NG-NITRO-L-ARGININE METHYL ESTER(L-NAME) REDUCE DIAPHRAGM ENDURANCE TIME IN RAT

Abstract

S152 INTRODUCTION: We have previously demonstrated that Human recombinant interleukin 1 beta (HrIL-1 beta) decreases diaphragm endurance time in vitro. L-NAME, nitric oxide synthase inhibitor, was administrated to the experimental bath, to prevent diaphragm function before adding HrIL-1. But there were no improvements in endurance time. The aim of this study was to investigate the effect of L-NAME in normal rat diaphragm. METHODS: Male Sprague-Dawley rats(150[similar]175g) were anesthetized with sodium pentobarbital. Two, 10mm wide muscle strips without phrenic nerve were dissected from medial aspect of each diaphragm. The strips were mounted in a water jacketed tissue bath containing Krebs solution and 0.1% bovine serum albumin(BSA). The central tendon was attached to an isometric force transducer. Baths were maintained at 37[degree sign]C. The pH of the bath were maintained approximately 7.4 during the experiment. 95% O2 and 5% CO2 were bubbled into the bath and D-tubocurarine was added. Supramax, stimulation voltage and optimal muscle length were determined for each strip. L-NAME(final bath concentrations of 300,30 and 3 [micro sign] M) or D-NAME(300 [micro sign] M) was added with 0.1% BSA into the bath. An equal volume of 0.1% BSA was added to control baths. After 1 hour, single twitch force(2 ms duration) and tetanic forces(400 ms trains of 2 ms impulses at 10,20, 60,100 Hz) were measured. Syrips were fatigued (20Hz, 0.33s trains, 1 train/sec.) until 50% of initial maximal tension was achieved. Single twitch and force frequency relationships were measured immediately, 10,30 and 60 min. after fatigue. Force measurements were normalized for cross sectional area. Endurance time was defined as the time in seconds required to achieved 50% initial maximal tension. Post-fatigue forse divided by baseline force defined fatigue resistance (FRI). The data was analyzed using unpaired t-test and ANOVA analysis. RESULTS: (Table 1)Table 1At 300 [micro sign]M L-NAME there was a statistical significant difference in endurance time. At 30 and 3 [micro sign] M L-NAME there were no differences. Comparing D-NAME vs. 300 [micro sign] M L-NAME, there was a significant difference in endurance time. However, there was no difference between control and D-NAME. There were no significant difference in FRI, 1/2 relaxation time and contraction time. CONCLUSIONS: L-NAME at higher concentrations in this model is associated with a decrease endurance time. Whereas D-NAME did not impair diaphragm function. This data suggests that NO may play a role in the respiratory muscle function.