Figure 4.

PTH regulation of chimeric NaPi cotransporters. OK cells were transfected with wt mIIa or mIIb cotransporters or with the chimeras mIIaN-mIIb, IIbN-IIa, IIa-IIbCT, and IIb-IIaCT (see Fig. 1) and processed for PTH experiment (see Materials and Methods). Cells were incubated for 2 h with 10⁻⁸ M 1–34 PTH, and the patterns of green fluorescent cells before (Upper) and after (Lower) the treatment were compared. Down-regulation of mIIa, mIIbN-mIIa, and mIIa-mIIbCT by 1–34 PTH is indicated by the disappearance of their specific “patches.” Results are representative of 4 to10 independent experiments.