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Effects of pH on vascular tone in rabbit basilar arteries.

Kim YC, Lee SJ, Kim KW - J. Korean Med. Sci. (2004)

Bottom Line: Since high K+- and histamine-induced tonic contractions were affected by nicardipine and pHo, the effect of pHo on voltage-dependent L-type Ca2+ channel (VDCCL) was studied.VDCCL was modulated by pHo: the peak value of Ca2+ channel current (IBa) at a holding of 0 mV decreased in [acidosis]o by 41+/-8.8%, whereas that increased in [alkalosis]o by 35+/-2.1% (n=3).These results suggested that the external pH regulates vascular tone partly via the modulation of VDCC in rabbit basilar arteries.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Chungbuk National University College of Medicine, Cheongju, Korea.

ABSTRACT
Effects of pH on vascular tone and L-type Ca2+ channels were investigated using Mulvany myograph and voltage-clamp technique in rabbit basilar arteries. In rabbit basilar arteries, high K+ produced tonic contractions by 11+/-0.6 mN (mean+/-S.E.,n=19). When extracellular pH (pHo) was changed from control 7.4 to 7.9 ([alkalosis]o), K+-induced contraction was increased to 128+/-2.1% of the control (n=13). However, K+-induced contraction was decreased to 73+/-1.3% of the control at pHo 6.8 ([acidosis] o, n=4). Histamine (10 microM) also produced tonic contraction by 11+/-0.6 mN (n=17), which was blocked by post-application of nicardipine (1 microM). [alkalosis]o and [acidosis]o increased or decreased histamine-induced contraction to 134+/-5.7% and 27+/-7.6% of the control (n=4, 6). Since high K+- and histamine-induced tonic contractions were affected by nicardipine and pHo, the effect of pHo on voltage-dependent L-type Ca2+ channel (VDCCL) was studied. VDCCL was modulated by pHo: the peak value of Ca2+ channel current (IBa) at a holding of 0 mV decreased in [acidosis]o by 41+/-8.8%, whereas that increased in [alkalosis]o by 35+/-2.1% (n=3). These results suggested that the external pH regulates vascular tone partly via the modulation of VDCC in rabbit basilar arteries.

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Effects of alteration of pHo on the histamine-induced contraction in basilar arteries of rabbits. 10 µM of histamine produced tonic contractions in rabbit basilar artery. (A, B) Histamine-induced contraction was decreased or increased by pHo 6.8 or pHo 7.9 in a reversible manner. (C) Bar graphs show mean relative histamine-induced contraction by alteration of pHo. Asterisks indicate the data which were considered to be significantly different from control data (**p<0.01).
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Figure 4: Effects of alteration of pHo on the histamine-induced contraction in basilar arteries of rabbits. 10 µM of histamine produced tonic contractions in rabbit basilar artery. (A, B) Histamine-induced contraction was decreased or increased by pHo 6.8 or pHo 7.9 in a reversible manner. (C) Bar graphs show mean relative histamine-induced contraction by alteration of pHo. Asterisks indicate the data which were considered to be significantly different from control data (**p<0.01).

Mentions: As shown in Fig. 3A, histamine (1-20 µM) produced a contraction in a concentration-dependent manner, and maximal contraction was observed approximately at 10 µM of histamine (22). In a few cases, oscillatory small phasic contractions were observed after the application of histamine (Fig. 3B). Histamine (10 µM) developed a tonic contraction with the amplitude of 11±0.6 mN (n=17, Fig. 4), which was blocked by post-application of nicardipine (1 µM), known as a blocker of Ca2+ channel (L-type) (Fig. 3C). From the 14 tested tissues, histamine-induced sustained contractions were suppressed by nicardipine (1 µM) to 21±7.3% of the control (Fig. 5B). These results suggest that Ca2+ influx through Ca2+ channel (L-type) might be important in the histamine-induced tonic contraction. Histamine-induced contractions were enhanced or suppressed under the condition of [alkalosis]o or [acidosis]o to 134±5.7% and to 27±7.6% of the control in a reversible manner (Fig. 4; n=5, 6, p<0.01), respectively.


Effects of pH on vascular tone in rabbit basilar arteries.

Kim YC, Lee SJ, Kim KW - J. Korean Med. Sci. (2004)

Effects of alteration of pHo on the histamine-induced contraction in basilar arteries of rabbits. 10 µM of histamine produced tonic contractions in rabbit basilar artery. (A, B) Histamine-induced contraction was decreased or increased by pHo 6.8 or pHo 7.9 in a reversible manner. (C) Bar graphs show mean relative histamine-induced contraction by alteration of pHo. Asterisks indicate the data which were considered to be significantly different from control data (**p<0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2822262&req=5

Figure 4: Effects of alteration of pHo on the histamine-induced contraction in basilar arteries of rabbits. 10 µM of histamine produced tonic contractions in rabbit basilar artery. (A, B) Histamine-induced contraction was decreased or increased by pHo 6.8 or pHo 7.9 in a reversible manner. (C) Bar graphs show mean relative histamine-induced contraction by alteration of pHo. Asterisks indicate the data which were considered to be significantly different from control data (**p<0.01).
Mentions: As shown in Fig. 3A, histamine (1-20 µM) produced a contraction in a concentration-dependent manner, and maximal contraction was observed approximately at 10 µM of histamine (22). In a few cases, oscillatory small phasic contractions were observed after the application of histamine (Fig. 3B). Histamine (10 µM) developed a tonic contraction with the amplitude of 11±0.6 mN (n=17, Fig. 4), which was blocked by post-application of nicardipine (1 µM), known as a blocker of Ca2+ channel (L-type) (Fig. 3C). From the 14 tested tissues, histamine-induced sustained contractions were suppressed by nicardipine (1 µM) to 21±7.3% of the control (Fig. 5B). These results suggest that Ca2+ influx through Ca2+ channel (L-type) might be important in the histamine-induced tonic contraction. Histamine-induced contractions were enhanced or suppressed under the condition of [alkalosis]o or [acidosis]o to 134±5.7% and to 27±7.6% of the control in a reversible manner (Fig. 4; n=5, 6, p<0.01), respectively.

Bottom Line: Since high K+- and histamine-induced tonic contractions were affected by nicardipine and pHo, the effect of pHo on voltage-dependent L-type Ca2+ channel (VDCCL) was studied.VDCCL was modulated by pHo: the peak value of Ca2+ channel current (IBa) at a holding of 0 mV decreased in [acidosis]o by 41+/-8.8%, whereas that increased in [alkalosis]o by 35+/-2.1% (n=3).These results suggested that the external pH regulates vascular tone partly via the modulation of VDCC in rabbit basilar arteries.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Chungbuk National University College of Medicine, Cheongju, Korea.

ABSTRACT
Effects of pH on vascular tone and L-type Ca2+ channels were investigated using Mulvany myograph and voltage-clamp technique in rabbit basilar arteries. In rabbit basilar arteries, high K+ produced tonic contractions by 11+/-0.6 mN (mean+/-S.E.,n=19). When extracellular pH (pHo) was changed from control 7.4 to 7.9 ([alkalosis]o), K+-induced contraction was increased to 128+/-2.1% of the control (n=13). However, K+-induced contraction was decreased to 73+/-1.3% of the control at pHo 6.8 ([acidosis] o, n=4). Histamine (10 microM) also produced tonic contraction by 11+/-0.6 mN (n=17), which was blocked by post-application of nicardipine (1 microM). [alkalosis]o and [acidosis]o increased or decreased histamine-induced contraction to 134+/-5.7% and 27+/-7.6% of the control (n=4, 6). Since high K+- and histamine-induced tonic contractions were affected by nicardipine and pHo, the effect of pHo on voltage-dependent L-type Ca2+ channel (VDCCL) was studied. VDCCL was modulated by pHo: the peak value of Ca2+ channel current (IBa) at a holding of 0 mV decreased in [acidosis]o by 41+/-8.8%, whereas that increased in [alkalosis]o by 35+/-2.1% (n=3). These results suggested that the external pH regulates vascular tone partly via the modulation of VDCC in rabbit basilar arteries.

Show MeSH
Related in: MedlinePlus