Abstract
Rat bladder hypertrophy, induced by a partial ligation of the urethra, was used to study the accompanying changes of microvascular smooth muscle mechanics, pharmacology and morphology. A segment of a microarterial vessel to the bladder was taken from a defined anatomical location and studied in a wire myograph in vitro at the length for maximal isometric force development (L max). After 10 days of ligation, bladder hypertrophy resulted in a microvascular growth response compared to non-operated controls which was characterized by (i) an increase of the calculated diameter at L max from 134±5 μm to 222±19 μm; (ii) an increase of the media thickness from 22.4±1.9 μm to 32.2±3.0 μm; (iii) an increase of the active tension from 1.42±0.28 mN/mm to 3.06±0.33 mN/mm; (iv) no change of the wall/lumen ratio (from 0.83±0.10 to 0.79±0.15). Normalized length/force relations (active, passive and total) did not differ significantly between microarteries from control and hypertrophic bladders. Microvascular smooth muscle growth was also associated with a decreased sensitivity to K+-induced depolarization and an increased sensitivity to α 1-adrenergic stimulation. No differences were noted regarding the Ca2+ sensitivity of force during K+-induced depolarization. The results suggest that microvascular growth (1) is immediately and positively influenced by the organ growth; (2) results in a functional resetting of the microvascular segments towards larger diameters without gross morphological or mechanical alterations; and (3) is accompanied by pharmacological alterations of the smooth muscle reactivity.
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Boels, P.J., Arner, A., Malmqvist, U. et al. Structure and mechanics of growing arterial microvessels from hypertrophied urinary bladder in the rat. Pflügers Arch. 426, 506–515 (1994). https://doi.org/10.1007/BF00378528
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DOI: https://doi.org/10.1007/BF00378528