Enhancement by L-methionine on the contractile response of uterine segments to acetylcholine and high KCl is mainly due to enhancement of Ca uptake.

Ichida, Seiji; Yoshioka, Kazuo; Ariyoshi, Shunji; Fujisue, Takashi

doi:10.1254/jjp.52.154

Cited by 3 publications

(3 citation statements)

References 12 publications

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“…1, A, B, C, D, E and F), as observed previously by others in rat cardiac cells and NG 108-15 cells (14,15). We also examined whether they did affect the 45Ca uptake by ACh which was used to stimualte 45 Ca uptake in rat uterine segments as reported previously (13,16). They do not appreciably increase ACh (10-6 M)-stimulated 45Ca uptake (Fig.…”

Section: Discussionsupporting

confidence: 67%

Effects of Calcium Channel Agonists (BAYK8644, CGP28392 and YC-170) on 45Ca Uptake by Rat Uterine Segments.

et al. 1991

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ABSTRACT-The characteristics of the stimulating effects of the calcium channel agonists BAY K 8644, CGP28392 and YC-170 on 45Ca uptake by rat uterine segments were investigated. BAY K 8644, CGP28392 and YC-170 caused about 150, 100 and 150% increase, respectively in the 45Ca uptake induced by 20 mM KC1. The ED50 values of BAY K 8644, CGP28392 and YC-170 were 1.8 X 109, 2.5 X 10-8 and 9.8 X 109 M, respectively. These agonists had little effect on the 45Ca uptake induced by 10-6 M acetylcholine. They also did not affect the basal 45Ca uptake. Their enhancing effects were blocked by the Ca channel antagonist nitrendipine. We conclude that rat uterine segments have voltage-sensitive Ca channels that are stimulated by Ca channel agonists (BAY K 8644, CGP28392 and YC-170) under depolarizing conditions and that the characteristics of the stimulating effects of CGP28392 and YC-170 on 45Ca uptake by rat uterine segments are qualitatively the same as those of BAY K 8644.Ca channels are important in excitation secretion coupling, because increase in the cytoplasmic concentration of free Ca plays a key role in the regulation of Ca-dependent enzyme activity and hormone release (1).Some 1,4-dihydropyridine (DHP) deriva tives are known to block the flow of Ca 2+ through voltage-sensitive Ca channels. Con versely, DHP derivatives such as BAY K 8644 (BAY), CGP28392 (CGP) and YC-170 (YC) (2-6) have recently been found to act as Ca channel agonists and increase the Ca current in various excitable cells (7-11). These ago nists and antagonists have been utilized in studying how voltage-sensitive Ca channels are physiologically (normally) regulated (7).We previously reported the characteristics of Ca influxes through voltage and receptor operated Ca channels in rat uterine muscle (12). In this work, we examined the character isics of the stimulating effects of BAY, CGP and YC on 45Ca uptake by rat uterine seg ments to elucidate how voltage-sensitive Ca channels in rat uterine muscle are physiologi cally regulated. A preliminary report of this work has appeared in abstract form (13).

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Section: Discussionsupporting

confidence: 67%

Effects of Calcium Channel Agonists (BAYK8644, CGP28392 and YC-170) on 45Ca Uptake by Rat Uterine Segments.

et al. 1991

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“…It was previously shown that 3-deazaadenosine plus homocysteine thiolactone dose dependently inhibited acetylcholine (Ach) and high KClinduced contractions in rat uterine segments, and this effect was attenuated by L-methionine (11). In contrast to our study, no effect of homocysteine thiolactone on the contractility of rat myometrium was found.…”

Section: Discussioncontrasting

confidence: 99%

Homocysteine-induced enhancement of spontaneous contractions of myometrium isolated from pregnant women

Ayar¹,

Çelik²,

Özçelik³

et al. 2003

Acta Obstet Gynecol Scand

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Background. Although many associations have been demonstrated between hyperhomocysteinemia and pregnancy complications, such as spontaneous abortion, preterm labor, preeclampsia and low birthweight, it is still not clear whether hyperhomocysteinemia is the cause or the consequence of these pregnancy complications. The aim of this study was to investigate the effects of homocysteine on the spontaneous contractility of isolated pregnant human myometrium. Methods. Myometrium samples obtained from women undergoing elective caesarean section were suspended in a jacketed organ bath containing Krebs' solution at 37 C (pH 7.4), continuously gassed with 95% O 2 and 5% CO 2 . After manifestation of spontaneous contractions under 2 g of resting tension, homocysteine was applied to the organ bath, and amplitude and frequency of contractions were evaluated at 20-min intervals. Statistical analysis of amplitude and frequency of the contractions was performed using the Kruskal-Wallis analysis of variance test. Results. Application of 0.1 mM homocysteine had no significant effect on either frequency (4.63 AE 0.42 vs. 4.01 AE 0.53 for the control period; p > 0.05) or amplitude (3.20 AE 0.07 g vs. 3.15 AE 0.07 g; p > 0.05) of spontaneous contractions, while 1 and 2 mM homocysteine significantly increased the frequency (8.54 AE 0.62 vs. 3.9 AE 0.44, p < 0.02, and 12.32 AE 0.72 vs. 3.96 AE 0.51, p < 0.001, respectively) of spontaneous contractions but caused only a modest change in amplitude (2.92 AE 0.04 g vs. 2.87 AE 0.05 g, p > 0.05, and 3.02 AE 0.06 g vs. 2.93 AE 0.05 g, p > 0.05, respectively). Conclusion. Results from this study indicate for the first time that homocysteine causes enhancement of spontaneous contractions of myometrium derived from pregnant women.

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“…It was previously shown that 3‐deazaadenosine plus homocysteine thiolactone dose dependently inhibited acetylcholine (Ach) and high KCl‐induced contractions in rat uterine segments, and this effect was attenuated by l ‐methionine (11). In contrast to our study, no effect of homocysteine thiolactone on the contractility of rat myometrium was found.…”

Section: Discussionmentioning

confidence: 99%

Homocysteine‐induced enhancement of spontaneous contractions of myometrium isolated from pregnant women

Ayar¹,

Çelik²,

Özçelik

et al. 2003

Acta Obstet Gynecol Scand

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show abstract

Enhancement by L-methionine on the contractile response of uterine segments to acetylcholine and high KCl is mainly due to enhancement of Ca uptake.

Cited by 3 publications

References 12 publications

Effects of Calcium Channel Agonists (BAYK8644, CGP28392 and YC-170) on 45Ca Uptake by Rat Uterine Segments.

Effects of Calcium Channel Agonists (BAYK8644, CGP28392 and YC-170) on 45Ca Uptake by Rat Uterine Segments.

Homocysteine-induced enhancement of spontaneous contractions of myometrium isolated from pregnant women

Homocysteine‐induced enhancement of spontaneous contractions of myometrium isolated from pregnant women

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