Abstract
1. The intravenous lethal dose of ouabain for the guinea pig, expressed per kilogram body weight, decreases by about 25 per cent between birth and maturity.
2. The lethal dose of ouabain for the isolated and continuously reperfused heart of the guinea pig, expressed per gram of heart, decreases by more than one-half between the age of three weeks and maturity.
3. The intensity of the metabolic response of slices of guinea pig heart muscle to ouabain increases progressively between birth and maturity. In order to produce a given change in oxygen consumption at birth the concentration of the drug has to be several times higher than in maturity.
4. The sensitivity of the guinea pig and of isolated guinea pig heart muscle to ouabain does not change significantly during adult life.
5. The lethal dose of ouabain for the isolated heart of the adult female guinea pig does not differ significantly from that for the heart of the adult male.
6. The doses and concentrations of ouabain required in vivo and in vitro have been compared. Possible mechanisms of the increase in the sensitivity of guinea pig myocardium to ouabain during growth have been discussed.
Footnotes
- Received December 10, 1952.
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