Jejunal mucosal protein synthesis: validation of luminal flooding dose method and effect of luminal osmolarity

To validate a system to study acute regulation of protein synthesis in inte stinal mucosa by luminal nutrients, we compared the fractional rate of prot ein synthesis (K-s) in jejunal mucosa using the intravenous flooding dose t echnique with the administration of a comparable concentration and specific activity of tracer in a luminal perfusate. Routes of tracer administration and surgery and perfusion trauma had no effect on mucosal K-s. Furthermore , four 10-cm jejunal segments (within a piglet) simultaneously but separate ly perfused with a luminal flooding dose had similar K-s values (mean, 43 /- 2%/day; P > 0.05). Nutrient solutions perfused through four intestinal s egments within an animal did not affect plasma levels of most amino acids o r glucose. Because cellular hydration is important in regulating metabolism , the effects of physiological variation in luminal osmolarity were studied . Luminal osmolarities between 250 and 380 mosM did not affect mucosal K-s. The system described allows multiple comparisons within an animal and prov ides a robust model to study acute modulation of protein synthesis in intes tinal mucosa by luminal stimuli.