FIGURE 2

Localization of ¹²⁵I-labeled osteogenic protein-1 (OP-1) and bone morphogenetic protein (BMP) type II receptor mRNA in rat kidney. Rats received a single intravenous injection of 250 g/kg body weight and were killed at 10 minutes following injection (A–F). (A) Hematoxylin and eosin-stained brightfield image of a kidney midsagittal section (c, cortex; m, medulla). (B) Darkfield image of the same section with ¹²⁵I-labeled OP-1 accumulated in the cortex. (C) Enlarged cortex area from A showing glomeruli (arrowheads) and adjacent convoluted tubules. (D) Darkfield image of C, indicating accumulation of grains in glomeruli (arrows) and adjacent convoluted tubules. (E) Enlarged medulla (m) and S3 zone (s) from A. (F) Darkfield image of E, indicating accumulation of grains in epithelium of collecting ducts. For in situ hybridization, rat kidney sections of 5 to 7 m thick were cut, mounted on silinated slides, and hybridized with a BMP receptor type II probe for 18 hours at 50°C in 50% formamide, as previously described⁵. (G) Toluidine blue-stained brightfield image of a kidney midsagittal section. Abbreviations are: c, cortex; s, S3 zone; m, medulla. (H) Darkfield image of an adjacent section with mRNA transcript localized in the cortex and medulla in a similar pattern as ¹²⁵I-labeled OP-1 (magnification 5 in A, B, G, and H, and 200 in C–F).