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

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1.7.1 Adenosine Receptor Stimulation It has been shown that stimulation of the adenosine A, receptor mimics ischaemic preconditioning protection [ 192]. Also blockade of the receptors during a typical ischaernic preconditioning protocol abolishes card ioprotect ion in the rabbit heart [192] and in other species [ 15,521. These data and others established the involvement of the adenosine receptor as a mediator of ischaernic preconditioning protection. There is also evidence that preconditioning involves a subtype of adenosine receptor, the A., receptor 19 11. Adenosine is released from Ischaernic myocytes (due to high energy phosphate breakdown), and is thought to act as a local regulator for the modulation of cellular function. Adenosine may also be released from the endothelium during ischaernia [29]. It appears to act on adenosme receptors, subsequently causing protection by modulation of a Gj protein. Also, during ischaemia, numerous other metabolites are released locally by the myocardium. These include catecholamines and bradykinin that have been proposed as triggers of ischemic preconditioning [1041. The role of adenosine in ischaemic preconditioning has been extensively examined in various animal models [15,52,192,281]. Adenosine A, receptors couple to PKC [ 1381 With activation of PKC, appearing to be necessary for preconditioning protection to occur in the rabbit [3491, the rat [281], and possibly the human myocardium [282]. Activation of PKC causes phosphorylation of a secondary effector protein, possibly the MAPK system [46], which may bring about protection by triggering a sequence of biochemical reactions in the cytosol. Gi proteins are also involved in the signal transduction pathway of ischernic preconditioning [306], 17
and these proteins have been suggested, in rat ventricular myocytes, to link adenosine receptors to an end-effector, initially thought to be the Kxj 1, channel [ 169]. The coupling to the Gi protein may explain why activation by other trigger receptors coupled to G proteins can also mimic preconditioning. Liu et al [191] have suggested that it may be necessary for multiple receptors to be populated in order to trigger preconditioning protection, and that although ischaernia may result in many receptors being occupied, the actual importance of individual receptors may vary amongst species. It may be necessary to exceed a certain threshold of receptor occupancy in order to stimulate the rest of the pathway leading to protection [ 1911. 1.7.2 ATP-sensitive potassium (KATP) channel It has been suggested that the ATP-sensitive potassium (K.. %-I-p) channel may be the final end-effector of the mechanism of ischaemic preconditioning protection, since opening of these channels may cause an efflux of potassium which would shorten the cardiac action potential and so limit ATP depletion and calcium accumulation [14]. Experimental evidence for involvement of the KATP channel in preconditioning exists for the pig [2731, and the dog [14,107], but studies In the rat [113,193] and the rabbit [305,3091 have been conflicting. Ischaernic preconditioning may therefore release adenosine which may activate PKC leading to protein phosphorylation ultimately altering the KATP channel sensitivity to ATP, leading to an earlier or greater channel opening during sustained ischaernia. As much of the thesis involves investigation into the role played by the ATP-sensitive K' channel (K,, %. I-p channel) in protection of human atrium, the biology, the pharmacology 18
Page 1 and 2: ISCHAEMIC PRECONDITIONING OF THE HU
Page 3 and 4: ABSTRACT Ischaemic preconditioning
Page 5 and 6: andomised clinical study with the f
Page 7 and 8: CHAPTERI Introduction 35 Matefials
Page 9 and 10: Discussion 151 CHAPTER Vill Conclus
Page 11 and 12: 44 CK leakage and MTT reduction on
Page 13 and 14: The Wellcome Trust and The British
Page 15 and 16: Presentations International "The Ef
Page 17 and 18: Abbreviations An attempt has been m
Page 19 and 20: 1.1 Introduction Ischaernic heart d
Page 21 and 22: 1.2 Myocardial Ischaemia Myocardial
Page 23 and 24: hours up to several days to complet
Page 25 and 26: phosphates and its influence on hyd
Page 27 and 28: 1.4 Myocardial Protection This refe
Page 29 and 30: performed. This process is repeated
Page 31 and 32: 1.6 Possible Mechanisms of Ischaemi
Page 33: kilodalton stress proteins. These p
Page 37 and 38: K vi-1, channels were initially fou
Page 39 and 40: tissues the K.. %,.,, channels are
Page 41 and 42: Subsequently, Jaburek et al 1145] i
Page 43 and 44: venous capacitance vessels. At ther
Page 45 and 46: 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
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3.2 MATERIALS AND METHODS-. 3.2.1 E
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A117'reduction- At the end of the e
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-4 ýi r. () .1 a 0 1 tli n F5* - C
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v M. %; n C) .0 ý U ý ý - - - -2
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leakage resulting from precondition
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3.5 DISCUSSION: The present studies
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during cardiac surgery totalling 10
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different. The cellular mechanisms
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cn Je 8 7 6 5 4 1 0 0.8 0.7 0.6 0.5
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8 6 C) 2 0.7 0.6 Q) 0.5 0) E 25 0.4
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6 5 CY) ,u3 CF) m -ýe m 2 1 0 -0.8
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CHAPTERIV THE ROLE OF THE KATPCHANN
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It has been reported that K.. %-I-p
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0 a- I a 3 I cr =r Cl. 2 qQ 0'-ý 0
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Figure 4.7 shows that ischaemia alo
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Figure 4.2 Dosc-responsc experiment
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Figure 4.4 Dose-response experiment
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Figure 4.6 Dosc-response experiment
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1 0.9 -ý 0.8 0.7 E 0.6 0.5 0.4 0.2
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activity, and showed that diazoxide
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Furthermore, Van den Hoek et al [3
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mechanism by which the opening of m
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5.1 INTRODUCTION: Within the enormo
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5.2 MATERIALS AND METHODS: 5.2.1 Ex
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M77'rechiction: At the end of the e
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oc 0 0 cr F; * 10 eb I ý; o I 5 0
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Pages missing original in the
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esulted in a decrease of CK leakage
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are on long-term hypoglycaernics or
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absence of uniformity of expeniment
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5.7 Conclusion Preconditioning is a
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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,
Page 215 and 216:
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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