Contractile behaviour of the human pyelo-ureteral musculature. I. Contraction frequency/force relationship

405 normal and pathological ureteral and pyelic strips were electrically stimulated according to different schemes. Reflux strips produced stronger contractions than normal ones; transversally excised strips contracted stronger than longitudinal ones. The amplitude of a test pulse after a series of stimuli increased with increasing delay until a constant value (at 30 s). The first contraction after a rest period had a lower latency and higher amplitude ("rest contraction"). The time to peak force of contractions was constant. Elongation of the strips increased the amplitude but not the latency of the contractions. In the discussion the similarities between the contractile behaviour of the pyeloureteral muscle and of the heart are discussed.