Effects of inhibition of the l‐arginine/nitric oxide pathway in the rat lower urinary tract in vivo and in vitro

Abstract

1 The present study was performed to investigate how blockade of the L-arginine/nitric oxide (NO) pathway influences the function of the lower urinary tract in vivo, as studied by cystometry in conscious rats and in vitro, in isolated muscle preparations from the rat detrusor and urethra. 2 L-N0-nitro arginine methyl ester (L-NAME), 10 and 20 mg kg-, administered intra-arterially, decreased micturition volume and bladder capacity, and increased spontaneous bladder contractions. D-NAME (20mgkg-') had no effect. No changes in the urodynamic parameters were recorded if L-NAME (20mgkg-') was administered in combination with L-arginine (200mgkg-'). 3 Cystometries performed after intra-arterial administration of sodium nitroprusside (SNP) (3mg kg-') and 3-morpholino-sydnonimin hydrochloride (SIN-1, 2mgkg-') showed a decrease in bladder capacity, micturition volume and threshold pressure. SIN-1, but not SNP, induced spontaneous bladder contractions. 4 Isolated precontracted urethral preparations responded to electrical stimulation with a frequencydependent tetrodotoxin-sensitive relaxation. L-NAME (10-4 M), but not D-NAME, reduced the maximal relaxation to 31 ± 8% (n = 8) of the response prior to drug administration. The inhibition induced by L-NAME was completely reversed by L-arginine (10-3 M). SNP (10-1 10-4 M), SIN-1 (10-6-3 x l0-4 M) and NO (10-5-10-3M; present in acidified solution of NaNO2), caused relaxation (93-100%) of urethral preparations. L-NAME did not affect these relaxations.5 Detrusor strips contracted by carbachol or K' showed contractions in response to electrical stimulation, even when pretreated with a,p-methylene ATP and/or atropine. Small relaxations (14-41%) of detrusor strips were evoked by SNP (10-6-10-4M), SIN-1 (10-5-3 x 10-4M) and NO (10-5-10-3 M). Electrically (20 Hz) induced contractions of the detrusor muscle were unaffected by addition of L-NAME (10-6_10-4 M) or L-arginine (10-3 M).6 The present results suggest that the L-arginine/NO pathway is of functional importance for the bladder outlet region, but that its role in the detrusor is questionable. They also suggest that the site of action of L-NAME for inducing bladder hyperactivity in the rat is the outlet region rather than the detrusor muscle.

Association of lower urinary tract symptoms and erectile dysfunction: pathophysiological aspects and implications for clinical management

“…20 In another study, blockade of the NO pathway influenced the function of the lower urinary tract, as studied by cystometry in conscious rats and in vitro, in isolated muscle strips from the rat detrusor and urethra. 21 The theory that NO has a role in the development of LUTS is further supported by the characterization and functional relevance of PDE isoenzymes in the human prostate, urethra and bladder wall. 22 Importantly, this also opens the avenue toward a potential benefit of PDE5-inhibitor therapy in LUTS.…”

Characterization of nitric oxide synthase activity in sheep urinary tract: functional implications

“…A rich supply of nitrergic nerves has been identified by NADPH-diaphorase histochemistry and nitric oxide synthase (NOS) immunohistochemistry in the outflow region (urethra, bladder neck and bladder base or trigone) of several species including rat (McNeill et al, 1992), pig (Persson et al, 1993), sheep (Triguero et al, 1993) and human (Smet et al, 1994a;Leone et al, 1994). Furthermore, functional studies have demonstrated that isolated urethral and trigonal smooth muscles in all the species studied so far, respond to electrical field stimulation (EFS) with pronounced NANC relaxations, which can be blocked by NO synthesis inhibitors and mimicked by NO and NO donors (Garcia-Pascual et al, 1991;Andersson et al, 1991;Persson et al, 1992;1993;Garcia-Pascual & Triguero, 1994). This suggests that NO, or a related compound, is the relaxant mediator, which acts by increasing guanosine 3':5'-cyclic monophosphate (cyclic GMP) levels in smooth muscle (Garcia-Pascual & Triguero, 1994;Dokita et al, 1994).…”

“…It has been speculated that NO could have an inhibitory function, keeping the detrusor muscle relaxed during bladder filling (James et al, 1991), and that it could modulate ureteral peristalsis (Hernmndez et al, 1995). The presence of nerves containing the NO-synthesizing enzyme has been demonstrated, although in less density than in urethra, in the detrusor muscle of rat (McNeill et al, 1992), pig (Persson et al, 1993), sheep (Triguero et al, 1993) and human (Smet et al, 1994a) as well as in the muscular layer of the intravesical portion of the pig (Hernandez et al, 1995;Iselin et al, 1995) and human (Goessl et al, 1995) ureter, and in the human middle ureter (Smet et al, 1994b), while they were sparse in the pelvic pig ureter (Iselin et al, 1995) and absent in the distal ureter from sheep (Triguero et al, 1993 British Journal of Pharmacology (1996) 118, 905-914 A. Garcia-Pascual et al Nitric oxide synthase in urinary tract relaxations of neural origin sensitive to NOS inhibition have failed or only minor responses were obtained in both detrusor Persson et al, 1992;1993;Triguero et al, 1993) and ureteral preparations (Triguero et al, 1993;Obara et al, 1995;Iselin et al, 1995).NO is synthesized by NOS, a cytochrome P450-like haem protein that catalyses the NADPH-dependent oxidation of Larginine to form L-citrulline and NO. To date, three different NOS isoforms have been cloned and characterized which differ in their subcellular distribution, Ca2+-calmodulin dependency and regulation mechanisms (Knowles & Moncada, 1994).…”

The immediate effect of nitric oxide on the rabbit bladder after ovariectomy

“…The effects of NO on bladder muscle appear to be regional, since several studies have reported NOinduced relaxation of the urethra and bladder outlet, whereas the effect of NO on detrusor smooth muscle contraction or relaxation remains equivocal [4]. Intra-arterial administration of NO synthase inhibitor to conscious rats undergoing cystometry showed an increase in spontaneous bladder contractions [5]. In other hand, Bennett et al showed NOS inhibition decreased the magnitude and duration of reflex urethral relaxation but did not affect bladder contractility [6].…”