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Title: Synthetic and partially-purified adenylate cyclase-stimulating proteins from tumors associated with humoral hypercalcemia of malignancy inhibit phosphate transport in a PTH-responsive renal cell line. Author: Sartori L, Weir EC, Stewart AF, Broadus AE, Mangin M, Barrett PQ, Insogna KL. Journal: J Clin Endocrinol Metab; 1988 Feb; 66(2):459-61. PubMed ID: 3339117. Abstract: Hypophosphatemia and hyperphosphaturia characteristically occur in patients with humoral hypercalcemia of malignancy (HHM). To determine if a tumor product causes these abnormalities in phosphate metabolism, rather than, for example, hypercalcemia, we investigated the effect of partially-purified adenylate cyclase-stimulating activity (ACSA) from human and animal HHM-associated tumors on sodium-dependent phosphate transport (Na PiT) in a PTH-responsive renal epithelial cell line. Thirty minute exposure to 7 X 10(-10) MbPTH (1-34) equivalents of ACSA from the human and animal tumors, reduced NaPiT by 20% and 14%, respectively. We also recently isolated an adenylate cyclase-stimulating protein (hACSP) from two human tumors associated with HHM and identified a cDNA clone for this protein which encodes a 141 amino-acid peptide. Based on the deduced amino-acid sequence, we synthesized tyr36 (1-36) hACSP. This synthetic peptide induced a 22% decrease in the initial rate of NaPiT by the epithelial monolayer. Its inhibitory activity was roughly equipotent to that of bPTH (1-34). We conclude that the ACSP derived from HHM-associated tumors decreases phosphate transport in renal epithelial cells. This peptide appears to play a key role in mediating the changes in phosphate metabolism in this syndrome.[Abstract] [Full Text] [Related] [New Search]