Adiponectin, which is specifically and highly expressed in adipose tissue, has pleiotropic insulin sensitizing effects. Endothelin-1 (ET-1) is a potent vasoconstrictive peptide mainly produced by endothelial cells. We previously showed that ET-1 can induce insulin resistance in vitro and in vivo and proposed that it might regulate adiponectin expression and secretion, thus affecting the homeostasis of whole body energy metabolism. In the present study, we explored the regulatory effects of ET-1 on adiponectin expression and secretion and the underlying mechanisms in 3T3-L1 adipocytes using Northern blotting and ELISA. ET-1 was found to cause a significant time- and dose-dependent decrease in adiponectin expression, and this effect was inhibited by the ET_AR antagonist, BQ-610, but not by the ET_BR antagonist, BQ-788. To explore the underlying mechanism, we examined the involvement of the cAMP-dependent protein kinase A-, phospholipase A2-, protein kinase C-, and mitogen-activated protein kinase-mediated pathways using inhibitors and found that only PD98059 and U0126, inhibitors that blocked MEK's ability to activate the ERKs, prevented ET-1-induced downregulation of adiponectin. Furthermore, acute ET-1 treatment significantly stimulated adiponectin secretion by 3T3-L1 adipocytes and this effect was inhibited by the ET_AR antagonist, BQ-610, the IP₃ receptor blocker, 2-APB, and phospholipase C inhibitor, U73122, showing that the release of adiponectin stimulated by ET-1 was mediated through the ET_AR and the IP₃-pathway. In conclusion, ET-1 regulates adiponectin expression and secretion by two different signaling pathways in 3T3-L1 adipocytes. These finding suggested that the cardiovascular system affects adipocyte physiology by regulating the expression of adipocytokines and, consequently, energy homeostasis via vasoactive factors, such as ET-1.