The purpose of this study was to evaluate whether circulating ghrelin and growth hormone (GH) concentrations in cattle are regulated by endothelin-1 (ET-1), endothelin-3 (ET-3), and secretin. Six Holstein steers (242+/-1 d old, 280.5+/-4.4 kg body weight [BW]; mean+/-SEM) were allocated randomly in an incomplete Latin square design to receive each of 4 treatment compounds (vehicle, ET-1, ET-3, and secretin) with 1-d intervals between successive treatments. The treatment compounds were injected intravenously via a catheter inserted into the external jugular vein of each steer. Blood was sampled from the indwelling catheter at -30, -15, 0, 5, 10, 15, 20, 30, 45, 60, 90, 120, 150, and 180 min. Plasma ghrelin and GH responses to the treatment compounds were measured by a double-antibody radioimmunoassay system. Data were analyzed by using a MIXED procedure of SAS, version 9.1. Plasma acyl ghrelin, total ghrelin, and GH concentrations were increased by both ET-1 and ET-3 injection (ET-1 injection: 311+/-15 pg/mL vs 245+/-15 pg/mL, 2.4+/-0.2 ng/mL vs 1.61+/-0.05 ng/mL, 4.73+/-0.92 ng/mL vs 1.17+/-0.09 ng/mL for acyl ghrelin, total ghrelin, and GH, respectively; ET-3 injection: 337+/-27 pg/mL vs 245+/-15 pg/mL, 2.6+/-0.1 ng/mL vs 1.61+/-0.05 ng/mL, 5.56+/-0.97 ng/mL vs 1.17+/-0.09 ng/mL for acyl ghrelin, total ghrelin, and GH, respectively; P<0.01). Ghrelin and GH concentrations were not changed by secretin injection throughout the experimental periods. These results indicate that ET-1 and ET-3 stimulate ghrelin and GH secretion in cattle and demonstrate for the first time that endogenous ghrelin released in response to endothelin injection stimulates GH secretion in vivo in cattle.