Sulfated cholecystokinin‐8 increases ghrelin secretion but does not affect oxyntomodulin in Holstein steers

The effect of appetite regulatory hormone cholecystokinin (CCK) on the secretions of oxyntomodulin (OXM) and ghrelin, and the effect of ghrelin on the secretions of CCK and OXM were studied in ruminants. Eight Holstein steers, 7 months old, 243 ± 7 kg body weight (BW), were arranged in an incomplete Latin square design (8 animals × 4 treatments × 4 days of sampling). Steers were intravenously injected with 10 µg of sulfated CCK‐8/kg BW, 20 µg of acyl ghrelin/kg BW, 100 µg of des‐acyl ghrelin/kg BW or vehicle. Blood samples were collected from ?60 min to 120 min relative to time of injection. Plasma concentrations of ghrelin, sulfated CCK and OXM were measured by double‐antibody radioimmunoassay. Plasma acyl ghrelin was increased to peak level (428.3 ± 6 pg/mL) at 60 min after injection of CCK compared with pre‐injected levels (203.3 ± 1 pg/mL). These results showed for the first time, that intravenous bolus injection of CCK increased ghrelin secretion in ruminants. In contrast, injection of ghrelin did not change CCK secretion. Administration of ghrelin or CCK has no effect on plasma OXM concentrations. In conclusion, our results show that administration of CCK increased ghrelin secretion but did not affect OXM release in ruminants. Ghrelin did not affect the secretions of CCK and OXM.