Differential expression of mRNA for guanylyl cyclase-linked endothelium-derived relaxing factor receptor subunits in rat kidney.

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Abstract
Endothelium-derived relaxing factor (EDRF) has profound effects on the renal vasculature, the glomerular mesangium, and also affects renal salt excretion. EDRF stimulates guanylyl cyclases, which are thought to be heterodimers comprised of alpha and beta subunits. Two alpha and two beta isoforms have been identified thus far. However, the molecular composition of in vivo guanylyl cyclase-linked EDRF receptors is unknown. We used polymerase chain reaction to clone a portion of the rat alpha 2 subunit. Guanylyl cyclase-linked EDRF receptor mRNA was detected in microdissected renal structures using a reverse transcription/polymerase chain reaction assay. The interlobular artery/afferent arteriole contained mRNA for the alpha 1, alpha 2, and beta 1 subunits; a faint beta 2 band was found in 29% of experiments. In contrast, the cortical collecting duct contained mRNA only for alpha 1 and beta 2 subunits. We conclude that guanylyl cyclase-linked EDRF receptor subunit isoforms are independently and heterogeneously expressed in the renal vasculature and cortical collecting duct, suggesting that several different EDRF receptors exist in vivo. These data suggest that the tubule receptor is composed of alpha 1/beta 2. The vasculature may contain at least two different EDRF receptors (alpha 1/beta 1 and alpha 2/beta 1). Some beta 2 may also be expressed, allowing for even greater heterogeneity.