Related Experiment Video
Updated: Aug 14, 2026

Physiological Preparation of Hair Cells from the Sacculus of the American Bullfrog (Rana catesbeiana)
Published on: March 17, 2017
Effects of tonicity on the resting tension in bullfrog ventricle
Introduction:
A study of the effects of hyper -and hypotonic media on resting tension were examined in ventricular muscle of the bullfrog was undertaken because only few studies on resting tension from the viewpoint of E-C coupling in the heart muscle are available.
Materials And Methods:
Thin strips obtained from the bullfrog ventricle were perfused in the sucrose-gapped chamber, which allowed the effective stimulation and the simultaneous measurement of the contractile tension and the intracellular membrane potential.
Results And Conclusions:
Hypertonic solutions up to 3.0 T, prepared by adding NaCl or sucrose, induced a triphasic response, namely an initial rapid decline, a secondary slow development of contracture and a final transient off-contraction. Both the second and the final responses were strongly sensitive to the calcium concentration of the bathing medium and were completely abolished by depleting external calcium ions. The initial decreasing phase was not sensitive to external calcium but was progressively augmented by increasing the initial muscle length, whereas the dehydration process, estimated by measuring the muscle weight, was unaffected by muscle stretch. The changes in the membrane potential were not essential for these responses. It was concluded that the initial tension decline results from the passive process due to volume change while the sustained contracture as well as the transient off-contraction are produced by some active process involved in E-C coupling. Hypotonic solutions induced a monophasic contracture which is insensitive both to the external calcium concentration and muscle stretch. The possible mechanism for the genesis of the response was discussed.
Related Concept Videos
Tonicity in Animals
Tonicity in Plants
The Resting Membrane Potential
Resting Membrane Potential
The Inside of a Neuron is More Negative
The membrane potential of a cell can be measured by inserting a microelectrode into a cell and comparing the charge to a reference electrode in the extracellular fluid. The...
Tonicity in Plants
Tonicity
Tonicity describes the capacity of a cell to lose or gain water depending on the solute...
Tonicity in Animals

