Aim
During early post‐natal development, arterial contraction depends less on Ca2+‐signalling pathways but more on changes in Ca2+‐sensitivity compared to adult animals. Whether this difference is ...related to Rho‐kinase, one of the major players affecting Ca2+‐sensitivity, is unknown for intact vessels. Thus, we tested the hypothesis that Rho‐kinase critically contributes to the higher Ca2+‐sensitivity of contraction in intact arteries of 1‐week‐old rats.
Methods
We studied 1‐week‐old, 4‐ to 5‐week‐old and 10‐ to 12‐week‐old rats performing isometric myography, Ca2+‐fluorimetry and Western blotting using intact saphenous arteries and arterial pressure measurements under urethane anaesthesia.
Results
In 10‐ to 12‐week‐old rats, methoxamine (MX) produced vasoconstriction associated with an increase in Ca2+i and Ca2+‐sensitivity. In contrast, in 1‐week‐old rats these contractions were accompanied only by an increase in Ca2+‐sensitivity. All MX‐induced effects were reduced by the Rho‐kinase inhibitor Y‐27632; this reduction was complete only in 1‐week‐old rats. The Rho‐kinase specific site Thr855 on MYPT1 was increasingly phosphorylated by MX in vessels of 1‐week‐old, but not 10‐ to 12‐week‐old rats; this effect was also inhibited completely by Y‐27632. The Rho‐kinase inhibitor fasudil in a dose not affecting the pressor response to MX in 4‐ to 5‐week‐old rats reduced it considerably in 1‐week‐old rats.
Conclusion
Our results suggest that the higher Ca2+‐sensitivity of arterial contraction in 1‐week‐old compared to 10‐ to 12‐week‐old rats is due to a greater Rho‐kinase activity. Constitutively active Rho‐kinase contributes to MX‐induced contraction in 10‐ to 12‐week‐old rats. In 1‐week‐old rats, additional Rho‐kinase activation is involved. This remodelling of the Rho‐kinase pathway is associated with its increased contribution to adrenergic arterial pressure responses.
Aim
Protein kinases, activated by vasodilator substances, affect vascular function by regulating large conductance Ca2+‐activated K+ (KCa1.1) channels. Thus, the aim of the present investigation was ...to address the hypothesis that quercetin‐induced vasorelaxation is caused by a PKG‐mediated stimulation of KCa1.1 currents.
Methods
Single freshly isolated myocytes and endothelium‐denuded rings of the rat tail main artery were employed for electrophysiological and contractility measurements respectively.
Results
Quercetin relaxed vessels and increased KCa1.1 currents in a concentration‐dependent manner: both effects were antagonized by the specific KCa1.1 channel blocker iberiotoxin. Stimulation of KCa1.1 currents was fully reversible upon drug washout, markedly reduced by Rp‐8‐Br‐PET‐cGMPs, a PKG‐inhibitor, but not affected by catalase. Quercetin shifted by 34.3 mV the voltage dependence of KCa1.1 channel activation towards more negative membrane potentials without affecting its slope. Under conditions of tight functional coupling between sarcoplasmic reticulum Ca2+ release sites and KCa1.1 channels, quercetin decreased both the frequency and the amplitude of KCa1.1 transient currents in a ryanodine‐like manner.
Conclusion
The natural flavonoid quercetin relaxes the rat tail main artery partly via a PKG‐mediated stimulation of smooth muscle KCa1.1 channels.
During early post-natal development, arterial contraction depends less on Ca
-signalling pathways but more on changes in Ca
-sensitivity compared to adult animals. Whether this difference is related ...to Rho-kinase, one of the major players affecting Ca
-sensitivity, is unknown for intact vessels. Thus, we tested the hypothesis that Rho-kinase critically contributes to the higher Ca
-sensitivity of contraction in intact arteries of 1-week-old rats.
We studied 1-week-old, 4- to 5-week-old and 10- to 12-week-old rats performing isometric myography, Ca
-fluorimetry and Western blotting using intact saphenous arteries and arterial pressure measurements under urethane anaesthesia.
In 10- to 12-week-old rats, methoxamine (MX) produced vasoconstriction associated with an increase in Ca
and Ca
-sensitivity. In contrast, in 1-week-old rats these contractions were accompanied only by an increase in Ca
-sensitivity. All MX-induced effects were reduced by the Rho-kinase inhibitor Y-27632; this reduction was complete only in 1-week-old rats. The Rho-kinase specific site Thr
on MYPT1 was increasingly phosphorylated by MX in vessels of 1-week-old, but not 10- to 12-week-old rats; this effect was also inhibited completely by Y-27632. The Rho-kinase inhibitor fasudil in a dose not affecting the pressor response to MX in 4- to 5-week-old rats reduced it considerably in 1-week-old rats.
Our results suggest that the higher Ca
-sensitivity of arterial contraction in 1-week-old compared to 10- to 12-week-old rats is due to a greater Rho-kinase activity. Constitutively active Rho-kinase contributes to MX-induced contraction in 10- to 12-week-old rats. In 1-week-old rats, additional Rho-kinase activation is involved. This remodelling of the Rho-kinase pathway is associated with its increased contribution to adrenergic arterial pressure responses.
Aerobic exercise training is associated with adaptive changes in skeletal muscles and their vascular bed; such changes in individual muscles may vary depending on their characteristics and ...recruitment. This study was aimed at comparing the effects of eight-week treadmill training on the locomotor and respiratory muscles in rats. The training course increased the aerobic performance in rats, which was evidenced by an increase in maximum O
2
consumption and a decrease in the blood lactate concentration in ramp test. The succinate dehydrogenase activity was increased in the red portion of the gastrocnemius muscle, but not in the diaphragm of trained rats. Arterial segments were isolated from feed arteries and studied by wire myography. The relaxation in response to acetylcholine in gastrocnemius arteries in trained animals was higher as compared with controls (due to higher NO production), while contractile responses to noradrenaline (in the presence of propranolol) were not changed. On the contrary, the endothelial function of diaphragm arteries was not affected by training, but contractile responses to activation of α-adrenoceptors were markedly increased. Thus, aerobic training may increase the blood supply rate to both locomotor and respiratory muscles, but the underlying regulatory mechanisms are different. The results obtained allow us to reveal the physiological mechanisms that determine the physical performance of the body under conditions of compromised functioning of the respiratory system.
Abstract
Aim
Protein kinases, activated by vasodilator substances, affect vascular function by regulating large conductance
Ca
2+
‐activated
K
+
(
K
Ca
1.1) channels. Thus, the aim of the present ...investigation was to address the hypothesis that quercetin‐induced vasorelaxation is caused by a
PKG
‐mediated stimulation of
K
Ca
1.1 currents.
Methods
Single freshly isolated myocytes and endothelium‐denuded rings of the rat tail main artery were employed for electrophysiological and contractility measurements respectively.
Results
Quercetin relaxed vessels and increased
K
Ca
1.1 currents in a concentration‐dependent manner: both effects were antagonized by the specific
K
Ca
1.1 channel blocker iberiotoxin. Stimulation of
K
Ca
1.1 currents was fully reversible upon drug washout, markedly reduced by Rp‐8‐Br‐
PET
‐
cGMP
s, a
PKG
‐inhibitor, but not affected by catalase. Quercetin shifted by 34.3 mV the voltage dependence of
K
Ca
1.1 channel activation towards more negative membrane potentials without affecting its slope. Under conditions of tight functional coupling between sarcoplasmic reticulum
Ca
2+
release sites and
K
Ca
1.1 channels, quercetin decreased both the frequency and the amplitude of
K
Ca
1.1 transient currents in a ryanodine‐like manner.
Conclusion
The natural flavonoid quercetin relaxes the rat tail main artery partly
via
a
PKG
‐mediated stimulation of smooth muscle
K
C
a
1.1 channels.
The age-related dynamics of the activity of signalling pathways coupled to alpha1-adrenergic receptors and their dependence on the sympathetic innervation of arterial smooth muscle have been studied. ...The effects of the protein kinase C inhibitor (GF109203X, 10(-6) M) and the Rho-kinase inhibitor (Y27632, 10(-5) M) on the isometric contraction of the rat saphenous artery, induced by the alpha1-adrenoceptor agonist methoxamine, were examined. It was shown that the sensitivity to methoxamine of arteries from 2-week-old rats that are partially innervated was reduced as compared to adults, but the effects of both inhibitors were more prominent. The denervation induced by the excision of sympathetic ganglia increased the arterial sensitivity to methoxamine but was not accompanied by changes in sensitivity to the inhibitors. Therefore, the postnatal development of the arterial smooth muscle is characterized by a decrease in the contribution of protein kinase C and Rho-kinase to the regulation of contraction; however, these changes do not correlate with changes in the sensitivity of arteries to methoxamine and development of sympathetic innervation.
The characteristics of feeding arteries of diaphragm and medial gastrocnemius (with a diameter of 200-250 micron) were studied. The registration of the mechanical activity of ring preparations under ...isometric conditions revealed that diaphragm arteries, like arteries of other muscles with a high content of slow muscle fibers, are highly sensitive to adrenoceptor agonists and acetylcholine. The differences in endothelium-dependent relaxation between diaphragm and gastrocnemius arteries are preserved in the presence of L-NAME and diclofenac. Responses to serotonin in diaphragm and gastrocnemius arteries are similar. At the same time, the high density of innervation is characteristic of diaphragm artery only, while in other slow muscles it is low. The density of adrenergic fibers plexus in the diaphragm artery is much higher than in the gastrocnemius artery. The results suggest that the properties of small arteries of diaphragm are determined not only by the oxidative capacity of diaphragm muscle fibers but also by the belonging of the diaphragm to respiratory musculature.
Changes in contractile activity of saphenous artery in normotensive rats and in rats with regional hypotension have been investigated. The abdominal aorta was partially occluded in Wistar rats ...distally to the renal arteries. Four weeks later, a 5-7-mm segment of the femoral nerve in one hindlimb was resected to denervate the saphenous artery. After two weeks, the isometric contraction of innervated and denervated saphenous artery segments was studied. In normotensive rats, the denervation augmented vessel sensitivity to noradrenaline, phenylephrine, serotonin, and KCl (in the presence of phentolamine). Chronic hypotension also augmented vessel sensitivity to constrictor agonists, whereas denervation did not result in further increase of sensitivity. In glyoxilic acid-stained preparations obtained from hypotensive rats, a reduced intensity of fluorescence of adrenergic fibers was observed. It was assumed that the higher sensitivity of vascular smooth muscle in hypotensive rats is due to functional disturbances of sympathetic innervation.
Protein kinases, activated by vasodilator substances, affect vascular function by regulating large conductance Ca(2+) -activated K(+) (KCa 1.1) channels. Thus, the aim of the present investigation ...was to address the hypothesis that quercetin-induced vasorelaxation is caused by a PKG-mediated stimulation of KCa 1.1 currents.
Single freshly isolated myocytes and endothelium-denuded rings of the rat tail main artery were employed for electrophysiological and contractility measurements respectively.
Quercetin relaxed vessels and increased KCa 1.1 currents in a concentration-dependent manner: both effects were antagonized by the specific KCa 1.1 channel blocker iberiotoxin. Stimulation of KCa 1.1 currents was fully reversible upon drug washout, markedly reduced by Rp-8-Br-PET-cGMPs, a PKG-inhibitor, but not affected by catalase. Quercetin shifted by 34.3 mV the voltage dependence of KCa 1.1 channel activation towards more negative membrane potentials without affecting its slope. Under conditions of tight functional coupling between sarcoplasmic reticulum Ca(2+) release sites and KCa 1.1 channels, quercetin decreased both the frequency and the amplitude of KCa 1.1 transient currents in a ryanodine-like manner.
The natural flavonoid quercetin relaxes the rat tail main artery partly via a PKG-mediated stimulation of smooth muscle KC a 1.1 channels.
Addition of N-acetylcysteine induced relaxation of the coronary and basilar arteries thus indicating some basilar NO-stores in these vessels. The maximum capacity of the NO-stores was similar in the ...coronary and the basilar arteries. Following adaptation to hypoxia, however, the depot was much greater in the coronary artery wall. This seems to be connected with different degree of participation of the NO-dependent vasodiatation in implementation of the adaptive response to hypoxia in coronary and cerebral vascular systems.
