Role of nitric oxide in β₃-adrenoceptor activation on basal tone of internal anal sphincter

Abstract

Banwait, Kuldip S. and Satish Rattan. Role of nitric oxide in ␤3-adrenoceptor activation on basal tone of internal anal sphincter. Am J Physiol Gastrointest Liver Physiol 285: G547-G555, 2003. First published May 7, 2003 10.1152/ ajpgi.00545.2002.-Effects of activation of ␤3-adrenoceptor (␤3-AR) have not been determined in the spontaneously tonic smooth muscle of the internal anal sphincter (IAS). The effects of disodium (R,R)-5-[2-[2-3-chlorophenyl)-2-hydroxyethyl]-amino]propyl]-1,3-benzodioxole-2,2-dicarboxylate (CL 316243), a selective ␤3-AR agonist, on the basal smooth muscle tone and direct release of nitric oxide (NO) by circular smooth muscle strips of the opossum IAS were determined. We also examined the presence of endothelial nitric oxide synthase (eNOS) protein by Western blot studies. CL 316243 produced a concentration-dependent relaxation of the smooth muscle that remained unmodified by different neurohumoral antagonists. The smooth muscle relaxation by CL 316243 was selectively antagonized by L 748337, a ␤3-AR antagonist. Such relaxation was several times longer than by isoproterenol. The effect of CL 316243 was significantly attenuated by a nonselective NOS inhibitor N -nitro-L-arginine (L-NNA) and by putative inhibitor of eNOS L-N 5 -(1-iminoethyl)-ornithine dihydrochloride (L-NIO). Inhibitors of iNOS [N-(3-aminomethyl)benzyl acetamide 2HCl] and nNOS {1-[2-(trifluoromethylphenyl)imidazole]} had no effect on this relaxation. Relaxation of the IAS smooth muscle induced by CL 316243 was accompanied by an increased release of NO; this was attenuated by L-NNA and L-NIO. In addition, Western blot studies revealed the presence of eNOS in the circular smooth muscle of the IAS. These data demonstrate potent and protracted IAS smooth muscle relaxation by ␤3-AR activation, which is partly transduced via NOS, possibly smooth muscle eNOS. Multiple signal-transduction pathways including NOS activation may explain the characteristic IAS relaxation by ␤3-AR activation. The studies may have therapeutic implications in anorectal motility disorders.internal anal sphincter smooth muscle; nitric oxide synthase; nitric oxide synthase inhibitors; nonadrenergic noncholinergic relaxation; Hirschsprung's disease THE ␤ 3 -ADRENOCEPTOR (␤ 3 -AR), discovered in 1989 (11), has been identified in different regions of gastrointestinal (GI) tract, ureter, urinary bladder, uterus, prostate, white fat, and in the cardiovascular system in humans (1-3, 8, 12, 28, 31, 36). We have shown (10) that the characteristics of relaxation of the lower esophageal sphincter (LES) smooth muscle in response to activation of the ␤ 3 -AR are very much different from relaxation in response to activation of the ␤ 1 -or ␤ 2 -AR: ␤ 3 -AR activation by the selective agonist is characteristically antagonized by the ␤ 3 -selective antagonist.It is well known that stimulation of ␤-ARs (␤ 1 , ␤ 2 , or ␤ 3 ) causes release of G s ␣, which then activates adenylate cyclase to produce cAMP (34, 41). Elevated levels of cAMP produce relaxation of smooth muscle v...

Ischemic Preconditioning Attenuates Postischemic Leukocyte - Endothelial Cell Interactions Role of Nitric Oxide and Protein Kinase C

“…41 It has also been suggested that I/R upregulates iNOS expression, and that inhibition of iNOS improves contractile function and blood flow. 42 However, other studies have shown that induction of iNOS, by prior administration of monophosphoryl lipid A, conferred myocardial protection against I/R injury.…”

Role of Adenylate and Guanylate Cyclases in β1-, β2-, and β3-Adrenoceptor-Mediated Relaxation of Internal Anal Sphincter Smooth Muscle

“…The procedure to describe details of tissue preparation and isometric tension recording in the IAS smooth muscle has been published in a number of our earlier publications (Moummi and Rattan, 1988;Banwait and Rattan, 2003;Rathi et al, 2003;Sarma et al, 2003).…”

“…This hypothesis is further corroborated by the actual determinations of cGMP levels. Biochemical pathway for ␤ 3 -AR activation-mediated IAS smooth muscle relaxation is similar to that by neuronal nitric-oxide synthase and endothelial nitric-oxide synthase activation in the IAS (Rattan and Chakder, 1992;Chakder and Rattan, 1993;Banwait and Rattan, 2003). Data with ␤ 3 -AR activation in the IAS in view of its prolonged, selective, systemic effects-free effect (DiMarino et al, 2002;Banwait and Rattan, 2003) combined with the utilization of biochemical pathway common to nonadrenergic noncholinergic nerve stimulation are important from the standpoint of anorectal and other gastrointestinal motility disorders.…”

Diabetes Mellitus and Anal Sphincter Pressures: An Experimental Model in Rats

“…They concluded that nitric oxide was an important substance involved in the relaxation of the smooth musculature of the anal canal. 7,9,10,24 To investigate the role of nitric oxide in sphincter hypotony of streptozotocin-induced diabetic rats, we used an antagonist of nitric oxide synthase: L-NAME. 25 We used L-NAME in the form of an enema in diabetic rats with sphincter hypotony 60 days after induction.…”

“…This suggestion is based on the following points: 1) direct inhibitory action of nitric oxide on the musculature, and 2) blockade of the inhibitory action of nonadrenergic and noncholinergic neurons through the use of inhibitors of the nitric oxide synthase (NOS). [8][9][10] The internal anal sphincter is a smooth muscle known to be under inhibitory control of nitric oxide. The use of Wistar rats as a model for experimental study is widely accepted, and its use for the study of diabetes and its complications is well documented.…”