| 1. |
- Malmqvist, Ulf, et al.
(författare)
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Contractile and cytoskeletal proteins in smooth muscle during hypertrophy and its reversal
- 1991
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Ingår i: American Journal of Physiology: Cell Physiology. - 1522-1563. ; 260:5, s. 1085-1093
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Tidskriftsartikel (refereegranskat)abstract
- Hypertrophy of rat urinary bladder smooth muscle was induced by partial urethral obstruction. Bladder weight increased from 70 to 240 mg after 10 days and to 700 mg after 7 wk. Removal of the obstruction after 10 days caused a regression of bladder weight to 130 mg. The relative volume of smooth muscle in the bladder wall increased during hypertrophy. The concentration of myosin in the smooth muscle cells decreased in 10-day hypertrophied bladders, whereas the concentration of actin was unchanged. The actin-myosin ratio was 2.3 in controls, 3.3 in 10-day obstructed bladders, and 2.9 in 7-wk obstructed bladders. After removal of obstruction, the ratio was normalized. Two isoforms of myosin heavy chains were identified (SM1 and SM2). The relative amount of SM2 decreased during hypertrophy. The relative proportion of actin isoforms (alpha, beta, and gamma) was altered toward more gamma and less alpha. These changes were reversible upon removal of the obstruction. Desmin was the dominating intermediate filament protein. The concentration of desmin and filamin increased in the hypertrophic bladders. The increased desmin-actin and filamin-actin ratios in obstructed bladders were normalized after removal of the obstruction. The results suggest that the turnover of contractile and cytoskeletal proteins is fast and can be regulated in response to changes in the functional demands in smooth muscle.
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| 2. |
- Malmqvist, Ulf, et al.
(författare)
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Correlation between isoform composition of the 17 kDa myosin light chain and maximal shortening velocity in smooth muscle
- 1991
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Ingår i: Pflügers Archiv. - 0031-6768. ; 418:6, s. 523-530
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Tidskriftsartikel (refereegranskat)abstract
- The relation between the isoform distribution of the myosin 17 kDa essential light chain (LC17) and the mechanical properties of smooth muscle was investigated. The relative content of the basic (LC17b) and acidic (LC17a) isoelectric variants of the 17 kDa myosin light chain was determined in different mammalian smooth muscle tissues. The relative content of LC17b varied between muscles: rabbit rectococcygeus 0%, rabbit trachea 5%, guinea-pig taenia coli 21%, rat uterus 38%, rabbit aorta 56% and rat aorta 60%. The rate of tension development was determined following photolysis of caged-adenosine triphosphate (ATP) in skinned fibres activated with thiophosphorylation of the regulatory light chains. The half-time for force development was 0.67 s in rabbit rectococcygeus, 1.6 s in rabbit trachea, 1.13 s in guinea-pig taenia coli and 1.38 s in rabbit aorta. The maximal shortening velocity (Vmax) was determined with the isotonic quick release technique in skinned fibre preparations activated with thiophosphorylation. Vmax was 0.25 muscle lengths per second (ML/s) in rabbit rectococcygeus, 0.24 ML/s in rabbit trachea, 0.17 ML/s in guinea-pig taenia coli, 0.11 ML/s in rat uterus and 0.03 ML/s in rabbit aorta. The range of variation in Vmax between muscles was larger than in the half-time for force development. The inverse relationship between Vmax and the relative content of LC17b in the investigated muscles suggests that the type of essential myosin light chain influences the Vmax in smooth muscle.
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| 3. |
- Malmqvist, Ulf, et al.
(författare)
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Cytoskeletal and contractile proteins in detrusor smooth muscle from bladders with outlet obstruction--a comparative study in rat and man
- 1991
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Ingår i: Scandinavian Journal of Urology and Nephrology. - : Informa UK Limited. - 0036-5599 .- 1651-2065. ; 25:4, s. 261-267
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Tidskriftsartikel (refereegranskat)abstract
- Detrusor biopsies were obtained from patients with urinary outlet obstruction due to prostatic enlargement and from age-matched control patients. The relative amounts of actin and myosin and their isoforms, as well as desmin and filamin were determined and compared with corresponding results from bladders from control rats and rats with 10 days of experimental outlet obstruction of the urinary bladder. In the human control detrusor the actin/myosin ratio was similar to that in the control rat. The isoform distribution of the myosin heavy chains differed between man and rat. In the biopsies from the patients with outlet obstruction and in the obstructed rat bladders the actin/myosin ratio was increased. A change in the myosin heavy chain distribution in the obstructed bladders was observed for both species. The filamin/actin ratio increased significantly in the obstructed rat bladders and tended to increase in the obstructed human bladders. Desmin was the dominating intermediate filament protein. The desmin/actin ratio increased in obstructed bladders in man and in rat.
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| 4. |
- Malmqvist, Ulf, et al.
(författare)
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Lactate dehydrogenase activity and isoform distribution in normal and hypertrophic smooth muscle tissue from the rat
- 1991
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Ingår i: Pflügers Archiv. - 0031-6768. ; 419:3-4, s. 230-234
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Tidskriftsartikel (refereegranskat)abstract
- The lactate dehydrogenase (LDH) activity and isoform distribution of LDH were investigated in tissue samples from the rat portal vein, aorta and urinary bladder. In addition, samples were obtained from hypertrophic urinary bladder. The total LDH activity per unit smooth muscle volume was higher in the urinary bladder compared to that in portal vein and aorta. Five LDH isoforms, reflecting different combinations of the two polypeptide chains denoted H and M, could be separated by agarose gel electrophoresis. The aorta contained more of the H form compared to the portal vein and urinary bladder. This difference suggests that the aorta, which is a slow smooth muscle, is more adapted for aerobic metabolism than the faster muscles of portal vein and urinary bladder. In the hypertrophic urinary bladder a shift in LDH isoform pattern towards less of the H form was found, which correlates with a better maintenance of contraction in anoxia in this type of hypertrophic smooth muscle.
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| 5. |
- Malmqvist, Ulf, et al.
(författare)
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Mechanics and Ca(2+)-sensitivity of human detrusor muscle bundles studied in vitro
- 1991
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 143:4, s. 373-380
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical properties of isolated smooth muscle strips from human urinary bladder were investigated in vitro. Bladder tissue was obtained from tumour-free wall regions of bladders from male patients undergoing cystectomy for bladder carcinoma. In intact muscle strips, activated with high-K+ solution, half-maximal force occurred at about 0.9 mM extracellular [Ca2+]. The length-active force relation was determined and the muscle strips were fixed for light and electron microscopy at optimal length for active force (1o). The maximal active force per unit smooth muscle cross-sectional area was 208 +/- 49 mN/mm2, n = 6. Chemically skinned preparations were obtained by treatment with triton X-100. These preparations had a steep [Ca2+]-force relation in the micromolar range which was influenced by calmodulin. The skinned preparations could be maximally activated by irreversible thiophosphorylation of the regulatory light chains. The force-velocity relation was determined in the maximally activated skinned muscle at 22 degrees C at 0.51o. When the muscle was shortened by 10%, force was reduced by 35% whereas the maximal shortening velocity was little affected.
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