EFFECTS OF EXOGENOUS SOMATOSTATIN AND CYSTEAMINE ON NET NUTRIENT FLUXACROSS 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 po rtal, hepatic venous, mesenteric arterial and venous, and duodenal cat heters in a crossover design experiment to determine the influence of somatostatin (SRIF)on splanchnic metabolism. Each crossover period con sisted of 14 d, with net flux of nutrients and hormones (venoarterial differences x 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 c ontinuous duodenal infusion (h 10 to 22) of a starch hydrolysate-casei n solution. Six sets of arterial, portal, and hepatic blood samples we re obtained (h 12 to 16), after which a prime. (10 mu g), continuous j ugular infusion of SRIF-14 (5.0 mu g.kg BW-1.h(-1)) was initiated and sampling protocol repeated(h 18 to 22). Cysteamine administration incr eased (P < .01, vs control) portal and hepatic blood flow in the absen ce of exogenous SRIF (CSH x SRIF, P < .01). Net portal-drained viscera (PDV) release of glucose, alpha-amino N, ammonia N, beta-hydroxybutyr ate, and oxygen consumption were decreased(P less than or equal to .10 ) and lactate release increased (P = .005) during SRIF infusion. The C SH increased (P < .05) PDV release of beta-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 CSR decreased (P = .09) net hepatic glucose output, whereas liver oxygen consumption was decreased (P = .04) with exogenous SRIF and inc reased (P = .01) with CSH. Net total splanchnic oc-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.