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

The stability of the preparation is also reflected by the profile of LDH leakage, an
index widely accepted as a marker of tissue damage 11261. In both instances there
was a small but gradual leakage into the incubation media that at first sight could be
interpreted as indication of some on-going tissue injury, however, albeit this cannot
be completely ruled out, it is most probably due to a physiological transmembrane
movement of proteins and enzymes [ 128,2 101. The massive LDH leakage observed
at the end of 48 hr of incubation supports the argument that significant tissue
damage has occurred by this time.
A number of factors including the temperature of the media in which the atrial tissue
is collected and processed, the slice thickness and the P02 of the incubation media
may affect the viability of the preparation. In preliminary studies (data not shown)
we observed that all these factors play an important role in maintaining the stability
of the preparation and that for this to be achieved the temperature of the media for
the collection of the specimen should be 4- 1 O'C, recovered and processed at about
37'C, the thickness of the slices should not be more than 0.5 mm and the P02 of the
media should be 25-30 kPa. These findings are supported by Paradise el (It [237]
and Prasad el aL [2461 who report that the thickness of the muscle and the P02 of the
media are determinants of the oxygen diffusion rate and the viability of the
preparation. The small and not statistically significant reduction in tissue viability
seen after the initial 30 min equilibration period associated with an elevated LDH
leakage is possibly the result of mechanical injury sustained during the sectioning of
the tissue. The possibility that ischaemic injury maybe a contributor to this
phenomenon is unlikely because the procedure is carried out under hypothermic
conditions and the time spent in processing the tissue samples is under 2 min, a time
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