Ultrastructural changes in the obstructed pig detrusor: A preliminary report

Abstract

Interest in using the pig to study the effects of urinary tract obstruction on the kidney has been established for some time. The present study was intended as a pilot investigation to find out whether or not structural changes in the detrusor occur in a chronic obstructive pig model. Because of the pilot nature of the study, and the high cost of purchase and maintenance of pigs, it was limited to one normal and one obstructed animal. Obstruction was created by allowing a young pig to grow for 7 weeks with an inactive inflatable urethral cuff in place. Samples from the bladder body detrusor were obtained from this and from a normal pig. These were then processed for electron microscopy by standard procedures. Multiple sections of each sample were examined and photographed to determine the structural status of muscle cells, the width of intercellular spaces and the relative area of muscle cell junctions. In samples from the obstructed pig, we found (1) no evidence of degeneration or regeneration of muscle cells; (2) hypertrophy of detrusor muscle cells; (3) widening of intercellular spaces (from 237 nm in the normal to 503 nm in the obstructed pig); (4) intercellular deposits of basal lamina-like material; and (5) reduction of junctional sarcolemmal area relative to total sarcolemmal area as well as total muscle cell volume. All morphometric data were statistically significant. The observed reduction of muscle cell junctional area may be a "dilution" effect secondary to muscle cell hypertrophy, and/or represent a true loss of junctions. Despite the small sample size, our fidings suggest that ultrastructural obstructive detrusor changes occur and indicate the need for further investigation to define the scope and chronologic evolution of these changes.

Morphometry of the obstructed detrusor: I. Review of the issues

“…Based on our thorough review of the literature (see Part I1 [Meyer and Elbadawi, 1989]), it became obvious that most methods used previously for smooth muscle morphometry yield meaningful results only if a sufficient number of longitudinally and/or cross-sectioned cells are available for study. Cells so sectioned can readily be obtained with careful orientation of tissue blocks from the intestine (where the muscle cells are aligned as one longitudinal and one transverse layer) or arteries (where all muscle cells are aligned in the same direction).…”