Time course of CD14, CXCL1, and SAA3 gene expression during LPS-induced mastitis. Mice were killed at 1, 2, and 6 h after intramammary infusion of either saline (−) or LPS (+). Total RNA (20 μg) was isolated from mammary glands and subjected to Northern blot analysis for expression of CD14, CXCL1, and SAA3. The GAPDH band serves as a control for RNA integrity and loading amount.