Metabolism of Detrusor Smooth Muscle in Normal and Obstructed Urinary Bladder

Abstract

The detrusor smooth muscle cells are arranged in bundles of various directions, diameters and lengths (Gabella and Uvelius, 1990). In the rat roughly 85 per cent of a bundle is occupied by smooth muscle cells (Arner, Malmqvist and Uvelius, 1990), the remainder of the bundle constitutes the intercellular space, containing e.g. collagen fibrils. Non-muscle cells are rare but occasional fibroblasts can be found. The blood supply to the urinary bladder is mainly through the superior vesical arteries originating from the internal iliac arteries. The corresponding veins run in parallel with the arteries. In the rat the major intramural vessels are situated in the connective tissue between the epithelium and the muscle. Capillaries are found between but not in the muscle bundles (Gabella and Uvelius, 1990). The distance for diffusion of oxygen and energy substrates from the capillaries to the smooth muscle cells and for waste products from the muscle cells to the capillaries is thus considerable. The extracellular space would be expected to restrict the rate of diffusion within the bundle for hydrophilic substances.