Effects of High-K+, Na+-Deficient Solution on Contractility of the Smooth Muscles of the Porcine Trachea

Abstract

ABSTRACT. A high-K + , Na + -deficient (isosmotic 154 mM K + and 0 mM Na + ; I-154 K + ) solution induced contraction followed by gradual relaxation of the smooth muscles of the porcine trachea, while hyperosmotic addition of 65 mM KCl (H-65 K + ) induced a large sustained contraction. The I-154 K + solution also induced a sustained increase in [Ca 2+ ] i level. Decreases in muscle tension and increases in cellular water content were both prevented by the addition of sucrose or NaCl in the porcine trachea. An additional application of phloridzin inhibited recoveries of I-154 K + solution by addition of NaCl in the porcine trachea. Addition of pyruvate or oxaloacetate recovered the I-154 K + solution-induced relaxation in the porcine trachea. Although application of I-154 K + solution did not affect PCr and ATP contents in the bovine trachea, the solution induced a gradual decrease of PCr content in the porcine trachea. Moreover, application of pyruvate or oxaloacetate recovered the I-154 K + solution-induced decreases of PCr content in the porcine trachea. Phloridzin inhibited H-65 K + -induced contraction in porcine, but not in bovine trachea. In conclusion, the I-154 K + solution-induced relaxation in the porcine trachea is probably due to swelling of cells and inhibition of glucose utilization. Moreover, the inhibition of glucose utilization in I-154 K + medium in porcine trachea is different from that of bovine trachea.

Hypertonic saline inhibits airway smooth muscle contraction by inhibiting Ca2+ sensitization

“…To determine the potential dehydration effect of HS on ASM, the water content of ASM following exposure to HS was measured as described previously, with some modifications. Briefly, trachea ASM was treated by PSS or HS at 37°C for 15 minutes and blotted dry on filter paper and weighed using a balance.…”

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

“…On the other hand, application of an isosmotically substituted high K + , Na + -deficient solution induces contraction followed by gradual relaxation in various smooth muscles. The possible mechanisms of the relaxation are classified as three types: (1) swelling of the cells as in rabbit aorta [29], guinea pig trachea [26] and bovine trachea [12]; (2) inhibition of glucose uptake as in guinea pig urinary bladder [26] and guinea pig ileum [25]; and (3) the combination of swelling of cells and inhibition of glucose uptake as in guinea pig gallbladder [26], guinea pig tenia coli [6, 31] and porcine trachea [13]. Thus, these reports suggest that SGLTs play an important role in contraction of phasic muscle, such as urinary bladder and tenia coli.…”

“…Phloridzin, an inhibitor of SGLT, decreases high K + -induced contraction, in guinea pig tenia coli, a phasic muscle [28], but not in bovine trachea, a tonic muscle [13]. Moreover, phloridzin does not affect the contraction induced by high K + solution containing pyruvate instead of glucose physiological salt solution (PSS) in guinea pig tenia coli [28].…”