Figure 3. Relationship between calcitriol and GDNF signaling.

The beneficial effect of calcitriol addition to media was shown to be a result of increased GDNF. (A, B) 10 nM calcitriol added to media caused almost a 1.8-fold increase in GDNF expression, observed by Western blotting. GAPDH was used as loading control; lanes:+with calcitriol, - control; *p<0.05. In the presence of 0.3 U heparinase III, the number of dopamine neurons observed was significantly decreased regardless of calcitriol incorporation (C). Bars represent percentage tyrosine hydroxylase immunoreactive neurons as a percentage of total cells±SEM. ***p<0.001, **p<0.01. Representative images of primary ventral mesencephalic cultures supplemented with 0.3 U heparinase III without calcitriol (D) and with the addition of 10 nM calcitriol (E). Cultures were stained with tyrosine hydroxylase (red) and β-III tubulin (green). Scale bar: 20 µm.