Concentrations and contractile effects of substance P in the human ampullary‐isthmic junction

Abstract

From 20 women undergoing hysterectomy, strip preparations were isolated from the outer, longitudinal and the inner, circular smooth muscle layer of the ampullary-isthmic junction (AIJ), together with small arterial segments dissected as ring preparations from the root of the mesosalpinx. The specimens were mounted in organ baths and isometric tension was recorded. In addition, tissue concentrations of substance P (SP) in the ampulla, AIJ and utero-tubal junction were determined by radioimmunoassay. Tissue concentrations of SP expressed as pmol X g tissue-1 (wet weight, +/- SE) amounted to 3.09 +/- 1.40 in the utero-tubal junction, 1.08 +/- 0.299 in the AIJ and 0.742 +/- 0.299 in the ampulla. In strips of circular muscle, SP at concentrations of 10(-7) -3 X 10(-6) mol X l-1 elicited a combined phasic and tonic response and in longitudinal muscle a mainly tonic contraction was produced. In both tissues, contractions elicited by SP were rapidly abolished in calcium-free medium. Nifedipine abolished the phasic contraction elicited in circular muscle by SP while the tonic response was resistant. The contraction in longitudinal muscle was reduced by 20-30%. Vasoactive intestinal polypeptide (VIP) decreased tension in preparations contracted by SP, prostaglandin F2 alpha and K+-depolarization (124 mmol X l(-1). In unstimulated oviductal arterial preparations, SP had no effect, while the peptide induced a transient relaxation of noradrenaline contracted preparations, and slightly decreased tension of K+-depolarized vessels. The results suggest that SP may be involved in the control of motility of the human AIJ.