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Expression of mRNA for natriuretic peptide receptor subtypes in bovine kidney
1Institute of Nephrology, Niigata University School of Medicine, Japan.
Abstract:
The localization of mRNA for atrial natriuretic peptide (ANP) receptor subtypes (A, B, C) in the kidney was examined. Quantitative analysis of the ribonuclease protection assay showed that the numbers of type A receptor (ANPRA) mRNA were 6.9 x 10(7) in the glomeruli and 10.4 x 10(7) molecules/micrograms of total RNA in the inner medulla, and that of type C receptor (ANPRC) mRNA was 21.7 x 10(7) molecules/micrograms of total RNA in the glomeruli. The type B receptor (ANPRB) mRNA was present in smaller numbers (4.5-4.9 x 10(6) molecules/micrograms of total RNA) evenly throughout the kidney fractions. In situ hybridization demonstrated both ANPRA and ANPRC mRNA selectively in the glomerular epithelial cells and ANPRA mRNA in the collecting duct cells of the inner medulla. ANPRC was also localized on the foot processes of glomerular epithelial cells by immunohistochemistry using a specific antibody against the receptor. These results indicate that ANPRA is the major biologically active receptor for the ANP family of hormones in the kidney and is present selectively on the glomerular epithelial cells and inner medullary collecting duct cells. These cells are presumed to play a role in the regulation of glomerular filtration rate and sodium excretion induced by the family of ANP.
Insights
Atrial natriuretic peptide (ANP) receptors A and C are primarily located in kidney glomeruli and inner medulla. These receptors are crucial for regulating glomerular filtration and sodium excretion.
Area of Science:
- Nephrology
- Molecular Biology
- Endocrinology
Background:
- Atrial natriuretic peptide (ANP) plays a vital role in regulating blood pressure and fluid balance.
- Understanding the localization of ANP receptor subtypes in the kidney is crucial for elucidating ANP's physiological effects.
Purpose of the Study:
- To investigate the precise localization and abundance of atrial natriuretic peptide (ANP) receptor subtypes A, B, and C (ANPRA, ANPRB, ANPRC) mRNA and protein within the kidney.
- To determine which ANP receptor subtype is predominantly expressed and potentially responsible for ANP-mediated effects in renal tissue.
Main Methods:
- Quantitative ribonuclease protection assay (RPA) to measure mRNA levels of ANPRA, ANPRB, and ANPRC in different kidney fractions.
- In situ hybridization to visualize the cellular localization of ANPRA and ANPRC mRNA.
- Immunohistochemistry using a specific antibody to confirm the protein localization of ANPRC.
Main Results:
- ANPRA mRNA was abundant in glomeruli and inner medulla, while ANPRC mRNA was highly concentrated in glomeruli.
- ANPRB mRNA was found in lower, evenly distributed amounts across kidney fractions.
- In situ hybridization confirmed ANPRA and ANPRC mRNA in glomerular epithelial cells and ANPRA in inner medullary collecting duct cells. Immunohistochemistry localized ANPRC protein to glomerular epithelial cell foot processes.
Conclusions:
- Atrial natriuretic peptide receptor A (ANPRA) is the major biologically active receptor for ANP in the kidney.
- ANPRA is selectively expressed in glomerular epithelial cells and inner medullary collecting duct cells, suggesting their roles in regulating glomerular filtration rate and sodium excretion.
- ANPRC is also present in glomerular epithelial cells, potentially contributing to ANP signaling in the glomerulus.