A novel videomicroscopic technique for studying rat ureteral peristalsis in vivo

Existing techniques do not allow analyzing the fine movements of the ureteral wall during in vivo peristaltic contractions. A videomicroscopic technique has been developed to study the active mechanical displacements of the rat ureter.

The middle portion of the ureter in a length of 16-18 mm was elevated from its base by microsurgical preparation, encased in a specific tissue chamber and continuously superfused with physiological saline. Contractions were recorded by videomicroscopy. A number of characteristic points on the surface were identified by the pattern of vasa vasorum. Their movements were analyzed in a coordinate system defined by the axial and radial directions of the segment. Identified surface points on the ureter moved along characteristic trajectory loops during contractile cycles.

In addition to the synchronized longitudinal and circumferential contractions, typical axial displacement cycles could be identified. Our observations demonstrate that longitudinal contractions might be more important in transporting the urine as thought earlier because of the axial tether of the ureter.

(1) A longitudinal contraction ring preceding the circumferential one axially distends the distal segments. (2) Initial phase of the longitudinal contraction ring promotes bolus volume rearrangement toward the passive diameter dilation. (3) Longitudinal contraction with the maximum circumferential contraction ring just behind it helps pushing the urine bolus downward. (4) Ureteral segments proximal to the longitudinal contraction ring will be passively axially stretched which also helps their filling.