Immunoreactivity of PTH-binding in intact bovine kidney tissue and cultured cortical kidney cells indicative for specific receptors.

Localization of PTH-binding sites has been examined in intact kidney sections and cultured cells derived from bovine kidney cortex. Tissue sections were incubated with 10(-7) M bovine PTH (1-84) for 2 h, cells for 15 min, at 37 degrees C. Visualization of PTH-binding was achieved by immunocytochemistry using a carboxy-terminal specific anti-PTH antiserum (S 478). For control, cell culture incubations were performed applying competitively 10(-7) bovine PTH (1-84) and a 10-fold excess of synthetic 1-34 PTH fragment, not antigenic for S 478. This resulted in a lack of staining. PTH-binding was found in all cells of the proximal and the distal tubule, and with less intensity in the thick ascending limb of Henle's loop. In collecting ducts a PTH specific staining was also present, which was confined to single cells localized between others without PTH binding sites. No staining was seen in glomerula, the thin limb of Henle's loop, in blood vessels, and in connective tissue. The data suggest that large parts of the nephron contain PTH-binding sites, although in different amounts. This is in agreement with the numerous actions of PTH in the kidney. In the collecting segment a distinct cell-to-cell difference was disclosed indicative for different functional states or cellular heterogeneity.