CXCR4 protein concentrations are greater in the endometrium on Day 15 of pregnancy (P) compared to Day 15 of the estrous cycle (NP). Equal concentrations of endometrial protein from Day 15 pregnant and non-pregnant ewes were subjected to SDS-PAGE and Western blot analysis was performed to verify expression of CXCR4 (A). Data represent a minimum of 3 ewes per pregnancy status per day. The same protein samples were also immunodetected for actin to further verify equal loading of protein. Signals on Western blots were scanned on a STORM imager, converted to densitometric values, and analyzed. Values represent the mean ± SEM. Significant differences (P < 0.05) between endometrium from NP and P ewes are indicated by an asterisk (B).