MEMBRANE POTENTIAL AND TENSION IN GUINEA-PIG URETER

¹ Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi

The ureter, void of the renal end, showed no spontaneous action potential and was suitable for study of roles of steady depolarization as well as of action potential in tension development. Action potentials resulted in phasic contractions, whereas K⁺-induced sustained depolarizations brought about tonic contractions. The magnitude and duration of the tonic contraction could be reduced by removal of glucose or Ca²⁺, Li⁺ substitution for Na⁺, or addition of 2,4-dinitrophenol or Mn²⁺. Membrane potentials at 80 mM K⁺ level under these modified conditions were close to the control value determined in unmodified 80 mM K⁺ Tyrode's solution. The tension level was indirectly affected by the magnitude of sustained depolarization in guinea-pig ureter.

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