Luminal lactate and tyrosine release during intestinal ischemia in rabbits

Introduction

The intestinal tract plays a central role in the protein catabolic response after injury and infection. Tyrosine (an index of overall proteolysis) and lactate release were evaluated in luminal gut perfusate during ligation of the superior mesenteric artery (SMA). The aim of this study is to determine whether tyrosine flow from the intracellular compartment to the lumen could occur during ischemia-induced gut injury.

Methods

Fourteen anesthetized New Zealand rabbits were allocated into two groups (group I: control, n = 5 and group II: ischemia, n = 9). SMA (QSMA) and aortic (Qaorta) flows were measured using ultrasonic flow probes. A segment from the ileum was isolated using two multilumen tubes with inflated balloons to delimit a closed segment to be perfused. In a second gut segment, a tonometric catheter (TRIP^® Tonometry Catheter; Datex, Finland) was placed. Animals in group II were submitted to ligation of SMA after baseline measurements. The concentrations of lactate and tyrosine were determined in serum and gut luminal perfusate (GLP). Tyronise was assayed by the fluorometric method as previously described [1].

Results

Lactate concentration significantly increased in GLP after ligation of SMA (from 0.15 ± 0.05 mEq/l to 3.5 ± 1.2 mEq/l at 2 hours) in comparison with the control (from 0.18 ± 0.43 mEq/l to 0.22 ± 0.12 mEq/l at 2 hours) (P < 0.05). Luminal tyrosine significantly increased during ischemia compared with the control at 2 hours (from 11.9 ± 8.9 mM/ml to 84 ± 22 mM/ml, group II; and from 6.9 ± 2.9 mM/ml to 15.3 ± 13.8 mM/ml, group I; P < 0.05).

Conclusion

Ischemia rapidly induces gut-derived proteolysis in rabbits.