Endocrinology · 1952 · 63 citations · 0 references
MedicineEndocrinologyPhysiologyReproductive BiologyReproductive EndocrinologyReproductive PhysiologyEndocrine PhysiologyGonadal EndocrinologyMammalian EndocrinologyOvarian FunctionOvarian PhysiologyUterine ContractilityCardiac Muscle ContractionMyometrial ContractionOvarian Hormone PhysiologyOvarian HormonesSmooth Muscle ContractionStaircase FormationUterine Contraction PatternsUterine Smooth Muscle Physiology
THE “staircase” phenomenon is well known to be exhibited by cardiac muscle, but has not been established as characteristic of smooth muscle. As the present paper will demonstrate, the staircase phenomenon readily occurs in experiments on rabbit uterine muscle. Its occurrence has a certain uniformity if the muscle is taken from animals that are in similar condition with respect to the ovarian hormones. If, however, the hormonal status of the animal is varied, the form of the staircase is altered in a way highly characteristic of the dominant ovarian hormone. Unlike earlier studies on the staircase phenomenon our experiments have utilized isometric rather than isotonic recording, inasmuch as the former method has been shown to yield more accurate quantitative results (Hajdu and Szent-Györgyi, 1952). The contractions were not only elicited, as in previous studies, by a series of stimuli at constant frequency after a period of rest, but also by varying the frequency of stimulation in a steady state (Dale, 1932).