Parathyroid hormone-activated phosphoinositide degradation and calcium channels in human dermal fibroblasts

Previous studies have shown that there are two types of parathyroid hormone (PTH) receptors on human dermal fibroblasts. We evaluate the effects of PTH on intracellular cyclic AMP, calcium and phosphoinositides in order to define the effector systems of the PTH receptors. The results show that PTH stimulates cyclic AMP accumulation in the human dermal fibroblasts with half-maximal effect at 1-5 nM. PTH also increases intracellular calcium as measured by the technique using Fura-2 fluorescent dye and stimulates phosphoinositide degradation as evaluated by column chromatography. The half-maximal effect on AMP occurred at 5 nM, while those effect on calcium and phosphoinositide turnover occurred at 500 nM of PTH. The results show that cyclic AMP, intracellular calcium and phosphoinositides are second messengers for PTH in human dermal fibroblasts. These results provide further evidence to support the concept of heterogeneity of the PTH receptor and its effector system.