ALTERATIONS IN CIRCULATING CYCLIC GUANOSINE-MONOPHOSPHATE (C-GMP) DURING SHORT AND LONG ISCHEMIA IN PRECONDITIONING

The trim of this study was to investigate if levels of circulating cyc lic guanosine monophosphate (c-GMP) alter in preconditioning. Twenty-e ight rabbits were divided into four groups. In vivo hearts were precon ditioned, either with 5 min (group A, n = 8) or with 1 min (group B, n = 8) ischemia, followed by 10 min reperfusion, while groups C (n = 7) and D (n = 5) had no interventions. Protection was determined by subj ecting groups A, B and C (but not D) to 30 min regional ischemia which was followed (including group D) by 2 h reperfusion. Seven blood samp les were collected for the assessment of circulating c-GMP at differen t points of time. All results were expressed in pmol/ml using radio-Im munoassay and the infarcted to risk area in percent using fluorescent particles and tetrazolium chloride (TTC). Circulating c-GMP increased during long ischemia only in group A (baseline value 47 +/- 4, long is chemic values 60.5 +/- 4 and 60.4 +/- 4, p < 0.05). Circulating c-GMP in group A was significantly higher in the middle of the long ischemia in comparison to the groups B, C and D (60.5 +/- 4 vs 43.9 +/- 4, 45. 8 +/- 5 and 43.6 +/- 4, p < 0.05). Infarcted to risk ratio was lower i n group A than in groups B and C (12.2 +/- vs 29.6 +/- 6 and 34.2 +/- 6 respectively, p<0.05). Circulating c-GMP is increased in classically preconditioned in comparison to ineffectively preconditioned hearts o r to control groups. This elevation may be related to the protective e ffect of this phenomenon.