Effect of Sulfanilamide on the Isolated Frog Heart

Abstract

A study was made of the effects of sulfanilamide on the isolated frog heart using the Straub-Fuehner method. The solutions of sulfanilamide used ranged from 0.05% to 0.50% and were made up in frog heart Ringer's. This solution was used between sulfanilamide per fusions to return the heart to normal.

All concentrations caused an increase in amplitude, more marked in the higher concentrations. In the weaker dilutions, the rate was only slightly increased, followed by depression, whereas the stronger solutions all caused a depression of rate. Further observations were made with stronger solutions of sulfanilamide, up to 0.8%, essentially with the same results. The heart always stopped in diastole. This was not due to the weight of the lever, since it also stopped in diastole when wholly disconnected from the lever.

In order to determine if any part of the action of sulfanilamide was caused by a change in pH, both the Ringer's solution and the 0.5% solution of sulfanilamide in Ringer's were tested. The sulfanilamide raised the pH very little so that the solution was still within the pH range permissible for frog heart Ringer's. Therefore, it was not a change in pH which affected the heart.

The effect of sulfanilamide on the isolated frog heart is stimulation followed by depression. The stimulation increases the amplitude. The effect is transient, however, and often lasts only 10 minutes although, in some cases, it persists as long as 20 or 30 minutes. The maximum increase occurs with a 0.25% solution. The rate may also be slightly increased but it is the amplitude that shows the greatest effect of stimulation. On the other hand, the secondary depression appears as a decreased rate.