Effect of Potassium on the Mechanical Activity of Taenia Coli, Uterus and Portal Vein of the Guineapig

Abstract

The effect of solutions containing 5 9 to 127 mmol.1h' potassium on the mechanical activity of taenia coli, uterus and portal vein of the guinea-pig was investigated using isometric and isotonic recording in vitro. In the taenia coli at 370C an increase of the K+-concentration from 5 9 (Krebs' solution) to 6-4 or 6 9 was sufficient to elicit mechanical activity. Maximal contractures were obtained with about 24 mmol. -1-K+, both with isometric and isotonic recording (in the latter case with loads ranging between 1 and 7 g). With higher K+-concentrations the contractures were not greater or were slightly smaller. In the taenia coli at 37.C the isometric contractures were well maintained (up to 15 min) when obtained with 20-40 mnmol. 11 K+. With higher K+-concentrations the tension declined after 30-60 s, the more noticeably the higher the K+-concentration. At 18°-21°C the decline in tension during K+-stimulations started earlier in time, occurred with lower K+-concentrations, and was more noticeable. However, even at 15°CK+-concentrations of about 22-30ummol.1-1 produced contractures maintained up to 15 min. Isotonic contractures were always better maintained than isometric contractures. Solutions containing over 25 mmol.l1-K+ produced at 37°C an initial transient relaxation of the taenia coli, which was abolished by tetrodotoxin but not by guanethidine or atropine; it was also present after the adrenergic fibres had been destroyed by 6-hydroxy-dopamine. It is suggested that this relaxation is due to stimulation of non-adrenergic inhibitory nerves. A transient relaxation was also observed when the K+-concentration was raised during a spontaneous contraction or during stimulation with carbachol. In the uterus maximal contractures were obtained with K+-concentrations of 20-30 numol.l1-; smaller contractures were obtained with higher K+-concentrations. With K+-concentrations up to 45 mmol.1-' the isometric contractures were well maintained; with higher K+-concentrations they declined within 30-90s. Isotonic contractures were better maintained than isometric contractures. In taenia coli and uterus after stimulation with solutions containing more than 50 mmol.lI-K+ upon re-introduction of the Krebs' solution there were powerful contractions (after-contractions) which lasted longer the higher the K+-concentration had been. In the portal vein the isotonic contractures were approximately proportional to the K+-concentration.It has been known at least since the work of Ringer [1883] that bathing a muscle in a solution containing potassium and calcium ions is sufficient to induce mechanical activity. In skeletal muscle (frog semitendinosus) the the smallest K+-concentration which produces a detectable tension is about 20 mmol. 1 -' [Hodgkin and Horowicz, 1960;Lannergren, 1971] Horowicz, 1959]. As regards smooth muscle there is a linear relationship between the logarithm of the external concentration of potassium and the membrane potential of smooth muscle cells [Holman, 1957; Casteels and Kuriyama, 1966]. The purpose of th...

Isolation and contractile responses of single pregnant rat myometrial cells in short‐term primary culture and the effects of pharmacological and electrical stimuli

“…In single cells, the maximal contractile response was obtained with 135.6mM external K+ (present study) but with 60.6 mM external K+ in intact strips (Gabella, 1978;Mironneau et al, 1980). In intact strips, it has been suggested that the release of intramural noradrenaline by high K+ solution may explain the decrease in contraction observed in 135.6mM external K+ (Bengtsson, 1977).…”

Isolation and contractile responses of single pregnant rat myometrial cells in short‐term primary culture and the effects of pharmacological and electrical stimuli

“…In single cells, the maximal contractile response was obtained with 135.6mM external K+ (present study) but with 60.6 mM external K+ in intact strips (Gabella, 1978;Mironneau et al, 1980). In intact strips, it has been suggested that the release of intramural noradrenaline by high K+ solution may explain the decrease in contraction observed in 135.6mM external K+ (Bengtsson, 1977).…”

The Calcium Antagonistic Effects of Cyproheptadine on Contraction, Membrane Electrical Events and Calcium Influx in the Guinea‐pig Taenia Coli

“…L I-Effect of cyproheptadine on contractions evoked by exposure to and wash-out of isotonic KCI medium Exposure of taenia coli to isotonic KCl (solution 3, Table 1) evokes an initial phasic contraction that rapidly adapts to a lower tonically maintained level (Riemer et aL, 1974). As shown in Figure 4a, washout of the KCI solution evoked a further substantial increase in tension (repolarization contracture) followed by a marked increase in spontaneous activity (see also Gabella, 1978). The repolarization contracture (RC) is associated with a sustained high frequency discharge of action potentials during which the membrane potential is repolarizing (Holman, 1958).…”

Role of prostaglandins in lipopolysaccharide effects on K+‐induced contractions in rabbit small intestine

“…1999). Furthermore, adding K + solutions to isolated preparations of guinea‐pig gastrointestinal tract elicits a triphasic response; relaxation followed by contraction and a second relaxation (Gabella 1978).…”

“…However, K + solutions relax the duodenum and colon, and pre-contracted preparations with different agents (Toda et al 1992, Bö rjesson et al 1999). Furthermore, adding K + solutions to isolated preparations of guinea-pig gastrointestinal tract elicits a triphasic response; relaxation followed by contraction and a second relaxation (Gabella 1978).…”

Isolation and contractile responses of single pregnant rat myometrial cells in short‐term primary culture and the effects of pharmacological and electrical stimuli

“…In single cells, the maximal contractile response was obtained with 135.6mM external K+ (present study) but with 60.6 mM external K+ in intact strips (Gabella, 1978;Mironneau et al, 1980). In intact strips, it has been suggested that the release of intramural noradrenaline by high K+ solution may explain the decrease in contraction observed in 135.6mM external K+ (Bengtsson, 1977).…”

The Calcium Antagonistic Effects of Cyproheptadine on Contraction, Membrane Electrical Events and Calcium Influx in the Guinea‐pig Taenia Coli

“…L I-Effect of cyproheptadine on contractions evoked by exposure to and wash-out of isotonic KCI medium Exposure of taenia coli to isotonic KCl (solution 3, Table 1) evokes an initial phasic contraction that rapidly adapts to a lower tonically maintained level (Riemer et aL, 1974). As shown in Figure 4a, washout of the KCI solution evoked a further substantial increase in tension (repolarization contracture) followed by a marked increase in spontaneous activity (see also Gabella, 1978). The repolarization contracture (RC) is associated with a sustained high frequency discharge of action potentials during which the membrane potential is repolarizing (Holman, 1958).…”

Role of prostaglandins in lipopolysaccharide effects on K+‐induced contractions in rabbit small intestine

“…1999). Furthermore, adding K + solutions to isolated preparations of guinea‐pig gastrointestinal tract elicits a triphasic response; relaxation followed by contraction and a second relaxation (Gabella 1978).…”

“…However, K + solutions relax the duodenum and colon, and pre-contracted preparations with different agents (Toda et al 1992, Bö rjesson et al 1999). Furthermore, adding K + solutions to isolated preparations of guinea-pig gastrointestinal tract elicits a triphasic response; relaxation followed by contraction and a second relaxation (Gabella 1978).…”

Isolation and contractile responses of single pregnant rat myometrial cells in short‐term primary culture and the effects of pharmacological and electrical stimuli

“…In single cells, the maximal contractile response was obtained with 135.6mM external K+ (present study) but with 60.6 mM external K+ in intact strips (Gabella, 1978;Mironneau et al, 1980). In intact strips, it has been suggested that the release of intramural noradrenaline by high K+ solution may explain the decrease in contraction observed in 135.6mM external K+ (Bengtsson, 1977).…”

The Calcium Antagonistic Effects of Cyproheptadine on Contraction, Membrane Electrical Events and Calcium Influx in the Guinea‐pig Taenia Coli

“…L I-Effect of cyproheptadine on contractions evoked by exposure to and wash-out of isotonic KCI medium Exposure of taenia coli to isotonic KCl (solution 3, Table 1) evokes an initial phasic contraction that rapidly adapts to a lower tonically maintained level (Riemer et aL, 1974). As shown in Figure 4a, washout of the KCI solution evoked a further substantial increase in tension (repolarization contracture) followed by a marked increase in spontaneous activity (see also Gabella, 1978). The repolarization contracture (RC) is associated with a sustained high frequency discharge of action potentials during which the membrane potential is repolarizing (Holman, 1958).…”

Role of prostaglandins in lipopolysaccharide effects on K+‐induced contractions in rabbit small intestine

“…1999). Furthermore, adding K + solutions to isolated preparations of guinea‐pig gastrointestinal tract elicits a triphasic response; relaxation followed by contraction and a second relaxation (Gabella 1978).…”

“…However, K + solutions relax the duodenum and colon, and pre-contracted preparations with different agents (Toda et al 1992, Bö rjesson et al 1999). Furthermore, adding K + solutions to isolated preparations of guinea-pig gastrointestinal tract elicits a triphasic response; relaxation followed by contraction and a second relaxation (Gabella 1978).…”