Key Role of Glycogen Storage in High K⁺-Induced Contraction of the Smooth Muscles of the Bovine Trachea

Abstract

ABSTRACT. To elucidate the role of glycogen in the contraction of tracheal smooth muscle, we investigated the changes in the glycogen contents of the bovine trachea during contractions induced by high K + and hypoxia (achieved by bubbling N 2 instead of O 2 ), either in a glucose-free condition or in the presence of iodoacetic acid (IAA), an inhibitor of glycolysis. Hyperosmotic addition of 65 mM KCl (H-65 K + ) induced a sustained contraction. A glucose-free condition did not affect H-65 K + -induced contraction. However, hypoxia slightly inhibited the contraction, and glucose-free PSS with hypoxia or IAA remarkably inhibited the H-65 K + -induced contraction. H-65 K + induced a sustained increase in reduced pyridine nucleotide (PNred) fluorescence, representing glycolysis activity. Hypoxia alone slightly enhanced PNred fluorescence, and when combined with a glucose-free condition, it remarkably enhanced the H-65 K + -induced PNred fluorescence. IAA inhibited PNred fluorescence. In the presence of H-65 K + , a glucose-free condition, hypoxia and the combination of glucose-free PSS and hypoxia decreased the glycogen contents. However, IAA had no effect on glycogen contents. Although hypoxia or glucose-free PSS did not affect PCr and ATP contents, the combination of hypoxia and glucose-free PSS or IAA induced a gradual decrease of PCr content. In conclusion, we suggest that endogenous glycogen was utilized to increase the activity of glycolysis for maintaining high K + -induced contraction of the bovine trachea in the glucose -free and/or hypoxic condition.

Aerobic metabolism on muscle contraction in porcine iris sphincter

“…These results are consistent with a study by Ishida and Paul (1990) [6] on taenia coli, suggesting that aerobic metabolism is involved in the contractile response of porcine iris sphincter muscles. Recently, we demonstrated that muscle contraction in porcine urinary bladder, a phasic muscle, depends on aerobic metabolism [9], but not in bovine trachea, a tonic muscle [8]. Our present data more suggest that contraction of phasic muscles depends on aerobic metabolism rather than that of tonic muscles.…”

“…In contrast, hypoxia has little effects on the contraction of elastic vascular smooth muscles, such as those in the aorta and carotid arteries [1, 13]. Hypoxia also slightly reduces high K + -induced contraction of smooth muscles of the bovine trachea [8]. …”

Effects of hypoxia and glucose-removal condition on muscle contraction of the smooth muscles of porcine urinary bladder

“…These reports suggest that aerobic metabolism-dependent muscle contraction is high in the phasic type smooth muscle, such as the taenia coli and uterus. In contrast, hypoxia slightly inhibited high K + -induced contraction in the bovine trachea [ 11 ]. Moreover, the hypoxia slightly inhibited high K + -induced contraction in the rabbit aorta [ 4 ].…”

“…In contrast, glucose-free PSS did not influence the maintenance of contraction in the porcine carotid artery [ 17 ] and rabbit aorta [ 20 ]. In bovine trachea smooth muscle (tonic muscle), glucose-free PSS did not affect the maintenance of high K + -induced contraction [ 11 ]. Glucose-free PSS decreased contraction of the tonic component to muscarinic agonists and high K + rather than the phasic component in the urinary bladder of the rabbit [ 16 ] and guinea pig [ 23 ].…”

Phloridzin inhibits high K⁺-induced contraction via the inhibition of sodium: glucose cotransporter 1 in rat ileum

“…PCr and ATP contents in the muscle strips were measured using HPLC as reported previously [14]. Muscle strips were incubated with PSS for 30 min and contracted by H-65K + .…”