The mechanism of sevoflurane-induced cardioprotection is independent of the applied ischaemic stimulus in rat trabeculae  R.A. Bouwman, F.N.G. van't Hof, W. de Ruijter, B.J. van Beek-Harmsen, R.J.P. Musters, J.J. de Lange, C. Boer  British Journal of Anaesthesia  Volume 97, Issue 3, Pages 307-314 (September 2006) DOI: 10.1093/bja/ael174 Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 1 Simplified scheme of the mitochondrial ETC and the effects of cyanide and hypoxia on electron transport, ATP and ROS production. The ETC is located in the inner mitochondrial membrane and consists of different complexes, which contain the different elements of the chain. The ETC simultaneously transfers electrons and protons, resulting in oxidative phosphorylation and ATP synthesis at complex V. In complex IV, electrons are donated to O2, which react with 2H+ into H2O. Electron transport and oxidative phosphorylation are coupled, thus inhibition of electron transport leads to ATP depletion. Cyanide (CN−) combines with the oxidized haeme iron in cytochrome c oxidase, thereby preventing reduction of this oxidase. This results in the inhibition of the ETC and thus ATP depletion and Ca2+ overload. The O2 molecules react with free electrons derived from the ETC, resulting in the generation of ROS such as O 2 − (superoxide). During ischaemia, the availability of electron acceptor O2 is reduced. This prevents complex IV from donating electrons and therefore inhibits ATP production. Furthermore, the lower availability of O2 leads to more nitric oxide (NO), which also inhibits complex IV and reduces O2 consumption, resulting in the generation of superoxide and ONOO− (peroxynitrite). British Journal of Anaesthesia 2006 97, 307-314DOI: (10.1093/bja/ael174) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 2 Scheme for the 15 experimental groups of randomized isolated trabeculae. HYP=control hypoxia and recovery (sustained for 40 min after the time to rigor), MI=control metabolic inhibition (sustained for 30 min after the time to rigor), SEVO=sevoflurane, CHEL=chelerythrine, MPG=N-(2-mercaptopropionyl)-glycine, 5-HD=5-hydroxydecanoate, TIME=time control. British Journal of Anaesthesia 2006 97, 307-314DOI: (10.1093/bja/ael174) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 3 Developed force after recovery as a percentage of the initial developed force before the start of the experimental protocol (Fdev,rec) of HYP, HYP+SEVO, MI and MI+SEVO groups in combination with chelerythrine (CHEL; 6 µM), 5-hydroxydecanoate (5-HD; 100 µM) and n-(2-mercaptopropionyl)-glycine (MPG; 300 µM). The HYP protocol in addition to the MI protocol reduced the Fdev,rec, and preconditioning of the trabeculae before metabolic deprivation completely restored the Fdev,rec in both groups. The protective effect of sevoflurane was abolished in both HYP and MI groups by CHEL, 5-HD and MPG. HYP=hypoxia; MI=metabolic inhibition; Fdev=developed force; SEVO=sevoflurane; TIME=time control. * Indicates P<0.05 compared with TIME, † indicates P<0.05 compared with ISCHAEMIA, SEVO+CHEL, SEVO+5-HD and SEVO+MPG, ‡ indicates P<0.05 compared with HYP, # indicates P<0.05 compared with HYP+SEVO+MPG. British Journal of Anaesthesia 2006 97, 307-314DOI: (10.1093/bja/ael174) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 4 Time to peak, time to half relaxation, +dFdt and −dFdt expressed as a percentage of the initial values at the start of the experimental protocol in time controls and the HYP and HYP+SEVO groups. HYP tended to reduce the time to peak and time to half relaxation. Pretreatment with sevoflurane slightly prolonged the time to half relaxation. Interestingly, preconditioning with sevoflurane completely restored the decrease in positive dFdt as result of HYP. * Indicates P<0.05 compared with TIME CONTROL and HYP+SEVO, † indicates P<0.05 compared with TIME CONTROL, ‡ indicates P<0.05 compared with HYP+SEVO. British Journal of Anaesthesia 2006 97, 307-314DOI: (10.1093/bja/ael174) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions

Fig 5 Microscopic analysis of markers for necrosis and/or apoptosis in cross-sectional sections of isolated trabeculae. Haematoxylin–eosin staining in panels a through c showed in all sections an intact cellular morphology with no signs of disruption of the plasma membrane, cytosolic vacuolization or pyknosis of nuclei. In panels d through f, histochemical staining of the amount of myoglobin correlates with the shades of grey. No difference in myoglobin content was detected in trabeculae subjected either to MI or HYP compared with time controls. Representative images of the TUNEL analysis are shown in panels g through i. Blue fluorescence shows DAPI staining of the nuclei. Double-stranded DNA breakage in this TUNEL-analysis is detected by green fluorescence. Trabeculae subjected to MI or HYP showed no altered numbers of positive nuclei compared with time controls, as is shown by the absence of nuclei displaying both blue and green fluorescence. British Journal of Anaesthesia 2006 97, 307-314DOI: (10.1093/bja/ael174) Copyright © 2006 British Journal of Anaesthesia Terms and Conditions