Abstract
Calcium-sensing receptors (CaSR) are present in many cells, and sense and translate micro molar changes in extracellular calcium into intracellular signals, including parallel changes in intracellular calcium. In the juxtaglomerular (JG) cell, increased intracellular calcium suppresses the calcium-inhibitable adenylyl cyclase type-V (AC-V), reducing cAMP and inhibiting renin release. We hypothesized that JG cells express CaSR, and changes in AC-V activity and renin release might be mediated by activation of CaSR. We used primary cultures of isolated mouse JG cells. RT-PCR on total RNA extracted from JG cells was run 40 cycles with CaSR-specific primers, giving a positive band at 151 bp, consistent with CaSR. Next, in JG cells, immunofluorescent labeling by an antibody specific for CaSR showed significant fluorescence compared to negative controls (0 vs. 167± 8.5 AU, p<0.001) Finally, treating primary cultures of isolated JG cells with the calcium sensing receptor agonist Cinacalcet (Amgen) at 50 and 1000 nM to stimulate the CaSR in the presence of IBMX decreased cAMP to 85.8±27.2% and 79.1±12.7% of basal, respectively, and decreased renin release from 450.1±81.7 to 350.2±83.8 and 222.6±56.2 ng ANGI/ml/hr/mg protein (p<0.01), respectively. We conclude that the CaSR is expressed in JG cells and these CaSR mediate changes in cAMP formation and renin release from JG cells (NIH RO-1 HL076469).
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