Smooth muscle energetic in the pig coronary artery during a calcium-dependent and a calcium-independent isometric contraction.
Heat production by resting smooth muscle, was measured with a heat-flux micro calorimeter on cut-open segments of pig coronary artery superfused at 30 degrees C, was 0.93+/-0.06 (n=16) mW/g wet weight. Time courses of the increases in isometric tension and heat production with respect to basal during sustained supra maximal acetylcholine stimulation were qualitatively similar: initial peak tapering down to a supra basal plateau. Mean tension-associated heat production over 1 h was 0.16 J/g. During sustained exposure to phorbol 12,13-dibutyrate, supra basal tension and--with a 5-10 min initial delay--supra basal heat progressively increased to a plateau in about 40 min. Mean tension-associated heat production over 1 h was only 0.02 J/g with normal extracellular and intracellular mobilizable Ca2+ pools, and it was further reduced to 0.01 J/g with depleted Ca2+ pools. These results show that the maintenance--if not necessarily the building up--of tension under phorbol 12,13-dibutyrate does not entail any large dissipation of energy and is not dependent on the presence of normal Ca2+ pools.
Beny
J L
JL
University Department of Physiology, Geneva, Switzerland.
van der Bent
V
V
Decrouy
A
A
Chinet
A
A
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002151:Calorimetry; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism*; D004734:Energy Metabolism; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D013552:Swine
D015240:Phorbol 12,13-Dibutyrate; D000109:Acetylcholine; D002118:Calcium