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

inexpensive. Briefly in this model, right atrial tissue is sliced and then nourished and
oxygenated in an organ bath using the principles of superfusion. The model has vet to be
characterised and the aim of this chapter is to investigate the stability of the human right
atrium when incubated in a buffered media, its response to various degrees of ischaernic
insult and the short and prolonged effects of reoxygenation.
2.2 Tissue slices
Cardiac muscle cells are relatively small compared to skeletal muscle cells, so it is
possible to slice myocardium without cutting more than a small proportion of them,
especially if the slices are cut parallel to the long axis of the myocytes. With thin slices
(0.2 -0.5 mm), vascular integrity are not required to support viability and metabolic
function [2371. However, because oxygen and substrate supplies are derived from
diffusion, the thickness of the slice is critical. It must be sufficiently thin to allow 02 to
diffuse to Its center at the rate required to maintain aerobic metabolism.
2.3 Preparation of atrial slices
Specimens of human right atrium appendage were obtained from patients undergoing
elective heart surgery. During surgery, the right atrial tissue is routinely removed for
venous cannulation and establishment of cardiopulmonary bypass. Samples were quickly
immersed in cold (4'C) Krebs-Henseleit-HEPES medium which comprised (in mM)ý
NaCl (118), KCI (4.8), NaHC03 (27.2), KH2PO4 (1), MgC12 (1.2), CaC12 (1.25), Glucose
(10), HEPES (20). The medium was pre-bubbled with 95% 02/5% C02 to attain a P02 OF
25-3OkPa and pH 7.4. The atfial appendage was immediately sliced free hand with
36