title: Structure and mechanics of growing arterial microvessels from hypertrophied urinary bladder in the rat.
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 (Lmax). 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 Lmax from 134 +/- 5 microns to 222 +/- 19 microns; (ii) an increase of the media thickness from 22.4 +/- 1.9 microns to 32.2 +2- 3.0 microns; (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 alpha 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.
authors.affiliation: Department of Physiology and Biophysics, Lund University, Sweden.
authors.forename: P J
authors.initials: PJ
authors.lastname: Boels
authors.forename: A
authors.initials: A
authors.lastname: Arner
authors.forename: U
authors.initials: U
authors.lastname: Malmqvist
authors.forename: B
authors.initials: B
authors.lastname: Uvelius
mesh_terms: D000818:Animals; D001160:Arterioles / Q000473:pathology / Q000503:physiopathology; D002217:Carbachol / Q000494:pharmacology; D005260:Female; D006651:Histocytochemistry; D006984:Hypertrophy / Q000473:pathology; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D024510:Muscle Development; D009131:Muscle, Smooth, Vascular / Q000254:growth & development / Q000473:pathology* / Q000503:physiopathology; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000502:physiology; D001743:Urinary Bladder / Q000098:blood supply / Q000254:growth & development / Q000473:pathology*; D001745:Urinary Bladder Diseases / Q000473:pathology* / Q000503:physiopathology
chemical_list: D010656:Phenylephrine; D002217:Carbachol; D011188:Potassium