Itoh K, Nonoguchi H, Shiraishi N, Tomita K
Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Japan.
Exp Nephrol. 1999 Jul-Aug;7(4):328-36. doi: 10.1159/000020621.
Atrial natriuretic peptide (ANP) has three types of receptor. We investigated the gene regulation of three types of ANP receptors (ANPR-A, B, and C) in rat glomeruli using reverse transcription coupled with competitive polymerase chain reaction (PCR).
Competitive PCR revealed that ANPR-C mRNA expression was most abundant (ANPR-C > A >> B) in glomeruli from control rats among mRNA expressions of three receptors, which were 20- to 15,000-fold higher than those in inner medullary collecting ducts. Two days' dehydration caused reversible decreases of ANPR-A, B, and C mRNAs by 50-80%. To determine the mechanisms of down-regulation of mRNA expression, isolated glomeruli were incubated in isotonic or hypertonic solution. Hyperosmolality induced by NaCl, mannitol or raffinose caused significant increases of ANPR-A, B, and C mRNA expression. Hypertonicity by urea showed smaller effects. ANP stimulated the expression of ANPR-A, B, and C mRNA in vitro.
These results indicate that dehydration caused reversible decreases of ANPR-A, B, and C mRNA expression in glomeruli, and these decreases were not caused by increased plasma osmolality but probably by lower circulating levels of ANP.
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