The Expression Of FGF23-Klotho And Its Renal Function Factors In Laying Hens At Different Laying Stages

Calcium and phosphorus are two kinds of important components of skeletal and egg shell,and are closely related to the shell quality in laying hens.With the prolongation of the laying period,the decline of egg shell quality has become one of the main problems that restrict the development of intensive poultry industry.Fibroblast growth factor 23(FGF23)that belongs to the family of fibroblast growth factor,mainly synthesized by osteocyte and osteoblast,was demonstrated recently as an important factor of calcium and phosphorus metabolism regulation in vivo.A number of results have suggested that FGF23 may be the coupling factor for regulating calcium and phosphorus metabolism between the intestinal-kidney-parathyroid-bones in mammals.It is generally accepted that FGF23 binds specifically to the Klotho-FGFRs(fibroblast growth factor receptor)complex in the kidney and activates the MAPK signaling pathway to regulate renal tubular calcium and phosphorus reabsorption in human and mammals.However,FGF23-Klotho in poultry body mechanism is not clear.In this paper,the expression of FGF23 and Klotho mRNA skeletal muscle,kidney,heart,liver,osteoarticular.bone,parathyroid,adrenal,shell-gland,ovary,hypothalamus,pituitary and duodenum were detected in laying hens.The expression levels of bony FGF23 mRNA and renal FGF23-Klotho acting factors mRNA was measured by real-time quantitative RT-PCR in different laying period hens.At the same time,the egg shell quality was investigate using conventional methods.The objective of the study was to investigate the changes of FGF23-Klotho action factors in the kidney of laying hens at different stages,so as to provide a basis for further research on the roles of FGF23 and Klotho in laying hens.The results showed that:1.FGF23 mRNA were expressed in the osteoarticular,ovary and liver of laying hens.Klotho mRNA were expressed in the pituitary,heart,duodenum,ovary,shell gland,kidney,adrenal,parathyroid and hypothalamus of the laying hens.2.The expression level of osteoarticular FGF23 mRNA in laying early and peak period was significantly higher than that of laying late stage.The expression levels of renal FGFR1,FGFR3,FGFR4,CaBP-D28k and PMCAlb mRNA in laying peak period were significantly higher than those in laying early period.The expression levels of TRPV5 and Cyp24a1 mRNA were significantly lower than those in early laying period.3.The eggshell thickness,egg shell strength and egg shell ratio of late laying stage hens were significantly lower than those of early and peak laying stage.The present results indicated that the decline of eggshell quality in late laying period was closely related to the decrease of renal calcium reabsorption capacity.