.