Microvascular preconditioning is not detectable by corrosion casting in the isolated perfused rat heart after 30 minutes of ischaemia.
OBJECTIVE
Ischaemic preconditioning protects the myocardium from ischaemic injury and may also protect the vascular endothelium from the deleterious effects of ischaemia and reperfusion. We examined the possibility that ischaemic preconditioning might preserve the integrity of the coronary microcirculation following ischaemia and reperfusion.


METHODS
Isolated rat hearts were perfused in Langendorff mode for 30 minutes and then subjected to 30 minutes of global ischaemia with or without ischaemic preconditioning (threexthree minute cycles). Some hearts underwent an additional 60 minutes of reperfusion. At the end of each protocol, microvascular corrosion casts were made by methylmethacrylate injection.


RESULTS
Median left ventricular capillary density [interquartile range] after ischaemia was slightly but not significantly better with preconditioning at 6.8 [4.0-14.7]x10(-2) mm3.mg(-1) vs. 5.2 [2.6-7.1]x10(-2) mm3.mg(-1) (p=0.13). After 60 min of reperfusion, capillary density in preconditioned left ventricles was 20.7 [10.7-22.8]x10(-2) mm3.mg(-1) vs. 16.0 [10.2-23.0]x10(-2) mm3.mg(-1) for untreated ventricles (p=0.47). Coronary blood flow and heart rate were unchanged from before ischaemia.


CONCLUSIONS
Ischaemia for 30 minutes induced global left ventricular capillary loss which was unmodified by preconditioning. We did not demonstrate vascular preconditioning using this model.
Arangannal
A
A
Division of Cardiovascular Sciences, University of Glasgow, Glasgow, Scotland, UK.
McGarrity
A
A
Wheatley
D J
DJ
Belcher
P R
PR
D000818:Animals; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000503:physiopathology / Q000648:ultrastructure*; D016319:Corrosion Casting; D004195:Disease Models, Animal; D006339:Heart Rate; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D008833:Microcirculation / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D017202:Myocardial Ischemia / Q000473:pathology* / Q000503:physiopathology / Q000628:therapy; D015428:Myocardial Reperfusion Injury / Q000473:pathology* / Q000503:physiopathology / Q000517:prevention & control; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors