|Yen, Jong Tseng|
Submitted to: Proceedings of the International Symposium on Digestive Physiology in Pigs
Publication Type: Proceedings
Publication Acceptance Date: 3/14/2003
Publication Date: 5/14/2003
Citation: BREGENDAHL, K., LIU, L., FAN, M.Z., CANT, J.P., BAYLEY, H.S., MCBRIDE, B.W., MILLIGAN, L.P., YEN, J. MEASUREMENT OF THE FRACTIONAL PROTEIN SYNTHESIS RATES IN VISCERAL ORGANS OF WEANLING PIGS BY INTRAPERITONEAL INJECTION OF A FLOODING DOSE OF L-[RING-2H5]PHENYLALANINE. PROCEEDINGS OF THE INTERNATIONAL SYMPOSIUM ON DIGESTIVE PHYSIOLOGY IN PIGS, BANFF, ALBERTA, CANADA. VOLUME 2, PAGES 43-45. 2003.
Technical Abstract: In weanling pigs, use of the flooding-dose technique to measure fractional protein synthesis rate (FSR) requires surgical placement of catheters for intravenous injection (IV) of the tracer. The surgery and catheters carry with them risks of infection, which are of special concern if the pigs are housed in an unsanitary environment for investigations of metabolic effects of various dietary strategies. We hypothesized that an intraperitoneally (IP) injected flooding dose could be used to measure FSR of weanling pigs, negating the need for surgery and easing tracer administration. Five blocks of five littermate gilts were weaned at 16 d of age and fed a pelleted starter diet. On d 8 post-weaning, 1.5 mmol/kg BW of L phenylalanine (Phe), 40% enriched with L-[ring-2H5]-Phe, in saline (154 mM) was injected IP according to a randomized complete block design with euthanasia and tissue collection at 15, 30, 45, 60, or 75 min post-injection. Blood samples were collected immediately before Phe injection and euthanasia. Visceral organs were rinsed thoroughly in ice-cold saline, subsampled, immediately frozen in liquid nitrogen, and stored at -70°C until analysis. Enrichment of Phe in the free and bound pools was measured by gas chromatography-mass spectrometry. Enrichment of isotopic Phe in plasma increased logarithmically (P<0.05) from 0 to 33% and reached 99% of maximal enrichment 15 min post-injection. The free-pool enrichment of individual visceral organs reached levels similar to that of plasma 15 min after injection and did not change thereafter (P>0.05). The bound pool enrichment in all organs increased linearly over time (P<0.05). The FSR of individual visceral organs, calculated at each of the five time points, did not differ (P>0.05) and the overall FSR (%/d; mean ± SE, n = 5) was therefore calculated for liver (44±3), kidney (33±1), stomach (42±2), spleen (32±1), pancreas (96±6), proximal (74±3) and distal (69±4) small intestine, cecum (48±2), and colon (42±2). In conclusion, the free pools in plasma and visceral organs were evenly enriched (33%) 15 min after an IP injection of a flooding dose of tracer L-Phe and the calculated FSR of individual visceral organs did not differ over time. Thus, IP tracer injection is effective as IV injection in measuring the FSR of visceral organs, which can be initiated as early as 15 min post-injection in young pigs.