Skin-derived fibroblasts respond to human parathyroid hormone-like adenylate cyclase-stimulating proteins

Human tumors and keratinocyte-conditioned medium contain PTH-like adenylate cyclase-stimulating proteins. Human dermal fibroblasts have receptors that recognize PTH and a factor associated with humoral hypercalcemia of malignancy in rats. We examined 10 human dermal fibroblast lines for an adenylate cyclase response to PTH. Six of 10 lines tested displayed a definite response (2.4- to 3.8-fold over basal) to 10^-6 m bovine PTH-(1-34). This response was inhibited by the PTH analog and antagonist Nle^8,18, Tyr³⁴-bPTH-(3-34). We also examined whether human dermal fibroblasts are capable of responding to either a human PTH-like tumor-derived factor or the PTH-like factor contained in human keratinocyte-conditioned medium. Both human humoral hypercalcemia of malignancy-associated tumor extract (2.5 × 10^-10 m) and keratinocyte-conditioned medium (8 × 10^-10 m) stimulated human dermal fibroblast adenylate cyclase. These concentrations are markedly lower than those required for PTH-induced ade-nylate cyclase stimulation. This activity was also inhibited by the PTH analog. The high prevalence of PTH-responsive adenylate cyclase in dermal fibroblast lines and the apparent potency of tumor-derived and keratinocyte-derived PTH-like factors in dermal fibroblasts suggest that these factors may play a role in normal dermal physiology.