On the cardiac efficacy of helveticosol-3',4'-di-nitrate, a new glycoside.

The cardiac and extracardiac effects of a new glycoside, helveticosol-3',4'-di-nitrate (HdN), were compared with those of helveticosol (H) and helveticosol-3',4'-di-propionate (HdP) in isolated guinea-pig heart preparations, in volunteers and dogs. In the atrium and heart, HdN produces positive inotropic effects at the same concentrations as H and at 10 times lower concentrations than HdP. In the heart, the difference between equieffective concentrations of HdN and HdP is smaller, but this is true only for the concentration required to produce the maximum inotropic effect. In the anaesthetized dog equieffective cardiac effects are obtained after oral admiinistration of the glycosides in the ratio 1 : 2 : 0.5 (HdN : HdP : H). After administration of HdN and HdP at equal ratios, no significant differences were observed between the toxic effects in conscious dogs or in the extent of shortening of STI in volunteers. Replacement of the hydrophobic subsituent propionate for the more hydrophilic nitrate residue causes slight changes in cardiac efficiency.