Expression of adrenergic and cholinergic receptors in murine renal intercalated cells.

Neurons influence renal function and help to regulate fluid homeostasis, blood pressure and ion excretion. Intercalated cells (ICCs) are distributed throughout the renal collecting ducts and help regulate acid/base equilibration. Because ICCs are located among principal cells, it has been difficult to determine the effects that efferent nerve fibers have on this cell population. In this study, we examined the expression of neurotransmitter receptors on the murine renal epithelial M-1 cell line. We found that M-1 cells express a2 and b2 adrenergic receptor mRNA and the b2 receptor protein. Further, b2 receptor-positive cells in the murine cortical collecting ducts also express AQP6, indicating that these cells are ICCs. M-1 cells were found to express m1, m4 and m5 muscarinic receptor mRNAs and the ml receptor protein. Cells in the collecting ducts also express the ml receptor protein, and some m1-positive cells express AQP6. Acetylcholinesterase was detected in cortical collecting duct cells. Interestingly, acetylcholinesterase-positive cells neighbored AQP6-positive cells, suggesting that principal cells may regulate the availability of acetylcholine. In conclusion, our data suggest that ICCs in murine renal collecting ducts may be regulated by the adrenergic and cholinergic systems.