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

Abstract

ABSTRACT. A high-K + , Na + -deficient (I-154 K + ) solution induced contraction followed by gradual relaxation of the smooth muscles of the bovine trachea, while hyperosmotic addition of 65 mM KCl induced a large sustained contraction. Exposure of the muscle to the I-154 K + solution induced an increase in the ratio of cellular water content and a sustained increase in oxidized flavoprotein fluorescence or reduced pyridine nucleotide fluorescence. The I-154 K + solution also induced a sustained increase in [Ca 2+ ]i level. Decreases in developed tension and increases in cellular water content were both prevented by the addition of sucrose or NaCl but not pyruvate. Substitution of KI for KCl in the I-154 K + solution produced a greater inhibition of contraction, while substitution with K-propionate produced no inhibition of contraction. Moreover, decreases in developed tension and increases in cellular water content were both prevented by addition of 100 µM 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), but not 10 µM bumetanide or 1 mM acetazolamide. In conclusion, I-154 K + solution induced-relaxation in the bovine trachea may be due to swelling of smooth muscle cells and the mechanism of swelling is probably involved in DIDS-sensitive anion movement.

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

“…In the present experiment, we attempted to clarify the inhibitory mechanism of Na ] i ) level, and compare to our previous data in bovine trachea [7]. Moreover, we measured phosphocreatine (PCr) and ATP contents in the porcine and bovine trachea.…”

“…Recently, we showed that I-154 K + solution induced-relaxation of bovine trachea is probably due to swelling of cells [7]. These data indicate that, only in the trachea, the mechanisms of high-K + , Na + -deficient solution-induced relaxation are different depending on species.…”

“…Figure 1A solution was applied to the muscle, muscle tension increased and then decreased to 20.5  3.6% at 120 min (Fig. 1A), it was significantly smaller than that of bovine trachea (31.3  4.9% [7] ). These data were similar to those obtained in bovine trachea [7].…”

“…Moreover, the inhibition of glucose utilization in I-154 K + medium in porcine trachea is different from that of bovine trachea. Application of hyperosmotically-added high-K + solution induced a sustained contraction, while an isosmotically-substituted high-K + , Na + -deficient solution induces contraction followed by gradual relaxation in various smooth muscles [5][6][7][15][16][17][18][19][20][21]. The possible mechanism of these decreases in muscle contractility of tonic muscle is swelling of the cells, as in rabbit aorta [19].…”

“…In some experiments, sucrose (50 mM), NaCl (50 mM), pyruvate (5.5 mM) and oxaloacetate (5.5 mM) were added to PSS. The concentration of those substances was followed by our previous reports [5,7,[15][16][17][18].…”