Human kidney sections exhibiting TPO mRNA expression. Kidney sections of individuals with normal platelet counts, probed with TPO cDNA probe (A), TPO oligonucleotide probe (B), and the sense strand of the TPO mRNA as a negative control (D). Kidney section of a thrombocytopenic patient probed with TPO cDNA probe (C). Strong hybridization signal in proximal convoluted tubules (Prox) and less consistent staining in the distal convoluted tubules (Dist). Peritubular cells (PT) and endothelial cells (En) remain negative. Original magnifications: (A, B, and C) ×396; (D) ×240.