title: Myosin isoform expression and force generation in cultured resistance arteries.
abstract: Organ culture of mesenteric resistance arteries results in a loss of force-generating ability, which is prevented by 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We have tested the hypothesis that the culture-induced decrease in active stress is associated with altered myosin isoform expression. Rat mesenteric resistance arteries were studied immediately (fresh) or after incubation at 37 degrees C for 48 h in culture medium (control), with 300 pg/ml 1,25(OH)2D3, or with 5 microg/ml insulin. Isometric force was measured by myography; myosin heavy chain (MHC) and regulatory myosin light chain isoform (MLC) contents were determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Maximal active stress to 100 mM K+ (mN/mm2) was greater for fresh (147.8 +/- 4.9) than control (109.2 +/- 4.6, P = 0.001) or insulin (79.6 +/- 8.6, P < 0.001) but not 1,25(OH)2D3 (137.4 +/- 9.5, P = 0.197). Organ culture did not alter MLC or MHC smooth muscle (SM)-1 isoform content. MHC SM-2 content (nmol/mg protein) was greater in fresh (0.038 +/- 0.003) than control (0.026 +/- 0.003, P = 0.012) and insulin (0.027 +/- 0.002, P = 0.018) but not 1,25(OH)2D3 (0.036 +/- 0.003, P = 0.693); nonmuscle MHC (NMM) was observed in insulin. The maximal active stress response to K+ significantly correlated with SM-2 MHC isoform content (r2 = 0.483, P < 0.001). We conclude that 1) arterial organ culture alters MHC isoform content, 2) SM-2 MHC isoform content positively correlates with active stress generation, 3) 1,25(OH)2D3 maintains force-generating capacity by preventing the shift of MHC isoform expression, and 4) insulin impairs force-generating ability by lowering MHC SM-2 content and stimulating NMM expression.
authors.affiliation: Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555-1065, USA.
authors.forename: K
authors.initials: K
authors.lastname: Ishibashi
authors.forename: R D
authors.initials: RD
authors.lastname: Bukoski
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology*; D009218:Myosins / Q000378:metabolism*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D014655:Vascular Resistance; D014661:Vasoconstriction
chemical_list: D009218:Myosins; D002117:Calcitriol