INCREASED CA2+ AND MYOSIN PHOSPHORYLATION, BUT NOT CALMODULIN ACTIVITY IN SENSITIZED AIRWAY SMOOTH MUSCLES

被引:31
作者
JIANG, H [1 ]
RAO, K [1 ]
LIU, XL [1 ]
LIU, G [1 ]
STEPHENS, NL [1 ]
机构
[1] UNIV MANITOBA, FAC MED, DEPT PHYSIOL, WINNIPEG, MB R3E 0W3, CANADA
关键词
HYPERRESPONSIVENESS; MYOSIN LIGHT-CHAIN KINASE; MYOSIN LIGHT-CHAIN PHOSPHORYLATION; INTRACELLULAR CALCIUM; CALCIUM SENSITIVITY;
D O I
10.1152/ajplung.1995.268.5.L739
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
The increased shortening velocity and capacity of airway smooth muscle (ASM) from ragweed pollen-sensitized dogs, which may be responsible for its in vivo airway hyperresponsiveness, have been shown to be associated with higher actomyosin adenosinetriphosphatase activity and greater level of phosphorylation of the 20-kDa myosin light-chain (MLC(20)) at rest and during contraction. Current studies show that the elevated level of phosphorylation may be the result of an increased myosin light-chain kinase (MLCK) activity due to excessive quantity of MLCK. There were no significant changes in total activity of calmodulin, a protein that binds and activates MLCK, in sensitized dog ASM (SASM) compared with control ASM (CASM). When normalized to the relative calmodulin content in the tissues, the specific calmodulin activities (means +/- SE) in sensitized tracheal smooth muscle (STSM) and sensitized bronchial smooth muscle (SBSM) and in their controls were not different (STSM 0.359 +/- 0.117, CTSM 0.339 +/- 0.136, SBSM 0.201 +/- 0.098, and control bronchial smooth muscle 0.213 +/- 0.056 nmol P-i . calmodulin content(-1). min(-1), respectively). Intracellular Ca2+ levels indicated by fura 2 fluorescent dye remained unaltered in SASM. We conclude that airway hyperresponsiveness may result from higher MLCK content in SASM rather than from changes in Ca2+-calmodulin activities, which is an example of alteration in Ca2+ sensitivity of ASM.
引用
收藏
页码:L739 / L746
页数:8
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