Chemical energetics of force development, force maintenance, and relaxation in mammalian smooth muscle.

Abstract

High-energy phosphate utilization (A~P) associated with force development, force maintenance, and relaxation has been determined during single isometric tetani in the rabbit taenia coli. ATP resynthesis from glycolysis and respiration was stopped without deleterious effects on the muscle. At 18~ and a muscle length of 95% 10, the resting rate of energy utilization is 1.8 + 0.2 nmol/g,s -1, or 0.85 _+ 0.2 mmol ~P/mol of total creatine (Ct).s -1, where Ct = 2.7 ~mol/g wet wt. During the initial 25 s of stimulation when force is developed, the average rate of'A~P was -8.2 + 0.8 mmol/mol Ct.s -1, some four times greater than during the subsequent 35 s of force maintenance, when the rate was -2.0 ztz 0.6 mmol ~P/tool Ct.s -1. The energy cost of force redevelopment (0 to 95% P0) after a quick release from the peak of a tetanus is very low compared with the initial force development. Therefore, the high rate of energy utilization during force development is not due only to internal work done against the series elasticity nor to any high rate of cross-bridge cycling inherently associated with force development. The high economy of force maintenance compared with other muscle types is undoubtedly due to a slower cross-bridge cycle time. The energy utilization during 45 s of relaxation was not statistically significant, and fPdt/A~P was higher during relaxation than during force maintenance in the stimulated muscle.

Mechanical transformations of living cavitary bodies

“…Some in vitro observations show that the myosin head of a smooth muscle is much more efficient than that of a skeletal muscle (VanBuren et al, 1994). This phenomenon is more often explained by longer periods of cross-bridge attachment to actin filaments in smooth muscle cells (Siegman et al, 1980;Dillon and Murphy, 1982;Murphy, 1994;Guilford et al, 1997;Butler et al, 2001).…”

Obstruction-induced alterations within the urinary bladder and their role in the pathophysiology of lower urinary tract symptomatology.

“…56 Adequate cytosolic ATP concentration is maintained by anaerobic metabolism of glucose to pyruvate and subsequent oxidative metabolism of pyruvate to CO 2 and H 2 O within the mitochondria through the tricarboxylic acid (TCA) cycle and respiratory chain pathway. 57 CS is the rate-limiting enzyme of the TCA cycle, which provides substrates for the respiratory chain. A reduction in respiratory chain substrates would lead to decreased oxidative phosphorylation (i.e., decreased ATP synthesis).…”

Metabolic factors influencing lower urinary tract function

“…Effective bladder and urethral function is not only dependent on the integrity of autonomic innervation, but is also intimately related to intracellular metabolism (Paton, 1967;Rohner et al 1967;Hellstrand & Vogel, 1985;Haugaard et al 1987;Levin et al 1987Levin et al , 1988Levin et al , 1989aWendt & Gibbs, 1987;Wendt, 1989;Arner et al 1990, 1993Lin et al 1992;Polyanska et al 1993). Although there is an extensive information base relating cellular metabolism to vascular smooth muscle function (Casteels & Wuytak, 197.5;Siegman et al 1980;Butler & Siegman, 1982;Davidheiser et al 1984;Paul et al 1987;Paul, 1989;Scott & Coburn, 1989), relatively little is known regarding cellular metabolism and lower urinary tract smooth muscle function.…”

“…Rabbit bladder behaved similarly (Zhao et al 1991;Bilgen et al 1992b;Kwon et al 1996). ATP provides most of the energy required to maintain cell function (Casteels & Wuytak, 1975;Siegman et al 1980;Butler & Siegman, 1982;Paul, 1989). The cytosolic ATP level is maintained by combined anaerobic metabolism of glucose to pyruvate, and oxidative metabolism of pyruvate to CO, and H,O within the mitochondria (Lehninger, 1973;Nicholls & Ferguson, 1992).…”

“…Cytosolic ATP levels are maintained by combined anaerobic metabolism of glucose to pyruvate, and oxidative metabolism of pyruvate to CO, and H,O within the mitochondria (Casteels & Wuytak, 1975;Siegman et al 1980;Butler & Siegman, 1982;Davidheiser et al 1984;Paul et al 1987;Paul, 1989;Bilgen et al 1 9 9 2~) .…”