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Title: EFFECTS OF EXOGENOUS SOMATOSTATIN AND CYSTEAMINE IN NET NUTRIENT FLUX ACROSS THE PORTAL-DRAINED VISERA AND LIVER OF SHEEP DURING INTRADUODENAL INFUSION OF STARCH HYDROLYSATE AND CASEIN

Author
item McLeod, Kyle
item BAUER, M. - UNIVERSITY OF KENTUCKY
item HARMON, D. - UNIVERSITY OF KENTUCKY
item REYNOLDS, C. - USDA ARS
item MITCHELL, JR, G. - UNIVERSITY OF KENTUCKY

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The manner and extent to which nutrients are absorbed and metabolized is controlled by small proteins called hormones. While a number of these regulatory proteins have been identified in, or associated with, tissues which comprise the gut (i.e. stomach, intestines, and liver), the complete functionality of each of these hormones is currently unknown. This experiment was conducted to investigate the role or function of one such hormone, called somatostatin, in sheep. The results of this study showed that when additional somatostatin was given to sheep, nutrient absorption and subsequent metabolism was decreased. Conversely, when natural levels of somatostatin were diminished, nutrient absorption and blood flow to the tissues of the gut were increased. It can be concluded from this experiment that somatostatin has a regulatory role in controlling nutrient absorption and metabolism in sheep. This information will aid scientists in mapping or identifying regulatory processes in the gut. To-this-end, a complete understanding of these regulatory processes will enable scientists to develop strategies that will maximize food and productive efficiency.

Technical Abstract: Eight polypay wethers (36 kg BW) fitted with hepatic portal, hepatic venous, mesenteric arterial and venous, and duodenal catheters were used 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 measured on d 14. Prior to flux measurements, wethers received an i.v. dose (0 h) of either 0 (vehicle) or 50mg x kg/BWx10/min 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 ug), continuous jugular infusion of SRIF-14 (5.0 ugxkg/(BWxh)) 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 PDV release of glucose, (x-amino N (AAN), ammonia N B-hydroxybutyrate (BHB), and oxygen consumption were decreased (P<=.10) and lactate release increased (P=.005) during SRIF infusion, while CSH increased (P<.05) PDV release of BHB and insulin and increased (P=.09) 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 oxygen consumption by the liver was decreased (P=.04) with exogenous SRIF and increased (P=.01) with CSH. Net total splanchnic AAN release and oxygen consumption were decreased (P<.10) with exogenous SRIF, while 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.