Freezing preservation of the mammalian cardiac explant V. Cryoprotection by ethanol

Abstract

We studied the colligative cryoprotective effect of ethanol (EtOH) in preserving the isolated rat heart frozen at −3.4 °C or unfrozen at −1.4 °C. Addition of 4.7% ( v v ) EtOH to a cardioplegic solution, CP-14, raised the osmolality from 280 to 1100 mOsm/kg H 2O and lowered the melting point from −0.52 to −2.1 °C. Freezing of the cardiac explant at −3.4 °C for 6 h resulted in 34.3 ± 1.9% of the tissue water as ice; recovery of cardiac output (CO) was 50%. Polyethylene glycol, which at 5% ( w v ) has been shown to cryoprotect the hearts during freezing at −1.4 °C, did not improve the protective effect of 4.7% EtOH. CP−14 + 4.7% EtOH did not freeze at −1.4 °C. After 6 h storage, CO in hearts flushed with CP-14 + 4.7% EtOH oxygenated with 95% O 2/5%CO 2 returned to almost control level and was much higher than that in hearts flushed with 100% O 2 saturated-CP−14 + 4.7% EtOH. Storage of 8 and 12 h reduced CO to 87 ± 9 and 60 ± 5% of control. By employing EtOH as a colligative cryoprotectant, we preserved the adult mammalian heart frozen at −3.4 °C or unfrozen at −1.4 °C, suggesting that this small molecular weight, penetrating substance may be a suitable cryoprotectant for long-term storage of the cardiac explant at high subzero temperatures.