RU 12. Ultrastructure and calcium overload on the pathophysiological change in partial unilateral ureteral obstruction

Objective: To study the pathophysiological changes and motion mechanisms after ureteral obstruction by detecting the free Ca²⁺ concentration and changes in mitochondria ultrastructure in ureteral smooth muscle cells of rats with partial unilateral ureteral obstruction (PUUO).

Methods: 80 male Wistar rats were randomized into 4 groups: 8-week PUUO group; 16-week PUUO group; two control groups in the same age; 20 rats in each group. We established PUUO animal models by implanting the top half of the left ureter to psoas major muscle in PUUO groups, and isolated left ureter in controls. 8 and 16 weeks later after model establishment respectively, we removed ureters, isolated single smooth muscle cells from ureter, used fluorescent probe Fura- 2/AM to detect the concentration of free Ca²⁺ in smooth muscle cells, and observed the changes in mitochondria ultrastructure.

Results: Fluorescence ratio imaging of static smooth cell intracellular Ca²⁺ showed: the concentration of intracellular Ca²⁺ in 8-week PUUO group had no significant difference with that of controls; it was noted from the electron microscope that in 8-week experimental group, mitochondria increased and assembled, without significant in volume; the intracellular Ca²⁺ concentration in 16-week PUUO group was significantly higher, with statistical significance noted (P<0.05), mitochondria in 16-week experimental group grew larger and became round, with shallower groundplasm and vacuolization.

Conclusions: Chronic ureteral obstruction impairs the mitochondria ultrastructure and affects the function of calcium pump, leading to calcium overload; the overload further damages and disturbs the structure and function, decreasing contractility of ureteral smooth muscle.