Abstract
1. 1. In seven poikilotherm species, i.e. cyclostome, Myxine glutinosa; teleosts, Gadus morrhua; Platichtys flesus; amphibia, R. pipiens; R. temporaria; Xenopus laevis; reptiles, Vipera berus. Ca paradox could not be obtained in ventricular strips at 8–12°C. 2. 2. In similar preparations from human atria at 30°C and 37°C, Ca paradox was obtained similarly as in other homoiotherms. 3. 3. In homoiotherms, lowered temperature (below 30°C) has a protective effect. Viper myocardium did not display Ca paradox at 12, 22 or 32°C, whereas human myocardium displayed Ca paradox even at 30°C. 4. 4. It is postulated that the absence of Ca paradox in poikilotherms is not due to the low temperature. 5. 5. In hagfish ( Myxine glutinosa) the absence of Ca paradox seems to be due to the specific conditions concerning Ca exchange in the myocardial cell (large glycocalyx).
Published Version
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