Role of Endothelium-derived Hyperpolarizing Factor in Phenylephrine-induced Oscillatory Vasomotion in Rat Small Mesenteric Artery

Abstract

Endothelially-derived NO is an important modulator of sustained agonist-induced vasoconstriction. NO, as well as endothelially-derived cyclooxygenase products and EDHF, also contribute significantly to phenylephrine-induced oscillatory vasomotion.

Essential role of EDHF in the initiation and maintenance of adrenergic vasomotion in rat mesenteric arteries

“…Vasomotion still occurred in all arteries in response to 1.0 M PE (n ϭ 3, control: 0.059 Ϯ 0.008; LNNA ϩ ODQ: 0.031 Ϯ 0.008; Table 1). The results with L-NAME, L-NNA, and ODQ agree well with the results of Sell and colleagues (43) and Okazaki and colleagues (30). NO and cGMP play modulatory roles in the generation of adrenergic vasomotion in rat mesenteric arteries.…”

“…Part of the relaxation, in response to endothelial stimulation with acetylcholine (ACh) or bradykinin (BK), is mediated via NO in mesenteric arteries (34), but a significant component is attributed to apamin (Apa)-and charybdotoxin (ChTX)-sensitive EDHF (5,33). The possibility that an endothelial factor other than NO is responsible for the generation of vasomotion has been examined recently (30), and the results indicated that EDHF is also involved in vasomotion. Nevertheless, the study did not indicate whether inhibition of Ca 2ϩ -activated K ϩ (K Ca ) channels alone, with Apa and ChTX, without the simultaneous inhibition of NO synthase and cyclooxygenase, was sufficient to abolish vasomotion.…”

Effects of K+ Channel Modulators on Oscillatory Contractions in Sinoaortic Denervated Rat Aortas

“…BK Ca is thought to play an important physiological role in the repolarization phase of the action potential. In earlier studies, it has been demonstrated that BK Ca plays an important role in controling oscillatory contractions in some smooth muscle preparations, such as the rat basilar artery, 11) rat mesenteric artery 10,12) and rabbit ear artery. 7) In our hands, the inhibition of BK Ca with iberiotoxin altered the oscillatory contractions, increasing their frequency and decreasing their amplitude.…”

“…[7][8][9][10] The effect of oscillatory contractions on vascular beds is currently controversial, so its physiological significance is yet to be correctly defined.…”

“…Furthermore, the participation of the different types of K ϩ channels can vary depending on the initial oscillatory incentive and on the vascular beds being studied. For example, Ca 2ϩ -activated K ϩ channels (K Ca ) play an important role in the maintenance of the oscillations and their blockade inhibits oscillatory contractions in the rat basilar artery, 11) rat mesenteric artery, 10,12) and rabbit ear artery. 7) In contrast, the K Ca blockade has no effects on the oscillations in the rat tail arteries, 13) while it is responsible for amplifying the oscillations in the guinea-pig urinary bladder.…”