Figure 5. ELISA measurements of cGMP content of epiphyses of tibias from wild type newborn mice.

Tibias were collected and cultured as described for the cGi500 measurements. The proximal epiphyses were then slit to expose the growth plate (see Figure 3A) and the slit tibias were preincubated in a well of medium containing 1 µg/ml heparin with or without FGF-18 (0.5 μg/ml) for 80 min. After the preincubation ± FGF, the epiphysis regions were cut off and prepared for cGMP ELISA measurement as described in the Materials and Methods. Where indicated, the preincubation ±FGF was followed by a 15 min incubation in the same medium, but also including 100 nM CNP, mimicking the conditions used for the cGi500 measurements. (A) cGMP content of the epiphyses normalized to protein content. The graph shows the mean ±s.e.m. of measurements from three separate experiments. (B) The values from A for the no added CNP condition are replotted with an expanded y-axis. Data were analyzed by unpaired t-tests, with the Holm-Sidak correction for multiple comparisons. **p≤0.01.