Agonist-induced periodic vasomotion in rat isolated pulmonary artery

Abstract

Vasomotion is linked to the rapid oscillations of intracellular calcium levels. In rat pulmonary artery, this activity can manifest as a slow periodic on-off pattern, the timing of which depends on the type and intensity of pharmacological stimuli employed. In this study, we have sought to characterize a slow-wave vasomotor activity pattern induced in isolated arterial ring preparations by simultaneous exposure to the α(1) -adrenoceptor agonist phenylephrine (1-10 nm) and the L channel agonist S(-)-Bay K 8644 (3-20 nm). Treated tissues responded with a stable on-off pattern of vasomotion persisting for >5 h at 5-6 cycles/h. In intact rings, this response was suppressed by methacholine and restored or enhanced by N(ω) -nitro-l-arginine methyl ester. Analogous inhibitory effects were obtained with high Mg(2+) , 8-Br-cGMP (but not 8-Br-cAMP), riluzole, ryanodine, chelerythrine, and fasudil. Pinacidil (30 nm) increased off-cycle length without change in slow-wave amplitude. Conversely, tetraethylammonium (1.0-3.0 mm) augmented the latter without affecting periodicity. Carbenoxolone (10 μm) abolished slow-wave activity, while raising basal tone and inducing random phasic activity. In endothelium-denuded rings, the threshold of agonist-induced slow-wave vasomotion was lowered and a similar inhibitory effect obtained with carbenoxolone. In conclusion, the slow-wave pattern of vasomotion described here is (i) subject to inhibitory modulation by endothelial NO and an array of voltage-gated and leak K conductances yet to be fully characterized; (ii) dependent on Ca(2+) from both extracellular and sarcoendoplasmatic sources; (iii) controlled by kinase (Rho and PKC)-mediated regulation of myosin light chain phosphatase; and (iv) synchronized via intermyocyte gap junctions.

Synchronization in the Heart Rate and the Vasomotion in Rat Aorta: Effect of Arsenic Trioxide

“…However, the results showed that in rats chronically exposed to arsenic, the QTc interval decreased by 10 %, suggesting that there might be other factors responsible for the decrease in heart rate in the same rats. Reports in the literature state that the R t interval is involved in the repolarization of the vascular smooth muscle cell and the frequency of vasomotion that exists [28]. Therefore, the decrease in the frequency of vasomotion in the artery could be accounted for as a block in potassium channels (i.e., Kir channels) [29].…”

Potassium-induced intermittent vasomotion in rat isolated pulmonary artery

“…In preliminary work we have been able to observe, by means of in vitro pressure recordings from a preparation consisting of the trunk and two main pulmonary arteries, the intermittent vasomotor activity pattern described here in ring preparations. As we recently reported this same pattern of vasomotion can be induced by application of agonist (Burke et al, 2010).…”

Role of Calcium-Activated Potassium Channels in the Genesis of 3,4-Diaminopyridine-Induced Periodic Contractions in Isolated Canine Coronary Artery Smooth Muscles

“…Periodic or rhythmic contractions are produced in the human vas deferens by Bay K8644,which is blocked by nifedipine and verapamil (Amobi et al, 2010). Burke et al (2010) also observed PCs of the rat pulmonary artery induced by phenylephrine and Bay K8644. In the present study, however, PCs was not induced by Bay K8644, whereas they were suppressed by phenylephrine.…”