Effects of Exogenous Somatostatin and Cysteamine on Net Nutrient Flux Across the Portal-Drained Viscera and Liver of Sheep during Intraduodenal Infusion of Starch Hydrolysate and Casein

We used eight Polypay wethers (36 ± .6 kg BW) fitted with hepatic portal, hepatic venous, mesenteric arterial and venous, and duodenal catheters in a crossover design experiment to determine the influence of somatostatin (SRIF) on splanchnic metabolism. Each crossover period consisted of 14 d, with net flux of nutrients and hormones (venoarterial differences × blood flow) measured on d 14. Before flux measurements, wethers received an i.v. dose (0 h) of either 0 (vehicle) or 50 mg·kg BW^-1·10 min^-1 cysteamine (CSH, SRIF-depleting agent) followed by a continuous duodenal infusion (h 10 to 22) of a starch hydrolysate-casein solution. Six sets of arterial, portal, and hepatic blood samples were obtained (h 12 to 16), after which a primed (10 μg), continuous jugular infusion of SRIF-14 (5.0 μg·kg BW^-1·h^-1) was initiated and sampling protocol repeated (h 18 to 22). Cysteamine administration increased (P < .01, vs control) portal and hepatic blood flow in the absence of exogenous SRIF (CSH × SRIF, P < .01). Net portal-drained viscera (PDV) release of glucose, α-amino N, ammonia N, β-hydroxybutyrate, and oxygen consumption were decreased (P ≤ .10) and lactate release increased (P = .005) during SRIF infusion. The CSH increased (P < .05) PDV release of β-hydroxybutyrate and insulin and increased (P = .09, CSH alone vs control) net release of glucose in the absence of exogenous SRIF. Exogenous SRIF increased (P = .10) and CSH decreased (P = .09) net hepatic glucose output, whereas liver oxygen consumption was decreased (P = .04) with exogenous SRIF and increased (P = .01) with CSH. Net total splanchnic α-amino N release and oxygen consumption were decreased (P < .10) with exogenous SRIF, but CSH increased (P < .05) insulin release and oxygen consumption. These data provide initial evidence for a regulatory involvement of SRIF in visceral metabolism in ruminants.