Rare renal transcription of the atrial natriuretic factor gene in rats. Demonstration by polymerase chain reaction

Renal synthesis of a peptide homologous to atrial natriuretic factor (ANF) has been demonstrated. The aim of the present study was to determine if transcription of the ANF gene occurs in the kidney. Rat renal RNA was extracted from whole kidneys, and, separately, from the cortex and outer and inner medulla of rat kidneys. Probing with rat ANF-cDNA did not reveal a detectable message in Northern blot analysis, even when large quantities of RNA were used at low stringency hybridization conditions. Therefore, reverse transcription (RT) followed by 35 cycles of polymerase chain reaction (PCR) was used to search for the renal message for ANF. Two 21-mer primers encompassing the 450 base pairs (bp) of the coding region of the gene were used. Each cycle consisted of annealing at 56 degrees C, extension at 72 degrees C, and denaturation at 94 degrees C. The PCR product was proven to be identical to the ANF gene by high stringency hybridization, which revealed the expected 450-bp hybrid band. Furthermore, the sequence of this product was identical to that of the coding region of the ANF gene. We used an RNA-specific PCR to obtain this band as a single reaction product. We conclude that the transcript of the ANF gene exists in the kidney, at extremely low levels. The low abundance of the RNA message raises major concerns about its physiologic relevance. Direct evidence for the translation of this transcript, and its quantification and localization, is still required to determine its significance.