The effects of a temperature below 15 degrees C on the myocardial calcium and ultrastructure in donor heart preservation in a canine model

Protective effects of calpain inhibitor for prolonged hypothermic cardiac preservation

PURPOSE

For successful organ transplantation, it is important to properly preserve the donor organ. This study was carried out to investigate tissue damage generated by the activation of calpain during prolonged hypothermic cardiac preservation using specific antibodies for mu- and m-calpain proenzymes, and to ensure the protective effect of calpain inhibitor 1 (N-acetyl-leucyl-leucyl-norleucinal).

METHODS

Excised rat hearts were divided into two groups: in Group I, the heart was arrested and immersed in University of Wisconsin solution with 20 microM of calpain inhibitor 1 (n = 28) and in Group N, the heart was arrested and immersed in University of Wisconsin solution without calpain inhibitor (n = 27). After a 12-hour preservation period at 4 degrees C, the hearts were reperfused on an isolated perfusion apparatus. Separation of the myocardial calpain isozymes was carried out by DEAE cellulose chromatography and both calpain proenzymes were detected by immunoblotting.

RESULTS

The cardiac function was more satisfactorily maintained in Group I in comparison with Group N. Remarkable leakage of creatine kinase, glutamic-oxaloacetic transaminase and lactate dehydrogenase was detected in Group N, while it was efficiently suppressed in Group I. During ischemia, mu-calpain proenzyme decreased in Group N (p < 0.01), but there was no significant change in m-calpain. However, during reperfusion, both mu- and m-calpains decreased more in Group N (p < 0.01).

CONCLUSION

Activation of calpain proenzymes and a decrease in cardiac function during preservation and reperfusion were demonstrated. The use of calpain inhibitor to protect against tissue damage was suggested as being useful for the prolonged preservation of the heart.

The effect of calcium on hypothermia-facilitated resuscitation of warm ischemic kidney tissue slices: a role for the mitochondrial permeability transition pore?

This study examined the effect of varying the calcium (Ca) content of a solution used for aerobic hypothermic storage of rabbit kidney cortex tissue slices previously injured by 1-h warm ischemia. Ischemic slices were stored in UW Na-gluconate solution for 18 h at 5 degrees C with 0.5, 1.5, or 1.75 mM Ca (+/- quinacrine; 100 microM) followed by warm (37 degrees C) aerobic incubation in physiologic buffer for 3.5 h to simulate reperfusion. There was no effect of solution Ca concentration on tissue ATP (adenosine 5'-triphosphate) and nonesterified fatty acid (NEFA) content during reperfusion. However, recovery of slice ATP and NEFA content to control levels was seen with addition of quinacrine to hypothermic storage medium containing either 1.5 or 1.75 mM Ca but not with 0.5 mM Ca storage medium. Treatment of tissue slices with cyclosporine A (20 microM), an inhibitor of the mitochondrial Ca-induced permeability transition pore, abolished the resuscitative benefits of hypothermic preservation with quinacrine + 1.5 mM Ca. These results suggest that quinacrine exerts its effects on warm ischemic tissue during hypothermic storage via the mitochondrial permeability transition pore. An effect utilizing a pore-open state is probable but it remains unclear if quinacrine acts on the pore directly or gains access to the matrix space through the pore and exerts its effects via an unknown mechanism. These results indicate that resuscitative hypothermic storage methods may be able to use manipulation of the permeability transition pore as a valuable adjunct to pharmacologic treatments administered during hypothermia.

Effect of the potassium-channel opener nicorandil as an adjunct to cardioplegia on myocardial preservation in isolated rabbit hearts

We studied the effect of nicorandil on the hemodynamic, biochemical, and ultrastructural changes in rabbit hearts (n = 50) rendered cardioplegic with a single injection of Bretschneider's HTK solution over 30 min or 60 min at 37 degrees C or 15 degrees C, followed by reperfusion at 37 degrees C for 60 min. Particular attention was focused on the aspects of dose-response relationship, temperature sensitivity, and ischemic tolerance. Isolated hearts were prepared for modified Langendorff circulation using modified Krebs-Henseleit bicarbonate solution bubbled with a 95% O2(-5)% CO2 gas mixture, to which nicorandil (0, 0.1, 1, and 5 mM) was added. The optimal concentration of nicorandil was 1mM, which increased the recovery of left ventricular (LV) function, affecting coronary flow and the myocardial cyclic adenosine monophosphate, but not the myocardial concentrations of adenine nucleotide compounds or total calcium. These effects were abolished by the addition of glibenclamide to the HTK, but they were not diminished by a high potassium (K+) concentration of 20mM. The addition of nicorandil 1mM to the HTK at 15 degrees C did not improve the recovery of LV function. Our result suggested that nicorandil used adjunctly prevents LV functional depression after 30min, and possibly 60min of cardioplegia at 37 degrees C, and that this effect is not disturbed by a high K+ concentration up to 20 mM. However, nicorandil has temperature sensitivity whereby it loses its efficacy at 15 degrees C.