Coronary Flow Response to Vasodilators in Isolated Hearts Cold Perfused for One Day with Butanedione Monoxime

Inhibition of Na(+)/H(+) isoform-1 exchange protects hearts perfused after 6-hour cardioplegic cold storage

OBJECTIVES

Cardiac ischemia-reperfusion activates Na(+)/H(+) exchange; excess Na(+) and the resulting Ca(2+) overload, through reverse Na(+)/Ca(2+) exchange, cause cellular injury and cardiac dysfunction. We postulated that inhibiting the Na(+)/H(+) isoform-1 exchanger would add to the protection of hearts after long-term cold storage in acidic cardioplegic solution.

METHODS

Guinea pig hearts were isolated and perfused at 37 degrees C with Krebs-Ringer's solution (KRS) and then switched to an acidic St. Thomas solution (STS) at 25 degrees C. Perfusion was stopped at 10 degrees C, and hearts were stored for 6 hours in STS at 3.4 degrees C. On reperfusion to 25 degrees C, hearts were perfused with KRS for 60 minutes. Hearts were divided into 4 groups: sham control (SHAM); eniporide (EPR, EMD96785) IV, 1 mg/kg given IV over 15 minutes before heart isolation; EPR intracoronary, 1 micromol/liter in STS given intracoronary after heart isolation; and EPR IV and intracoronary.

RESULTS

Values at 60 minutes reperfusion (the percentage of control [100%] before cold storage) are given, respectively, for EPR IV, EPR intracoronary, and EPR IV and intracoronary vs drug-free SHAM (SEM, *p < 0.05 vs SHAM): 72% +/- 3%*, 65% +/- 3%*, and 81% +/- 2%* vs 55% +/- 3% for left ventricular pressure; 94% +/- 3%*, 96% +/- 5%*, and 102% +/- 2%* vs 81% +/- 3% for coronary flow; 60% +/- 2%, 58% +/- 3%, and 74%* +/- 3% vs 58% +/- 4% for cardiac efficiency; 106% +/- 2%*, 108% +/- 3%*, and 107% +/- 2%* vs 116% +/- 4% for percentage of O(2) extraction. Infarct size as percentage of ventricular weight was 20% +/- 3%*, 31% +/- 3%, and 6% +/- 2%* vs 35% +/- 3% (SHAM) after 60 minutes of reperfusion.

CONCLUSIONS

Na(+)/H(+) isoform-1 exchanger inhibition, particularly if given IV before storage and intracoronary during cooling and rewarming, adds to the protection of cardioplegic solutions.

Effects of L-arginine and N omega-nitro-L-arginine methyl ester on cardiac perfusion and function after 1-day cold preservation of isolated hearts

BACKGROUND

Coronary flow responses to endothelium-dependent (acetylcholine [ACh] or 5-hydroxytryptamine [5-HT]) and endothelium-independent (adenosine [ADE] or nitroprusside [NP]) vasodilators may be altered before and after 1-day hypothermia during the perfusion of arginine vasopressin (AVP), D-arginine (D-ARG), L-arginine (L-ARG), or nitro-L-arginine methyl ester (L-NAME).

METHODS AND RESULTS

Four groups of guinea pig hearts (37.5 degrees C [warm]) were perfused for 6 hours with AVP, L-ARG, L-NAME, or nothing (control). Five heart groups (cold) were perfused with AVP, D-ARG, L-ARG, L-NAME, or nothing (control), but after 2 hours they were perfused at low flow for 22 hours at 3.7 degrees C and again for 3 hours at 37.5 degrees C. ADE, butanedione monoxime, and NP were given for cardioprotection before, during, and after hypothermia. In warm groups, L-ARG did not alter basal flow or ADE, ACh, 5-HT, or NP responses, whereas L-NAME and AVP reduced basal flow and the ADE response, abolished ACh and 5-HT responses, and increased the NP response. In cold groups after hypothermia. L-ARG did not alter basal flow, but L-NAME, AVP, D-ARG, and control reduced flow. In the postcold L-ARG group, ACh increased peak flow, but NP did not increase flow in other cold groups. Effluent L-ARG and L-CIT in the cold control group fell from 64 +/- 9 and 9 +/- 1 micrograms/L at 1 hour to 36 +/- 5 and 5 +/- 1 micrograms/L at 25 hours, respectively. Left ventricular pressure and cardiac efficiency improved more in the postcold L-ARG group than in the postcold D-ARG, AVP, and L-NAME groups.

CONCLUSIONS

Endogenous effluent levels of L-ARG and L-CIT decrease after 24 hours in isolated hearts, whereas perfusion of L-ARG improves cardiac performance, basal coronary flow, and vasodilator responses. In contrast, L-NAME, L-ARG, and AVP limit flow and performance but maintain a partial vasodilatory response to NP. Sustained release of NO may account for improved performance after L-ARG after hypothermia.