Expression of somatostatin and somatostatin receptor subtypes 1-5 in human normal and diseased kidney

Somatostatin mediates inhibitory functions through five G protein-coupled somatostatin receptors (sst(1-5)). We used immunohistochemistry, immunofluorescence, and RT-PCR to determine the presence of somatostatin receptors sst(1), sst(2A), sst(2B), sst(3), sst(4), and sst(5) in normal and IgA nephropathy human kidney. All somatostatin receptors were detected in the thin tubules (di5tal convoluted tubules and loops of Henle) and thick tubules (proximal convoluted tubules) in the tissue sections from nephrectomy and biopsy samples. Immunopositive sst(1) and sst(4) staining was more condensed in the cytoplasm of tubular epithelial cells. In normal kidney tissue sections, podocytes and mesangial cells in the glomeruli stained for sst(1), sst(2B), sst(4) and sst(5), and stained weakly for sst(3). In IgA kidney tissue, the expression of somatostatin receptors was significantly increased with particular immmuno-positive staining for sst(1), sst(2B), sst(4), and sst(5) within glomeruli. In the epithelial cells, the staining for sst(2B) and sst(4) in proximal tubules and sst(1), sst(2B), and sst(5) in distal tubules was increased. The mRNA expression of sst(1-5) was also detected by RT-PCR. Somatostatin and all five receptor subtypes were ubiquitously distributed in normal kidney and IgA nephropathy. The increased expression of somatostatin receptors in IgA nephropathy kidney might be the potential pathogenesis of inflammatory renal disease.