Calcium dobesilate potentiates endothelium-derived hyperpolarizing factor-mediated relaxation of human penile resistance arteries

Abstract

1 We have evaluated the participation of endothelium-derived hyperpolarizing factor (EDHF) in the endothelium-dependent relaxation of isolated human penile resistance arteries (HPRA) and human corpus cavernosum (HCC) strips. In addition, the effect of the angioprotective agent, calcium dobesilate (DOBE), on the endothelium-dependent relaxation of these tissues was investigated. 2 Combined inhibition of nitric oxide synthase (NOS) and cyclooxygenase (COX) nearly abolished the endothelium-dependent relaxation to acetylcholine (ACh) in HCC, while 60% relaxation of HPRA was observed under these conditions. Endothelium-dependent relaxation of HPRA resistant to NOS and COX inhibition was prevented by raising the extracellular concentration of K(+) (35 mM) or by blocking Ca(2)(+)-activated K(+) channels, with apamin (APA; 100 nM) and charybdotoxin (CTX; 100 nM), suggesting the involvement of EDHF in these responses. 3 Endothelium-dependent relaxation to ACh was markedly enhanced by DOBE (10 micro M) in HPRA but not in HCC. The potentiating effects of DOBE on ACh-induced responses in HPRA, remained after NOS and COX inhibition, were reduced by inhibition of cytochrome P450 oxygenase with miconazole (0.3 mM) and were abolished by high K(+) or a combination of APA and CTX. 4 In vivo, DOBE (10 mg kg(-1) i.v.) significantly potentiated the erectile responses to cavernosal nerve stimulation in male rats. 5 EDHF plays an important role in the endothelium-dependent relaxation of HPRA but not in HCC. DOBE significantly improves endothelium-dependent relaxation of HPRA mediated by EDHF and potentiates erectile responses in vivo. Thus, EDHF becomes a new therapeutic target for the treatment of erectile dysfunction (ED) and DOBE could be considered a candidate for oral therapy for ED.

Figure 1

Effects of combined inhibition of NOS and COX with L-NNA; 100 μM) and INDO (5 μM), respectively, on the endothelium-dependent relaxation induced by ACh (1 nM–10 μM) on phenylephrine-contracted HCC strips (a) and norepinephrine-contracted HPRA (b). Data are expressed as mean±s.e.m. of the percentage of total relaxation induced by 0.1 mM papaverine. n Indicates the number of patients from whom the tissues were collected for the experiments. ^***Indicates P<0.005 vs control responses by a two-factor ANOVA test.

Figure 2

Effects of high extracellular K⁺ concentration (35 mM) and Ca₂⁺-activated K⁺-channel blockade with APA; (100 nM) and CTX; (100 nM) in addition to combined inhibition of NOS and COX with L-NNA; (100 μM) and INDO (5 μM), respectively, on the endothelium-dependent relaxation induced by ACh (1 nM–10 μM) on norepinephrine-contracted HPRA. Data are expressed as mean±s.e.m. of the percentage of total relaxation induced by 0.1 mM papaverine. n Indicates the number of patients from whom the tissues were collected for the experiments. ^***Indicates P<0.005 vs control responses by a two-factor ANOVA test.

Figure 3

Effects of the treatment with DOBE (10 μM) on the endothelium-dependent relaxation induced by ACh (1 nM–10 μM) on phenylephrine-contracted HCC strips (a) and norepinephrine-contracted HPRA (b). Data are expressed as mean±s.e.m. of the percentage of total relaxation induced by 0.1 mM papaverine. n Indicates the number of patients from whom the tissues were collected for the experiments. ^***Indicates P<0.005 vs control responses by a two-factor ANOVA test.

Figure 4

Effects induced by DOBE (10 μM) on the endothelium-dependent relaxation induced by ACh (1 nM–10 μM) on phenylephrine-contracted HCC strips (a) and norepinephrine-contracted HPRA (b) after combined inhibition of NOS and COX with L-NNA (100 μM) and INDO (5 μM), respectively. (c) shows the comparison of ACh-induced responses in HPRA treated with DOBE (10 μM) in the presence or the absence of L-NNA (100 μM) plus INDO (5 μM). Data are expressed as mean±s.e.m. of the percentage of total relaxation induced by 0.1 mM papaverine. n Indicates the number of patients from whom the tissues were collected for the experiments. ^***Indicates P<0.005 vs control curve by a two-factor ANOVA test.

Figure 5

Effects induced by DOBE (10 μM) on the endothelium-dependent relaxation induced by ACh (1 nM–10 μM) on norepinephrine-contracted HPRA exposed to high extracellular K⁺ concentration (35 mM). Data are expressed as mean±s.e.m. of the percentage of total relaxation induced by 0.1 mM papaverine. n Indicates the number of patients from whom the tissues were collected for the experiments.

Figure 6

Effects of Ca₂⁺-activated K⁺-channel blockade with APA (100 nM) and CTX (100 nM) on the effects induced by DOBE (10 μM) on the endothelium-dependent relaxation induced by ACh (1 nM–10 μM) on norepinephrine-contracted HPRA in the presence of L-NNA (100 μM) plus INDO (5 μM). Data are expressed as mean±s.e.m. of the percentage of total relaxation induced by 0.1 mM papaverine. n Indicates the number of patients from whom the tissues were collected for the experiments. ^***Indicates P<0.005 vs DOBE alone by a two-factor ANOVA test.

Figure 7

Influence of cytochrome P450 oxygenase inhibition with miconazole (0.3 mM) on the effects induced by DOBE (10 μM) on the endothelium-dependent relaxation induced by ACh (1 nM–10 μM) on norepinephrine-contracted HPRA in the presence of L-NNA (100 μM) plus INDO (5 μM). Data are expressed as mean±s.e.m. of the percentage of total relaxation induced by 0.1 mM papaverine. n Indicates the number of patients from whom the tissues were collected for the experiments. ^***Indicates P<0.005 vs DOBE alone by a two-factors ANOVA test.

Figure 8

Effects of i.v. administration of DOBE (10 mg kg⁻¹) on erectile responses to cavernosal nerve electrical stimulation (CNES) in anesthetized male rats. Data are expressed as the mean±s.e.m. of the peak of ICP increase to CNES normalized by MAP values (a), the duration of the response to CNES (b) and the AUC ( mmHgs) of ICP increase to CNES normalized by MAP values (c). ^*P<0.05, ^**P<0.01, ^***P<0.005 vs control frequency–response curve by a two-factors ANOVA test.