Acute salinity and temperature challenges during early development of zebrafish: Differential gene expression of PTHs, PTHrPs and their receptors

Parathyroid hormone (pth), parathyroid hormone-related peptide (pthrp) and their receptors are involved in the regulation of calcium homeostasis in all vertebrates. To further understand the role of these genes in teleosts during development, we investigated the expression pattern of pth1, pth2, pthrp1, pthrp2, and their receptors pth1r, pth2r, pth3r, and their response to acute salinity and temperature challenge during early development of zebrafish, Danio rerio. The results revealed that pth1, pth2, pthrp1, pthrp2, pth1r, pth2r, pth3r were differentially expressed during early development, and pth1, pthrp1, pth1r, pth2r mRNA were detected from 0 hpf. pth2 and pth3r mRNA were detected after fertilization. Exposure of zebrafish embryos and larvae to acute osmotic (30) stress for 15 min failed to modify the expression levels of pthrp2 mRNA from levels in control fish. However, salinity challenge significantly (P < 0.01) modified pth1, pth2, pth3r at 3 dpf, pthrp1 (P < 0.01) and pth1r (P < 0.05) were both significantly modified at 5 dpf, and pth2r was significantly (P < 0.01) modified at 4 dpf and 5 dpf. Exposure of embryos and larvae to a cold (18 °C) stress generally up-regulated mRNA levels of pth1, pth2, pthrp1, pthrp2 and pth3r from 2 dpf to 5 dpf, while a hot (38 °C) stress generally down-regulated mRNA levels of these genes. After acute temperature challenge, expression levels of pth receptors were greatly influenced except pth2r. The results indicate that the contribution of pth1, pth2, pthrp1, pthrp2, pth1r, pth2r and pth3r genes to the stress response in zebrafish may be stressor-specific during early development. Overall, the results from this study provide a basis for further research into the developmental and stressor-specific role of pth1, pth2, pthrp1, pthrp2, pth1r, pth2r and pth3r in zebrafish