Increased calcium sensitivity of chemically skinned human atria by myosin light chain kinase.
We investigated the influence of myosin P-LC phosphorylation catalysed by calcium/calmodulin-dependent myosin light chain kinase (MLCK) on the tension-pCa relation of chemically skinned human atrial fibres. MLCK-induced increased myosin P-LC phosphorylation sensitized human atrial skinned fibres for calcium by 0.11 pCa-units in patients with valvular heart disease, and by 0.05 to 0.07 pCa-units in patients with coronary heart disease. The MLCK effect could be antagonized by a light chain phosphatase. The protein phosphatase ocadaic acid (OA) had no influence on the tension-pCa relation of skinned human atrial fibres and had no potentiating effect together with MLCK. The MLCK preparation used in this study was from bovine ventricle and revealed a KM of 1.8 x 10(-5) M and a Vmax of 822 nmol Pi/min/mg using purified bovine ventricular myosin-LCs as substrate.
Morano
I
I
II. Physiologisches Institut, Heidelberg, F.R.G.
Bächle-Stolz
C
C
Katus
A
A
Rüegg
J C
JC
D002118:Calcium / Q000502:physiology*; D004988:Ethers, Cyclic / Q000494:pharmacology; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism*; D006331:Heart Diseases / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009200:Myocardial Contraction / Q000187:drug effects; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism / Q000494:pharmacology*; D009218:Myosins / Q000378:metabolism*; D019319:Okadaic Acid; D010766:Phosphorylation
D004988:Ethers, Cyclic; D019319:Okadaic Acid; D009219:Myosin-Light-Chain Kinase; D009218:Myosins; D002118:Calcium