Transient relaxation of rat mesenteric microvessels by ceramides

Abstract

1 We have investigated the vasodilating eects of D-erythro-C2-ceramide (C2-ceramide) in methoxamine-contracted rat mesenteric microvessels. 2 C2-ceramide (10 ± 100 mM) caused a concentration-dependent, slowly developing relaxation which reached maximum values after &10 min and partially abated thereafter. 3 Endothelium removal or inhibitors of guanylyl cyclase (3 mM ODQ), protein kinase A (10 mM H7, 1 mM H89) and various types of K + channels (10 mM BaCl 2 , 3 mM tetraethylammonium, 30 nM charybdotoxin, 30 nM iberiotoxin, 300 nM apamine, 10 mM glibenclamide) had only small if any inhibitory eects against C2-ceramide-induced vasodilation, but some of them attenuated vasodilation by sodium nitroprusside or isoprenaline. A combination of ODQ and charybdotoxin almost completely abolished C2-ceramide-induced vasodilation. 4 A second administration of C2-ceramide caused a detectable but weaker relaxation. L-threo-C2-ceramide (100 mM), which should not be a substrate to ceramide metabolism, had no biphasic time course. The ceramidase inhibitor (1S,2R)-D-erythro-2-(N-myristoylamino)-1-phenyl-1-propanol (100 mM) alone caused some vasodilation, indicating vasodilation by endogenous ceramides, and also hastened relaxation by exogenous C2-ceramide. The late-developing reversal of C2-ceramideinduced vasodilation was absent when a-adrenergic tone was removed by addition of 10 mM phentolamine. 5 We conclude that C2-ceramide relaxes rat resistance vessels in an endothelium-independent manner which is prevented only by combined inhibition of guanylyl cyclase and charybdotoxinsensitive K + channels. The vasodilation abates with time partly due to desensitization of the ceramide response and partly due to metabolism of C2-ceramide to an inactive metabolite.

Does Cyclic AMP Mediate Rat Urinary Bladder Relaxation by Isoproterenol?

“…Nevertheless, it must be stated that even combined inhibition accounted for only two thirds of the overall response against passive tension and did not at all explain relaxation against active tension. A similar synergistic effect was recently demonstrated for vascular smooth muscle relaxation by ceramide, which was only weakly sensitive to inhibition of guanylyl cyclase or BK Ca channels, whereas their combined inhibition abolished it (Czyborra et al, 2002).…”

“…Potassium channel opening, particularly as induced by BK Ca channel openers, mediates relaxation (Malysz et al, 2004). Some previous studies have linked ␤-adrenergic receptor stimulation to potassium channel opening (Czyborra et al, 2002;Horinouchi et al, 2003;Kathöfer et al, 2003). Specifically, it has been shown that ␤-adrenergic receptor stimulation in guinea pig urinary bladder activates BK Ca channels (Kobayashi et al, 2000).…”

“…To avoid desensitization, only a single relaxation curve was generated in each bladder strip. To avoid false negative findings, we have generally used high inhibitor concentrations corresponding to those used in previous studies (Czyborra et al, 2002).…”

Sphingosine Kinase–Dependent Activation of Endothelial Nitric Oxide Synthase by Angiotensin II

“…9 It can be hypothesized that this rheostat also plays a role in vascular contraction and relaxation because S1P, sphingosine, and ceramide are potentially counteracting, vasoactive compounds. 10,11 The molecular basis of ceramide effects has not been explored fully but is believed to involve stress-activated protein kinases, protein phosphatases such as protein phosphatases 1 and 2, guanylyl cyclase, and charybdotoxinsensitive K ϩ channels. 11,12 The molecular basis of S1P effects has been characterized in more detail.…”

“…10,11 The molecular basis of ceramide effects has not been explored fully but is believed to involve stress-activated protein kinases, protein phosphatases such as protein phosphatases 1 and 2, guanylyl cyclase, and charybdotoxinsensitive K ϩ channels. 11,12 The molecular basis of S1P effects has been characterized in more detail. S1P can act on specific G protein-coupled receptors, of which 5 subtypes have been identified thus far, termed S1P [1][2][3][4][5] .…”