Abstract
This study investigated the molecular regulation of uterine calcium ion (Ca²⁺) transport during the oviposition cycle in Guizhou Sansui ducks. Uterine tissues were collected at 0, 2, 5, and 16 h after oviposition to determine Ca²⁺ concentrations and quantify the mRNA levels of ten Ca²⁺ transport-related genes, including transient receptor potential vanilloid 6 (TRPV6), inositol 1,4,5-trisphosphate receptor type 1 (IP3R1), inositol 1,4,5-trisphosphate receptor type 2 (IP3R2), inositol 1,4,5-trisphosphate receptor type 3 (IP3R3), solute carrier family 4 member 4 (SLC4A4), solute carrier family 4 member 9 (SLC4A9), potassium inwardly-rectifying channel subfamily J member 15 (KCNJ15), sodium channel epithelial subunit gamma (SCNN1G), adenosyl homocysteinase-like 1 (AHCYL1), and protein kinase C alpha (PRKCA). In addition, the expression profiles of these ten genes were assessed across 12 tissues (heart, liver, spleen, lung, kidney, large intestine, small intestine, duodenum, pancreas, proventriculus, gizzard, and pectoral muscle) at the four oviposition time points. The results showed that the Ca²⁺ concentration in the uterine tissue was relatively low at 0 h, increased at 2 h and 5 h (P < 0.01), and reached its peak at 16 h (P < 0.01). The expression of the ten genes showed an overall upward trend, with TRPV6 slightly decreasing initially and then continuously increasing. Correlation analysis revealed that at 0 h, uterine Ca²⁺ concentration was negatively correlated with IP3R2 and KCNJ15 (P < 0.05), while IP3R2 was positively correlated with KCNJ15 (P < 0.05). At 2 h, TRPV6 expression was negatively correlated with both Ca²⁺ concentration and KCNJ15 (P < 0.05). At 16 h, Ca²⁺ concentration was negatively correlated with SCNN1G but positively correlated with SLC4A9 (P < 0.05). All ten genes were expressed across 12 tissues, showing distinct temporal and spatial patterns. These results suggest that TRPV6, IP3Rs (IP3R1, IP3R2, and IP3R3), SLC4A4/9, KCNJ15, SCNN1G, AHCYL1, and PRKCA may cooperatively regulate uterine Ca²⁺ absorption, intracellular release, and local homeostasis, while their tissue-specific expression reflects systemic regulation of calcium metabolism.