Indian J Ph sial Pharmacol 1995; 39(3): 283-286

THE ISOLATED AIR PERFUSED RAT HEART

B. V. VENKATARAr·,iIANt, S. DUTT'\ J. CZEKAJEWSKF* L. ENNERFELT':"" AND C. WILLIAMS':"~ Department o{ Pharmacology, St. John's Medical College, Banaalore - 560 034.

( Received on May 30, 1994 )

Abstract: A simple method ha been developed for continuous monitoring of

metabolic activity of an isolated, perfused rat heart by O/C02 respirometer. Since respirometer provides vital data on consumpbion and production of :1 preserved organ on a continuous basis over a long period of time, it will be possible to use this method to monitor viafiility of not only isolated heart but also any given donor organ under preservation. Key words: ail' organ transplantation isolated heart

INTRODUCTION continuously measuring oxygen consumption and carbon dioxide production by a O/C0e! Respirometer (Micro-Oxymax; Columbus Succe 'S of transplantation of organs depend::; Instruments International Corporation. on the ideal preservation of organs during Columbus, Ohio). tr n port from the donor to the recipient. Hypothermia during transport slow down ATP METHODS 10 s in th excised organs and thcreby keep Hearts are mounted on a fluid perfusion them vi lie for a short period of time. In recent system and perfused through the aorta with years attempts have been made to develop Krebs solution being delivered at a rate of 5 mV methods for long-term prcservation of hearts by min at 37°C by means of a roller pump as hypothermia and cardioplegia (1). Although shown Fig. 1. After 10 min the peristaltic pump hypotherm ia and cardioplegia prolongs is turned off and heart is opened towards air preservation time to 48 hI'S, these conditions delivery system. Fig. 2 is a schematic iUustration have always shown some evidence of myocardial of the air perfusion system. The system consists damage. In order to mitigate such myocardial of a water jacketed heart retention chamber damage, Bailey has preserved guinea pig hearts and airtight lid with two inlet and two outlet by bypoth rmic gas perfusion (2). His study has tubes. One inlet tube is used for cannulation of demonstrated that the combination of the aorta to deliver air through coronary system. hypothermia and 95% oxygen gas perfusion, a One outlet tube withdraws air from the chamber proc dur? known to increase oxygen tension in by means of a teflon pump. The second set of cardiac muscle, ha retained contractile activity in-let and outlet tub s are connected to a Micro­ in guinea pig hearts aftcr 24 hI'S of preservation Oxymax. The outlet tube is used for withdrawing and has not caused any edema. air from the chamber every 60 min for oxygen and carbon dioxide measurements while inlet The prcsent study has been performed to tube returns air sample to the chamber. determine whether rat hearts can be pre erved by air perfusion, instead of 95% O which can 2 RESULTS AND DISCUSSION predispose organs to undergo lipid peroxidation, and whether their viability can be monitored by A total of five hearts have been p rfused

+ orresponding Author I'rc,sent address. *1) partment of Pharmacology, Medical School, Wayne State University. Detroit M1 48202 (U.S.A). *'" olumbus Instruments International Corporation. Columbus OH 43:;:)4 (U.S.Al. 2 4 Venkataraman et al Indian J Physiol Pharmacol 1995; 39(3)

1\1 r Delivery 5 CC/MIN FI 01'1 RAJ inlel

J7'C ~Il WAIER BA"I ~ _02 0'''\1 r I I I~~v:;\·~·~:11 il/\11 I J - ;1 II :, ~--) ...._. _.__ 1

I F1erislollic '------' 11urnp DR,\IN I Iq)f'~' - ~~ (lll ~~oiltli n

Fig. ] Schematic diagram i!lu trating the system for perfusion of physiological salt solution through aorta of an isolated rat hc'lrt.

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5'.4 fMCL L._. _ Fit; 2 Diagrammatic Jllustration of the unit for air perfusion of a smgle rat heart and for m asuremcnts of oxygen consumption and carbon dioxide prQdudion by Mico-Oxymilx. Indian J Physiol Pharmacol 1995; 39(3) Isolated Air Perfused Rat Heart 285 utilising the methods described above. Of these heart, is partly explained by their diminishing five experiment::;, resu}ts of three are taken into contractile activity. A]so, it is possible that low consideration. One took an unusually long time oxygen (20%) used :in this study has not been to transfer the heart from fluid to air system. high enough to provide adequate tIssue oxygen. Another experiment was discontinued halfway Oxygen consumption rises and reaches a due to power failure, peak value of 14 ± 2 ~l/minlg wet weight at After 2~3 hrs of equilibration period, oxygen 15.25 hr. (Fig, 3) This high consumption of consumption by the::;e heart reaches a steady­ oxygen may be due to bacterial growth and/or state 6,25 ± 0.43 lImil1/gm wet weight peroxidation of cellular elements of the dying (mean±SE) between 3-9 hrs. The oxygen heart, In the present study, hearts were not consumption by isolated rat heart at 36°C is excised from the chest cavity under aseptic reported to be 523 ± 47 ~llminlg dry weight or condition and perfusion medium did not contain 105 ± 9 ~l/minJg wet weight, assuming 80% as any antibiotic. Both these precautions with ,vater contents of these hearts (3). It is about purified air through bacterial filters will 18.4';' (the amount calculated for the fluid­ minimise or completely eliminate infection­ perfused-heart! in isolated guinea pig heart induced oxygen consumption. Effects of lower perfused with 95o/r gaseous oxygen (4). Thus, temperature and higher oxygen tension on the low oxygen consumption by the air perfused rat quality of preserved organ can be assessed by heart, which is about 6% of the fluid perfused comparing the oxygen consumption values

02 ConsumpHon 40 r------,

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5

, 0- o 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 28 Time (Hours}

Fig, J , Individual oxygen consumption records from three air perfused hearts during 20 hr preservation period, ~86 Venkataraman et al Indian ,J Physiol Phnrmacol 1995; 39(3) obtained from the respirometer. The system ethane and pentane contents in the chamber air ,;vill allow one to determine whether the by collecting samples from the Micro-Oxymax preserv d organ is deteriorating by lipid after it has completed its me..lsurements of pcroxidation or not by periodically measuring oxygen and carbon dioxide (5) (Fig. 4).

C02 Production 27.5 [ 25 22.5 20 17.5 "'. ./ 15 I I 12.5 ..... //,...... •...... ~~, : 10 ...... ~ . .... ' ,.' ...... ~'-~--- 7.5 ,/",...... 5 .. ' ...... , ..... " -" ...... 2.5

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Fig. 4 Individual carbon dioxide production records from the same three hearts as shown in Fig. :3.

REFERENCES

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;j Rpnlund DG, Lakatta EG, MeJlitis ED, GerstenbIith 5. Dutta S, Muller A. Ishikawa T. Zilllltler 11,'1. Sics A, C. Cakium dependent enhancement of myocardial Alkane production by isolated rat heart and . di lotic lone and energy utilization dissociates systolic Toxicol Letts 1988: 44:55-64