REGULATION OF ISOMETRIC FORCE AND ISOTONIC SHORTENING VELOCITY BY PHOSPHORYLATION OF THE 20,000 DALTON MYOSIN LIGHT CHAIN OF RAT UTERINE SMOOTH-MUSCLE
REGULATION OF ISOMETRIC FORCE AND ISOTONIC SHORTENING VELOCITY BY PHOSPHORYLATION OF THE 20,000 DALTON MYOSIN LIGHT CHAIN OF RAT UTERINE SMOOTH-MUSCLE
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DOI：
10.1007/bf00584103
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发表时间：
1985-01-01
影响因子：
4.5
通讯作者：
HATHAWAY, DR
中科院分区：
文献类型：
--
作者：
HAEBERLE, JR;HOTT, JW;HATHAWAY, DR
通过磷酸化20，000道尔顿的肌球蛋白L链来检测K-去极化大鼠子宫平滑肌的等长收缩力维持和等张缩短速度的调节。肌球蛋白L链（LC 20）磷酸化在收缩20 s（0.46 mol PO 4/mol LC 20）时出现短暂峰值后，磷酸化在收缩2 min（0.28 mol PO 4/mol LC 20）时下降至稳态，收缩2-90 min时无显著变化。等长力发展得更慢，在2分钟时达到最大值，到90分钟时没有进一步的变化。轻负荷（0.1 F0）缩短速度如LC 20磷酸化，在收缩20秒时最初增加到0.034 L0/s的峰值，然后在2分钟时下降到0.023 L0/s。4-从2分钟时的0.023 L0/s增加到90分钟时的0.006 L0/s。细胞外Ca减少的分级激活与稳态等长力和LC 20磷酸化的比例变化相关。缩短的速度也减少了钙，但是，不像LC 20磷酸化的速度发生在低水平的发达国家的力量最大的变化。与在90分钟收缩期间观察到的缩短速度的大幅降低（其中力和LC 20磷酸化不变）相反，尽管力和LC 20磷酸化均显著（> 3倍）降低，但在分级激活下未发生缩短速度的类似降低。在子宫平滑肌等长收缩过程中，除L链磷酸化外的其他因素也参与了等张缩短速度的调节。
The regulation of isometric force maintenance and isotonic shortening velocity by phosphorylation of the 20,000 dalton L chain of myosin was examined for K-depolarized rat uterine smooth muscle. Following a transient peak in myosin L chain (LC20) phosphorylation at 20 s of contraction (0.46 mol PO4/mol LC20), phosphorylation declined to a steady-state by 2 min (0.28 mol PO4/mol LC20) with no significant change from 2-90 min of contraction. Isometric force developed more slowly, reaching a maximum at 2 min with no further change out to 90 min. Lightly-loaded (0.1 F0) shortening velocity like LC20 phosphorylation, increased initially to a peak of 0.034 L0/s at 20 s of contraction and then declined to 0.023 L0/s by 2 min. Unlike LC20 phosphorylation and isometric force, shortening velocity decreased .apprx. 4-fold from 0.023 L0/s at 2 min to 0.006 L0/s at 90 min of contraction. Graded activation with reduced extracellular Ca was associated with proportional changes in steady-state isometric force and LC20 phosphorylation. Shortening velocity was also decreased with reduced Ca, however, unlike LC20 phosphorylation the greatest changes in velocity occurred at low levels of developed force. In contrast to the large reductions in shortening velocity observed during 90 min contractions where force and LC20 phosphorylation were unchanged, similar reductions in shortening velocity did not occur with graded activation in spite of significant (> 3-fold) decreases in both force and LC20 phosphorylation. Factors other than L chain phosphorylation are involved in the regulation of isotonic shortening velocity during extended isometric contractions of uterine smooth muscle.