In this study of normal adult human and ovine ureters, a characteristic distribution of a large population of typical mast cells was described by light and electron microscopy. Pharmacological studies were used to ascribe a functional role for these cells in normal and pathological states. In the structural investigations typical mast cells with their cytoplasm packed with characteristic electron dense granules were found in close vicinity to smooth muscle cells. A close association between mast cells and a fibroblast like La-cell and non myelinated nerve fibers was noted. The prevalence of mast cells was higher in human ureters. Human and sheep ureteral ring preparations exhibited spontaneous rhythmical contractions in vitro. Addition of histamine (10(-6)-10(-5) M) induced an increase in the frequency of contractions and enhanced the basal tone particularly in human samples. It is likely that histamine under pathological conditions such as renal colic and inflammatory reactions is released from mast cells within the ureter and induces a state of forceful contractions and pain fibre stimulation.
Isolated sheep and human ureteral preparations (from patients with bilharzia) were subjected in-vitro to graded elongation and the effect on tension and spontaneous peristaltic frequency was assessed. Sheep specimens were obtained from three locations: the intra- and extrarenal portion of the pelvis and distal ureter. Elongation (stretch) induced an increase in spontaneous frequency only in pelvic ureteric specimens, but not in the distal ureter. Basal tension increased exponentially with stretch and most markedly in the distal sheep ureter and also in human preparations. Active tension (amplitude of phasic contractions) increased with stretch in specimens from all locations and reached a maximum at 110-115% elongation. These data suggest that acute distension of the ureter increases frequency of peristaltic waves only in the intrarenal parts of the ureter. Acute obstruction in renal colic can induce hypermotility in terms of increased frequency and force of contraction.
Evidence of a leaky urothelial barrier in bilharzial uropathy is presented. The ultrastructural basis of this concept is demonstrated together with its functional consequences. The study was conducted on 4 ureters obtained at surgery from patients with non-functioning kidneys due to chronic bilharzial infections. Six normal ureters from kidney donors served as controls. Light and electron microscopic studies showed a reduced thickness of the transitional epithelium together with localised disruption of intercellular junctions and infiltration of red blood cells. The functional studies involved in vitro demonstration of stable phasic peristaltic contractions which were fundamentally altered by the addition of urine. The changes in motility included increase in contractile frequency and elevation of basal tone, inducing a state of hypermotility which could be equated with ureteric spasm. These changes were partly reversible upon administration of the histamine l-blocker, mepyramine. Evidence is presented to show that these changes might be induced in vivo by histamine released from mast cells triggered by urine leaking through a damaged urothelial barrier. The functional consequences (pain, spasm) are discussed.
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