Pro-inflammatory cytokines (e.g. interleukin-6) have been implicated in damage associated with cardiopulmonary bypass during open-heart surgery (Zahler et al. 1999). Recent evidence has suggested that catecholamines and interleukin-6 (IL6) may play a role in mechanisms leading to cardiac hypertrophy in the post-ischaemic heart (Burger et al. 2001). Previous studies performed on isolated neonatal rat cardiac myocytes have shown that sympathetic stimulation at supraphysiological levels increases the release of IL6 during reperfusion (Yamauchi-Takihara et al. 1995). In the present study we examined the effect of physiological concentrations (0.1, 1 or 5 ng ml^-1) of noradrenaline (NA) and adrenaline (Adr) on functional recovery and the concentration of IL6 post-ischaemia in the intact rat heart.

Male wistar rats were humanely killed, and the hearts were removed and perfused in the Langendorff mode. Hearts were exposed to 45 min global normothermic ischaemia followed by 60 min reperfusion in the presence and absence of NA or Adr. Left ventricular developed pressure (LVDP) was measured throughout. Enzyme-linked immunosorbent assay was used to measure the concentration of IL6 protein in heart tissue. All results are expressed means ± S.E.M. and analysed using ANOVA with Fischer’s post hoc test (PLSD). n ²ge³ 3.

In the absence of any drug, ischaemia resulted in 43 % recovery in LVDP. Reperfusion with NA resulted in no recovery but treatment with Adr (1 ng ml^-1) produced a 95 % recovery (P < 0.05 versus control). Ischaemia and reperfusion caused no change in IL6 protein with 2.504 ± 0.176 pg ml^-1 µg^-1 in the perfusion control and 2.619 ± 0.116 pg ml^-1 µg^-1 with reperfusion. There was an increase in the presence of Adr to 4.242 ± 0.729 pg ml^-1 µg^-1 (P < 0.01) when reperfusing with Adr.

This work shows that NA and Adr have differential effects on recovery following an ischaemic insult. Adr significantly improved functional recovery, which was associated with increased levels of IL6 in the rat heart. Whether the production of IL6 contributes to protection requires further investigation.