Detection of nitric oxide in exhaled air of different animal species usinga clinical chemiluminescence analyser

The aim of the present study was to evaluate the nitric oxide (NO) concentr ations present in end-expired gas (FENO) of different animal species under basal and stimulated conditions using a clinical chemiluminescence analyser , which has been developed for measurement of single exhalations in humans. Anaesthetised, tracheotomised and artificially ventilated guinea pigs, rat s and rabbits were prepared for recording systemic blood pressure and FENO. Stable levels of FENO were detected in expired air over a l-h observation period in the three animal species tested. Rabbits exhibited the highest co ncentrations and output (FENO 12.9 +/- 1.0 ppb, VNO 9.0 +/- 0.7 nl min(-1)) , followed by guinea pigs (FENO 6.2 +/- 0.70 ppb, VNO 1.7 +/- 0.19 nl min(- 1)) and rats (FENO 0.9 +/- 0.01 ppb, VNO 0.25 +/- 0.00 nl min(-1)). L-Argin ine (1 g kg(-1) i.v.) evoked significant increments in VNO in guinea pigs a nd rabbits but was ineffective in rats. However, L-arginine showed a direct effect on blood pressure in all the animal species tested, causing a rapid fall in the mean arterial blood pressure (MABP; 38, 48 and 50% decrease in rabbits, guinea pigs and rats, respectively; P < 0.05). An inhibitor of en dogenous NO synthesis, N-G-nitro-L-arginine methyl ester (L-NAME, 20 mg kg( -1) i.v.), decreased both basal and L-arginine-induced VNO in guinea pigs a nd rabbits, but was ineffective in rats. L-NAME increased MABP in all the a nimal species tested (58% in guinea pigs, 43% in rats and 18% in rabbits; P < 0.05). The results indicate that it is possible to detect NO in the exha led air of different animal species using a clinical chemiluminescence anal yser and that different species exhibit striking differences in the levels of basal and stimulated NO output. (C) 1999 The Italian Pharmacological Soc iety.