Mechanical and biochemical events during hypoxia-induced relaxations of rabbit aorta.
Hypoxic relaxation of norepinephrine contractions of isolated rabbit aorta is rapid, whereas relaxation of KCl contractions is slower and blunted. The data given here suggest that with receptor-evoked contractions of rabbit aorta, the energy-limitation of ATP-dependent K+ channels and other sarcolemmal channels, myosin light chain kinase, and actin-activated myosin ATPase are probably not involved in oxidative energy-contraction coupling. The data strongly support the hypothesis that the rate limiting, energy-dependent step is upstream to myosin light chain kinase, which is 50% inhibited at an ATP concentration of about 0.5 mM. This energy-dependent step may be in the inositol phospholipid transduction system, as we have previously postulated (Coburn et al., 1988). In contrast the energy-limited reaction during KCl contractions appears to be the actin-activated myosin ATPase which is 50% inhibited at a mean ATP concentration of about 0.1 mM.
Moreland
S
S
Department of Pharmacology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543.
Coburn
R F
RF
Baron
C B
CB
Moreland
R S
RS
D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism / Q000502:physiology; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004734:Energy Metabolism / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D009126:Muscle Relaxation / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000503:physiopathology*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010084:Oxidation-Reduction; D010725:Phosphocreatine / Q000378:metabolism; D011817:Rabbits
D000199:Actins; D007295:Inositol Phosphates; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D009219:Myosin-Light-Chain Kinase; D000251:Adenosine Triphosphatases; D009218:Myosins