Effects of knockout of AT1A receptor gene (AT1A-KO) on the cold-induced increase in cardiac endothelin-1 production. The measurement was done in mice expose to cold (5°C) for 5 weeks. AT1A-KO-Cold, AT1A-KO mice exposed to cold (5±2°C); AT1A-KO-Warm, AT1A-KO mice maintained at room temperatures (warm, 25±2°C); WT-Cold, wild type mice maintained at cold; WT-Warm, wild type mice maintained at room temperatures (warm). ***p<0.001 vs the WT-Warm group. N=6.