ischaemic preconditioning of the human heart. - Leicester Research ...

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preconditioning may be identical in all species. Certainly, the stimulation of membrane receptors such as A, /A. 3 and (xl-adrenoreceptors and the activation of protein kinase C and K vri, channels have been shown to be involved in the majority of the animal species studied [ 15,187,273,275 land in man [52,601 My finding that preconditioning is a graded phenomenon is also compatible with the notion that a number of triggers could be activated to achieve protection The realization that preconditioning is a phenomenon probably shared by all mammalian species studied including man and the evidence that it maybe elicited through identical molecular pathways, it makes possible that the results obtained from laboratory based studies may be extrapolated to the clinical setting with a high degree of confidence. Second Window of Protection My studies are again the first to demonstrate the existence of a second window of protection in the human myocardium. However, I have shown that the second window is not as protective as the first window, a result that is consistent with other reports in anaesthetized rabbits and dogs [177,201,3351. The issue is not without controversy and some investigators [249,298] have reported that in anaesthetized rabbits preconditioning does not result in infarct size reduction if the ischaemic insult is applied in the following 24 or 48 hr. The reasons for these discrepancies are not entirely clear, but differences in the experimental preparations and protocols should be taken into account. Preliminary studies conducted in the laboratory showed that the extent of protection obtained in the second window of preconditioning was similar with one cycle and with repeated cycles of ischaernia as long as the total ischaemic stimulus was between 4 and 5 min (data not shown). The contrast between the universal presence of the first window of protection and the controversial second window may suggest that the mechanism underlying the two %"ndows are 81
different. The cellular mechanisms underlying the second window are not fully understood at present. Some experimental evidence for the involvement of adenosine receptor stimulation and activation of protein kinase C (PKC) in the development of delayed protection has been reported in rabbits [24-251. However, PKC could influence a host of other signal transduction pathways and it is possible that other protein kinase events play a role in the mechanism. Certainly, other end-effectors have been implicated in the second window. These include the intracellular antioxidant superoxide dismutase (SOD) [3361, heat shock proteins [3471 and nitric oxide synthetase [2381. At present, there is limited evidence to suggest that channels are involved in the delayed phase of protection [941. it is quite clear that further research is needed in this area Limitations of the Study and Clinical Implications The present work has several limitations. First, in our preparation ischaernia was induced by removingO2 and nutrient substrate but toxic metabolites, usually accumulated during ischaemia, freely diffused into the incubation media ("simulated ischaemia") I accept that there are important differences between this model and true ischaernia, particularly in respect to the washout of ischaemic metabolites and pH changes. Second, I used atrial tissue and any extrapolation to ventficular myocardium must be conducted with caution, however, Yellon's group [3251 has suggested that identical protection can be obtained by preconditioning in both tissues. Third, right atria] specimens were obtained from patients subjected to medical treatments (e. g. nitrates, O-blockers, calcium antagonists) that potentially may themselves influence i schaem ia/reoxygenat ion injury and the protection induced by preconditioning. Fourth, this model is an in-vilro preparation and the results may not completely apply to the clinical setting, although the findings during coronary artery occlusion in the course of PTCA may suggest that protection by preconditioning can be achieved with similar protocols in both situations. 82
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ISCHAEMIC PRECONDITIONING OF THE HU
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ABSTRACT Ischaemic preconditioning
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andomised clinical study with the f
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CHAPTERI Introduction 35 Matefials
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Discussion 151 CHAPTER Vill Conclus
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44 CK leakage and MTT reduction on
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The Wellcome Trust and The British
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Presentations International "The Ef
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Abbreviations An attempt has been m
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1.1 Introduction Ischaernic heart d
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1.2 Myocardial Ischaemia Myocardial
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hours up to several days to complet
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phosphates and its influence on hyd
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1.4 Myocardial Protection This refe
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performed. This process is repeated
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1.6 Possible Mechanisms of Ischaemi
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kilodalton stress proteins. These p
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and these proteins have been sugges
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K vi-1, channels were initially fou
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tissues the K.. %,.,, channels are
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Subsequently, Jaburek et al 1145] i
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venous capacitance vessels. At ther
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preconditioning to be investigated
Page 47 and 48: In the angioplasty model, Tomai et
Page 49 and 50: patients were randomized into two g
Page 51 and 52: CHAPTER 11 THE HUMAN RIGHT ATRIAL T
Page 53 and 54: inexpensive. Briefly in this model,
Page 55 and 56: of each ischemic period, slices wer
Page 57 and 58: 30 nini FO linlin L 60 min 120 inin
Page 59 and 60: In Study 3 (see Figure 2.4), slices
Page 61 and 62: D. Metabolite analysis Samples were
Page 63 and 64: leakage is calculated as the net LD
Page 65 and 66: B. Effect of the severity of ischae
Page 67 and 68: 2.11 DISCUSSION: The present studie
Page 69 and 70: clearly insufficient to induce myoc
Page 71 and 72: The present model may facilitate th
Page 73 and 74: 2.12 Conclusiow I have characterise
Page 75 and 76: 3.5 3 V 2.5 3: m Je m Z0 z 2 1.5 0.
Page 77 and 78: (3 3 2.5 a 1.5 - -r T 0 2 0.5 0 I P
Page 79 and 80: Q oro . 21 . 0 'a IP 10 '. R -C3 A
Page 81 and 82: =3 0 h X CD 0 x CD :3 0 , 7, CD 0 0
Page 83 and 84: CHAPTER III PRECONDITIONING THE HUM
Page 85 and 86: 3.2 MATERIALS AND METHODS-. 3.2.1 E
Page 87 and 88: A117'reduction- At the end of the e
Page 89 and 90: -4 ýi r. () .1 a 0 1 tli n F5* - C
Page 91 and 92: v M. %; n C) .0 ý U ý ý - - - -2
Page 93 and 94: leakage resulting from precondition
Page 95 and 96: 3.5 DISCUSSION: The present studies
Page 97: during cardiac surgery totalling 10
Page 101 and 102: cn Je 8 7 6 5 4 1 0 0.8 0.7 0.6 0.5
Page 103 and 104: 8 6 C) 2 0.7 0.6 Q) 0.5 0) E 25 0.4
Page 105 and 106: 6 5 CY) ,u3 CF) m -ýe m 2 1 0 -0.8
Page 107 and 108: CHAPTERIV THE ROLE OF THE KATPCHANN
Page 109 and 110: It has been reported that K.. %-I-p
Page 111 and 112: 0 a- I a 3 I cr =r Cl. 2 qQ 0'-ý 0
Page 113 and 114: Figure 4.7 shows that ischaemia alo
Page 115 and 116: Figure 4.2 Dosc-responsc experiment
Page 117 and 118: Figure 4.4 Dose-response experiment
Page 119 and 120: Figure 4.6 Dosc-response experiment
Page 121 and 122: 1 0.9 -ý 0.8 0.7 E 0.6 0.5 0.4 0.2
Page 123 and 124: activity, and showed that diazoxide
Page 125 and 126: Furthermore, Van den Hoek et al [3
Page 127 and 128: mechanism by which the opening of m
Page 129 and 130: 5.1 INTRODUCTION: Within the enormo
Page 131 and 132: 5.2 MATERIALS AND METHODS: 5.2.1 Ex
Page 133 and 134: M77'rechiction: At the end of the e
Page 135 and 136: oc 0 0 cr F; * 10 eb I ý; o I 5 0
Page 137 and 138: Pages missing original in the
Page 139 and 140: esulted in a decrease of CK leakage
Page 141 and 142: are on long-term hypoglycaernics or
Page 143 and 144: absence of uniformity of expeniment
Page 145 and 146: 5.7 Conclusion Preconditioning is a
Page 147 and 148: 0.9 0.8 07 m 0.6 E -0 0t 4 0.3 02 0
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-0 1.2 1 &8 0.6 04 0.2 o Aerobic Is
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6.1 INTRODUCIFION' Life expectancv
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(MI-T) to blue t'()rmazan product C
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The demonstration that ischaemic in
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Table 61 Patients' demographic and
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Nure 6,1: Creatine Kinase (CK) leak
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CHAPTER VII IN VIVO STUDIES ON T"E
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The apparent discrepancy bet,.,,, e
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In the off-pump group, coronary byp
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eduction as described in section 3.
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7.4.2 In vitro studies Figures 7.3A
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preconditioning stimulus in man is
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myocardium. Several investigators [
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Table 7.2 - Patients haemod-v-namic
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(0 -I 3 CD CD CD 1 3 0 :3 0 0 =r w
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0 co t X 3 co 0 0 Cumulative Releas
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-& a) c) UT 0 =r w CD 3 CD 0 1ý (a
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When ischaernic preconditioning was
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evidence tbr the involvement ot'PKC
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institution o fcardiopu Imo nary by
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Biblioqraphv 1. Abete P, Ferrara N,
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14. Auchampach J, Cavero, I and Gro
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27. Becker LB, Van den Hoek TLV, Sh
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41. Bums PG, Krunkenkamp IB, Calder
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55. Cohen G, Shirai T, Weisel RD, e
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69. Currie RW and White FP (1983).
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83. Downey JM, Liu GS and Thornton
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97. Ganote C, Armstrong S and Downe
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110. Grover GJ, D'Alonzo A, Hess T,
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122. Hamilton T and Weston A (1989)
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137. Hu H, Sato T, Seharaseyon J, L
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151. Jennings R, Steenbergen C, Kin
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164. Kelpzig H, Kobert G, Mafter C,
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178. Lamping K, Christensen C, Pelc
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192. Liu GS, Thornton J, Van Winkle
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206. Maulik N, Yoshida T, Das DK. (
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219. Miyawaki H, Zhou X, Ashraf, M.
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233. Okazaki Y, Kodama K, Sato H, K
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248. Pryzlenk K, Li G, Whittaker P
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260. Saito S, Tamura Y, Moriuchi M,
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274. Schulz R, Post H, Valhaus C, e
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288. Stewart JR, Blackwell WH, Crut
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300. Tani M, Suganuma Y, Hasegawa H
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312. Tosaki A, Engelman DT, Engelma
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324. Walker D, Marber M, Walker J a
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337. Yamashita N, Nishida M, Hoshid
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351. Zhang JG, Lindup WE. (1993). R
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444 J. -G. Zhang and others are dif
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446 J. -G. Zhang and others Assessm
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448 J. -G. Zhang and others 0.9 0.8
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450 J. -G. Zhang and others C E 07
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4S2 J. -G. Zhang and othen effects
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ELSEVIER Abstract Cardiovascular Re
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936 S. Ghosh et al. / Cardiovascula
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938 S. Ghosh et al. / Cardiovascula
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940 S. Ghosh et al. [41 Goto M, Liu
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712 0" et &L h wcomMe geg in Obwa»
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714 Gbosb ot aL hmoo dmoWmbDbsnedH
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716 chmä et aL Pi unamOso äu In O
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718 ehe* et &L ditioning in the hum
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