Fig. 3.

Actions of PTH ligands in vivo. Peptide ligands or vehicle were injected i.v. into C57/BL6 mice for (A–C) acute time course analyses or (D) two-week bone-metabolic studies. Acute studies were performed with hPTH(1–34), M-PTH(1–28), and M-PTH(1–34) (20 nmol/kg), and vehicle control. Blood withdrawn immediately prior to injection (t = 0) and at times thereafter was assessed for (A) ionized calcium, (B) inorganic phosphate, or (C) PTH analog content. Analog content was determined by treating HEK-293 cells transiently transfected with the hPTHR with 1 μl of plasma for 30 min in the presence of IBMX and then measuring intracellular cAMP. C Inset shows that the peptides, when measured directly, are approximately equipotent in the HEK-293/hPTHR cell assay; no cAMP response was detected for the plasma samples in mock-transfected HEK-293 cells (not shown). The data show means (± SEM) of values from a single experiment in which (A) five, (B) six, or (C) three mice were used per group. For each analysis, similar results were obtained in at least two other experiments. Two-week daily injection studies were performed with rPTH(1–34) and M-PTH(1–34) (5 nmol/kg per day; n = 7 per group) in D. At the two-week end-point, femurs and tibiae were isolated and imaged by μCT (panes 1–6) or histology with von Kossa staining (panes 7–9). Shown are transverse views of the distal, metaphyseal (panes 1–3) and mid-diaphyseal (panes 4–6) regions of the femurs, and sagittal views of proximal tibiae (panes 7–9). (Magnification: D, 7–9, 40×.)