We hypothesize that the phosphorylation of HSP20 is instrumental in the inhibition of vascular smooth muscle contraction. Contractile events of two different vascular smooth muscles, bovine carotid artery smooth muscle (BCASM) and human umbilical artery smooth muscle (HUASM), were examined in a muscle bath. Phosphorylation changes were measured with whole cell phosphorylation and two dimensional gel electrophoresis. Serotonin (5HT, 1 uM, 22) produced contraction of both BCASM (6.17±0.68 g) and HUASM (3.04±0.38 g). Preincubation with isobutyl-2-methylxanthine (IBMX, 1 mM)/forskolin (FSK, 10 uM) for ten minutes completely inhibited 5HT (1 uM, 22) induced contraction in BCASM (0.20±0.00 g), but not in the HUASM (3.90±2.15 g). Whole cell phosphorylation results (fold increase over control +/- SEM, * = p < 0.05 HUASM vs. BCASM, N.D. = not detectable, n = 3-5) were: 5HT (22) IBMX/FSK (102) + 5HT (22) HSP20 BCASM isoform pI 6.0 1.81±1.21 N.D. isoform pI 5.9 1.14±0.53 13.75±3.47* isoform pI 5.7 1.16±0.83 5.35±0.72* HUASM isoform pI 6.0 N.D. N.D. isoform pI 5.9 0.99±0.45 2.15±0.11* isoform pI 5.7 N.D. N.D.* In BCASM, IBMX/FSK+5HT inhibits contraction and produces increases in the phosphorylation of HSP20 (7-fold) and myosin light chains (MLC20) (1.76±0.53 foc). In HUASM, pretreatment with IBMX/FSK+5HT was associated with minimal changes in HSP20 phosphorylation and increased MLC20 phosphorylation (1.90±0.10 foc) with contraction. These data suggest that increases in HSP20 phosphorylation and not decreases in MLC20 phosphorylation modulate the inhibition of contraction.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology