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This refines a single-transporter model without proving every calcification pathway requires transport.\nexposure: Mouse CKD plus dietary phosphate loading; PiT2 knockdown or expression rescue\nevidence_span: {\"source_cache\": \"artifacts/phosphorus-research/23968976.abstract.txt\", \"locator\": \"Primary indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"6704ac0400a286d5137384f4339dd6dffb0061a41a121b6c72a0b23353cbc6f9\", \"start_char\": 0, \"end_char\": 1852, \"text_sha256\": \"6704ac0400a286d5137384f4339dd6dffb0061a41a121b6c72a0b23353cbc6f9\"}\n[phosphorus-p23968976] Sodium-dependent phosphate cotransporters and phosphate-induced calcification of vascular smooth muscle cells: redundant roles for PiT-1 and PiT-2. 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