Microvascular preconditioning is not detectable by corrosion casting in the isolated perfused rat heart after 30 minutes of ischaemia

Figures & data

Table I.  Heart Rate (beats.min⁻¹)–mean±SD.

		Experimental stage
Group	Protocol	Pre-ischaemia	p	Post-ischaemic reperfusion
1	Ischaemia	171±21		–
2	Ischaemia with 60 min reperfusion	170±10	0.47	166±11
3	Ischaemia + preconditioning	179±12		–
4	Ischaemia + preconditioning with 60 min reperfusion	167±10	0.80	165±14^a

p<0.05 regarded as significant.

^ap vs. Group 2 = 0.97.

Table II.  Coronary flow rates (ml.min⁻¹)–median [interquartile range].

		Experimental stage
Group	Protocol	Pre-ischaemia	p	60 mins Post-ischaemic reperfusion
1	Ischaemia	14 [10–17]		–
2	Ischaemia with 60 min reperfusion	10 [9–17]	0.99	14 [11–15]
3	Ischaemia + preconditioning	14 [14–24]		–
4	Ischaemia + preconditioning with 60 min reperfusion	13 [9–18]	0.94	13 [11–18]

p<0.05 regarded as significant.

Table III.  Post-ischaemic Capillary density (mm³mg⁻¹) – median [interquartile range].

Treatment	Not preconditioned	p	Preconditioned
Ischaemia only	5.2 [2.6–7.1]	0.13	6.8 [4.0–14.7]
	p = 0.0003		p = 0.0018
Reperfused	16.0 [10.2–23.0]	0.47	20.7 [10.7–22.8]

Kruskal-Wallis with Dwass-Steel-Chritchlow-Fligner multiple comparison procedure It can be seen that preconditioning did not improve matters, either during the ischaemic challenge, or after reperfusion. p < 0.05 regarded as significant.

Further analysis showed: ischaemia only vs. the preconditioning effect: p = 0.18 (unpaired t-test) and p = 0.31 (Mann-Whitney); for reperfused ventricles p = 0.67 (unpaired t-test) and p = 0.94 (Mann-Whitney).

Figure 1.  Langendorff perfusion for 30 minutes followed by ischaemia for 30 minutes; not reperfused. Note the irregularity of the luminal diameter as well as gaps in the architecture and flattening of the capillary lumen consistent with that seen in previous studies 14, 17.

Figure 2.  30 minutes pre-ischaemic Langendorff mode perfusion followed by warm ischaemia for 30 minutes and then Langendorff mode reperfusion for 60 minutes. Note the more regular luminal diameters although the surface of the cast material is somewhat roughened. Gaps in the capillary architecture are still apparent.

Figure 3.  30 minutes of pre-ischaemic Langendorff mode perfusion, then three ischaemic preconditioning cycles, followed by 30 minutes of warm ischaemia. Not reperfused. Note similarity of findings to Figure 1, indicating a lack of protective effect.

Figure 4.  Langendorff perfusion for 30 minutes followed by three ischaemic preconditioning cycles. Then: 30 minutes of warm ischaemia (as in Figure 3) followed by reperfusion in Langendorff mode for 60 minutes. A few similarities are seen to Figure 2 like the roughened endothelial surface. Architectural defects persist although the capillaries are less flattened. This is consistent with previous studies 14, 17.

Glyn MC, Lawrenson JG, Ward BJ. A Rho-associated kinase mitigates reperfusion-induced change in the shape of cardiac capillary endothelial cells in situ. Cardiovasc Res. 2003; 57: 195–206

 PubMed Web of Science ®Google Scholar

Chaudhry MA, Belcher PR, Day SP, Muriithi EW, Wheatley DJ. Erythrocyte-containing versus crystalloid cardioplegia in the rat: Effects on myocardial capillaries. Ann Thorac Surg. 2003; 75: 890–8

 PubMed Web of Science ®Google Scholar