PKA and PKC signaling pathways mediate vitamin D₃-regulated intestinal phosphorus absorption in broiler chickens

Three experiments were conducted to investigate the functional roles of the protein kinase A (PKA) and protein kinase C (PKC) signaling pathways in vitamin D₃ (VD₃)-regulated intestinal phosphorus (P) absorption in broiler chickens. Experiment 1 examined the effects of dietary VD₃ levels on the PKA and PKC signaling pathways. Experiments 2 and 3 evaluated the effects of intraperitoneal injection of PKA and PKC inhibitors on intestinal P transporter expression. Results from Experiment 1 showed that 1000 IU/kg VD₃ improved growth performance (1-19 d), increased mRNA and protein expression of the jejunal NaPi-IIb phosphate transporter (P < 0.05), and affected the protein expression ratios of p-PKA/t-PKA, p-PI3K/t-PI3K, p-ERK/t-ERK, p-PKC/t-PKC and p-p38MAPK/t-p38MAPK (P < 0.05). In Experiment 2, the PKA inhibitor H-89 reduced mRNA and protein expression of jejunal NaPi-IIb in broilers (10-15 d) (P < 0.05). H-89 increased p-PI3K/t-PI3K and p-ERK/t-ERK protein expression ratios (P < 0.05), reduced the p-p38MAPK/t-p38MAPK ratio (P < 0.05), and had no effect on the p-PKC/t-PKC ratio (P > 0.05). Experiment 3 showed that the PKC inhibitor staurosporine decreased mRNA and protein expression of duodenal NaPi-IIb in broilers (9-13 d) (P < 0.05). Staurosporine increased the p-PKA/t-PKA protein expression ratio (P < 0.05), reduced the p-PI3K/t-PI3K and p-ERK/t-ERK ratios (P < 0.05), and had no effect on the p-p38MAPK/t-p38MAPK ratio (P > 0.05). Collectively, the PKA and PKC signaling pathways participate in VD₃-regulated intestinal P absorption in broiler chickens, and that the PKC pathway may function upstream of the PKA signaling pathway. This study lays a theoretical foundation for exploring the mineral homeostasis mechanisms by which VD₃ regulates intestinal P absorption in poultry.