Genetic Background and Dietary Phosphorus Influence Pituitary Gene Expression in Pigs

The impact of dietary phosphorus (P) on some pituitary hormones has been well‐established; however the affect of genetics on this impact has not been investigated. Gilts (n=48, 3 wk old) sired by 2 different lines (PIC337 and PIC280), were fed either a P adequate (P+) or a 20% P deficient (P‐) diet for 14wk. At the end of the trial, whole pituitaries were collected for analysis of gene expression by real‐time PCR. PIC337 sired pigs tended to have higher expression of calcitonin receptor (CTR, 1.95 fold, p ≤ 0.11) and vitamin D receptor (VDR, 2.1 fold, p ≤ 0.08) than their PIC280 sired counterparts. Pigs fed P+ also tended to have higher expression of CTR (1.81 fold p ≤ 0.15) and parathyroid hormone receptor (PTHR, 1.6 fold, p ≤ 0.17) than P‐ fed pigs. Among PIC280 sired pigs, the P+ pigs had 4 fold higher expression (p ≤ 0.06) of growth hormone (GH) receptor than the P‐ pigs. The levels of GH receptor mRNA in the PIC280 P+ were not different from any of the PIC337 pigs. Levels of GH mRNA tended to be 2.35 fold higher (p ≤ 0.15) in PIC337 P+ pigs compared to their P‐ littermates. PIC337 P+ pigs also tended (p ≤ 0.11) to have 2.78 fold higher levels of GH mRNA than the PIC280 P+ pigs. Alterations in gene expression in the pituitary may help explain differences seen between these genetic backgrounds in P homeorhesis. Understanding the impact of genetic background on pituitary function may provide insight into its role in affecting P homeostasis and bone integrity.