Avaliação do efeito relaxante do BAY 41-2272 em detrusor isolado de coelhos / Evaluation of relaxant effect of BAY 41-2272 in rabbit isolated detrusor

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Overactive bladder (OAB) is a highly prevalent condition that affects millions of people worldwide with a profound effect on quality of life. The bladder overactivity is related to spontaneous contractions of the detrusor smooth muscle causing an increase in the intravesical pressure and consequently stimulation of the micturirion reflex. Evidences suggest that impairment of nitric oxide (NO) signaling pathway may account for OAB. It is well established that NO signaling pathways involves soluble guanylate cyclase (sGC) stimulation and cyclic GMP production. Recently, pharmacological agents capable of directly stimulating soluble guanylate cyclase independenly of NO, such as BAY 41-2272 has been reported to produce relaxation of different types of smooth muscle, showing great therapeutic potential in disturbs which NO pathway is impaired. The present study aimed to evaluate the capacity of BAY 41-2272 to relax isolated mouse, rat and rabbit DSM and the mechanism underlying these response. C57b6 male mice, Wistar male rats and New Zealand male rabbits were anesthetized, and urinary bladder removed. DSM was transferred to 10-mL organ baths containing oxygenated and warmed Krebs-Henseleit solution. Tissues were connected to force-displacement transducers and changes in isometric force were recorded. Concentration-response curves to BAY 41-2272 (10-9 - 10-4M) were constructed, in previously contracted tissues with carbachol (10 µM) or KCl (80 mM), in the absence and in the presence of L-NAME (Nitric Oxide Synthase inhibitor; 100 µM), ODQ (sGC inhibitor; 100 µM), Sildenafil (phosphodiesterase type-5 inhibitor; 10 µM), or potassium channel blockers (0.1 µM charybdotoxin + 1 µM apamin; 1 µM tetraethylammonium; or 10 µM glybenclamide). Concentration-response curves to sodium nitroprusside (SNP; 10-8 - 10-4 M), glyceryl trinitrate (GTN; 10-8 - 10-4 M) and 8Br-cGMP (10-8 - 10-4 M) were also constructed. CaCl2-induced contractions in DSM and calcium influx in rabbit isolated platelets were evaluated in the presence of BAY 41-2272. Levels of cAMP and cGMP in DSM strips were determined after treatment with BAY 41-2272 (10 and 100 µM), SNP (100 µM) in the absence or in the presence of ODQ (100 µM) using specific EIA kit. BAY 41-2272 (0.001-100 µM) produced concentration-dependent DSM relaxations in mouse, rat and rabbit with maximal responses of 61.3 ± 6.6%, 95.1 ± 9.9% and 91.7 ± 5.9%, respectively. The NO-donors sodium nitroprusside and glyceryl trinitrate, as well as 8-bromo-cGMP also produced concentration-dependent rabbit DSM relaxations, but to a lesser extent than BAY 41-2272. Pretreatment with L-NAME (NO synthesis inhibitor) or sildenafil (phosphodiesterase-5 inhibitor) had no effect in BAY 41-2272- induced responses. However, the soluble guanylyl cyclase inhibitor ODQ significantly reduced BAY 41-2272-induced relaxantions. BAY 41-2272 (10 and 100 µM) increased the bladder cGMP levels by about of 14- and 20-fold, respectively, without affecting the cAMP levels. The cGMP increases in response to BAY 41-2272 and SNP were markedly reduced by ODQ. CaCl2 caused a concentration-dependent contraction in DSM strips and BAY 41- 2272 significantly reduced the contractile responses to extracellular Ca2+ in an ODQinsensitive manner. BAY 41-2272 also significantly reduced the increase of intracellular calcium levels induced by thrombin. This inhibitory effect was completely reverted after the treatment with ODQ. BAY 41-2272 relaxes DSM of the three animal species studied. BAY 41-2272-induced DSM relaxation involves mainly cGMP production, but an additional mechanism involving Ca2+ influx blockade independently of cGMP production appears to be involved

ASSUNTO(S)

nitric oxide gmp ciclico bexiga cyclic gmp oxido nitrico urinary baldder

ACESSO AO ARTIGO

Documentos Relacionados