P2Y receptors present in the native and isolated rat glomerulus

Area of Science:

• Nephrology
• Molecular Biology
• Pharmacology

Background:

• Extracellular ATP (adenosine triphosphate) is known to mobilize intracellular calcium in rat glomeruli via P2Y receptors.
• The specific subtypes of P2Y receptors involved in this process within the glomerulus have not been previously identified.

Purpose of the Study:

• To identify the specific P2Y receptor subtypes expressed in rat glomeruli.
• To functionally characterize these receptors and investigate the potential role of intra-renal sympathetic nerve terminals in providing extracellular ATP.

Main Methods:

• Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect P2Y receptor subtype mRNAs.
• Functional receptor expression was assessed by measuring inositol phosphate pathway stimulation using selective agonists.
• Immunohistochemistry with polyclonal antibodies was employed to confirm protein expression of P2Y receptors.
• In vivo experiments involved sympathectomy using 6-hydroxydopamine to assess the contribution of sympathetic nerves to extracellular ATP signaling.

Main Results:

• mRNA for P2Y1, P2Y2, P2Y4, and P2Y6 receptors were detected in rat glomeruli.
• Functional studies confirmed the expression of P2Y1 and P2Y2/P2Y4 receptors, but not P2Y6.
• P2Y1 and P2Y2 receptor proteins were localized in mesangial cells and podocytes, respectively.
• Sympathectomy did not alter ATP-induced inositol phosphate production, suggesting intra-renal sympathetic nerves are not a primary source of extracellular ATP in this context.

Conclusions:

• Rat glomeruli express mRNAs for multiple P2Y receptor subtypes, with functional evidence for P2Y1 and P2Y2/P2Y4 receptors.
• P2Y1 and P2Y2 receptors are present in specific glomerular cell types (mesangial cells and podocytes).
• Intra-renal sympathetic nerve terminals do not appear to be a significant source of extracellular ATP involved in glomerular signaling.