SUBMANDIBULAR ENZYMATIC VASOCONSTRICTOR MESSENGER-RNA IN RAT-KIDNEY

Recently, we reported the isolation and identification of a potent vasoconstrictor enzyme from the rat submandibular gland, a member of the rat kallikrein gene family, which we named submandibular enzymatic vasoconstrictor (SEV). We studied whether messenger RNA (mRNA) for SEV is present in the kidney and isolated glomeruli, using the polymerase chain reaction assay with primers specific to the entire rat kallikrein family that would amplify a 430-bp fragment from their mRNA. As a probe we used a phosphorus-32-labeled oligonucleotide specific for SEV mRNA. A fragment of the predicted size was obtained on Southern blot for amplified renal RNA; however, no signal was obtained with glomerular RNA. To further confirm the presence of SEV mRNA in the kidney, polymerase chain reaction was repeated using primers specific to SEV mRNA that would amplify a 372-bp fragment from SEV mRNA alone. Again, a fragment of the predicted size was obtained on Southern blot after amplification of renal RNA but not RNA from the glomeruli. Southern blot of polymerase chain reaction-amplified RNA with primers that amplified the entire kallikrein gene family, using kallikrein complementary DNA that recognizes all members of the kallikrein gene family as a probe, revealed a 430-bp fragment for both renal and glomerular RNA, indicating that glomeruli contain mRNA for a member or members of the kallikrein family other than SEV. When the Southern blots were hybridized with a P-32-labeled oligonucleotide probe specific for glandular kallikrein, a fragment of the predicted size was obtained from amplified renal RNA but not glomerular RNA. The presence of mRNA for SEV suggests that it is synthesized by the kidney. Thus, at least two members of the kallikrein family of serine proteases, glandular kallikrein and SEV, are produced by the kidney. A third member of the kallikrein family may be present in glomerular cells. Besides glandular kallikrein, SEV and the glomerular enzyme may play a role in the regulation of renal function.