Comprehensive insight into functional interaction between GNB3 C825T and eNOS T-786C, G894T gene polymorphisms and association with susceptibility to diabetic erectile dysfunction.

BACKGROUND: No study has assessed the possible involvement of endothelial nitric oxide synthase (eNOS) T-786C and G894T and G-protein ß3 subunit (GNB3) C825T polymorphisms with susceptibility to diabetic vasculogenic erectile dysfunction (VED) in North African subjects. OBJECTIVES: Our aim was to evaluate the interaction and association between these gene polymorphisms and this disorder. MATERIALS AND METHODS: A total of 164 type 2 diabetes patients with VED diagnosed with penile color Doppler ultrasonography and 148 age-matched healthy volunteers were genotyped for the rs1799983 (G894T) and rs2070744 (T-786C) of the eNOS gene and the rs5443 (C825T) of the GNB3 gene using the PCR-RFLP method. RESULTS: A significant association of the eNOS G894T (p = 0.005) and T-786C (p = 0.02) with altered susceptibility to VED was observed. The risk also holds for the G894T and T-786C eNOS gene polymorphisms when excluding patients with dyslipidemia and cardiovascular diseases (p = 1.7·10-4 and p = 3.2·10-5 , respectively). The univariate odds ratio associated with CC alleles of the eNOS T-786C revealed a four times increased risk for VED (OR = 4.04; 95% CI = 1.53-10.67; p = 0.006). VED risk was also associated with the G894T variant under dominant model (p = 0.002) and the T-786C variant under recessive model (p = 0.004). Furthermore, the concomitant presence of the combined genotypes of the 894T and 786T strongly affected the predisposition to VED (p = 0.007). DISCUSSION AND CONCLUSION: Our study gave a comprehensive insight into functional interaction between GNB3 and eNOS gene polymorphisms and suggests that the eNOS G894T and T-786C variants are strong predisposing factors of VED susceptibility within men with type 2 diabetes.

Role of disturbed fatty acids metabolism in the pathophysiology of diabetic erectile dysfunction.

BACKGROUND: Vasculogenic erectile dysfunction (VED) is considered as a common complication among people with type 2 diabetes (T2D). We tested whether changes in fatty acid (FAs) classes measured in erythrocytes are associated with increased risk of diabetic VED along with related risk factors. METHODS: We assessed erythrocyte FAs composition, lipid peroxidation parameters and inflammatory cytokines among 72 T2D men with VED, 78 T2D men without VED and 88 healthy volunteers with similar age. Biochemical, hepatic, lipid and hormonal profiles were measured. RESULTS: T2D people with VED had significant decrease in the indexes of Δ6-desaturase and elongase activities compared to the other studied groups. The same group of participants displayed lower erythrocytes levels of dihomo-γ-linolenic acid (C20:3n-6) (P < .001), precursor of the messenger molecule PGE1 mainly involved in promoting erection. Moreover, absolute SFAs concentration and HOMA IR levels were higher in T2D people with VED when compared to controls and associated with impaired NO concentration (1.43 vs 3.30 ng/L, P < .001). Our results showed that IL-6 and TNF-α were significantly increased and positively correlated with MDA levels only in T2D people with VED (r = 0.884, P = .016 and r = 0.753, P = .035; respectively) suggesting a decrease in the relative availability of vasodilator mediators and an activation of vasoconstrictors release. CONCLUSION: Our findings show that the deranged FAs metabolism represents a potential marker of VED in progress, or at least an indicator of increased risk within men with T2D.

Are the Cavernous Tissue and Serum Levels of Micro RNAs 200a and 206 Elevated in Patients With Refractory Veno-occlusive Erectile Dysfunction? A Comparative Study.

OBJECTIVE: To evaluate the association between miRNAs and veno-occlusive erectile dysfunction. Recently, this association between miRNAs and erectile dysfunction was extensively studied using animal models. Our aim was to explore the miRNAs expressions and functions in the development of erectile dysfunction, especially veno-occlusive dysfunction, using a human tissue. PATIENTS AND METHODS: We prospectively recruited 60 patients with erectile dysfunction and controls between July 2015 and July 2016. The 30 patients had refractory veno-occlusive erectile dysfunction that was proven by investigations. They were scheduled for penile implant. The 30 controls were scheduled for repair of their fracture. We measured miRNAs (200a and 206) and nitric oxide in cavernous tissue and serum of both patients with erectile dysfunction and controls. RESULTS: A significant association was found between the 2 mentioned miRNAs and erectile dysfunction (P <.001). Mean level of nitric oxide in cavernous tissue of the controls was significantly higher than that in the patients (P <.001). miRNA 200a showed a cutoff value of 1.135 with 95% sensitivity and 100% specificity, whereas miRNA 206 showed a cutoff value of 1.125 with 100% sensitivity and 100% specificity. CONCLUSION: To the best of our knowledge, our study is the first report to measure the level of miRNAs in the cavernous tissue, using a human tissue. Furthermore, this study can be considered a good step of deploying miRNAs through a blood test to detect early negative changes that lead to erectile dysfunction. Finally, we recommend more studies to be conducted to better understand if these miRNAs are involved in the pathophysiology of veno-occlusive erectile dysfunction.

Alterations in microRNA expression in a murine model of diet-induced vasculogenic erectile dysfunction.

INTRODUCTION: MicroRNAs (miRs) are noncoding, endogenous RNA molecules that regulate gene expression and play roles in response to vascular injury. AIM: The aim of this study was to identify miRs expressed in corporal tissue (CT) and to determine whether miRs demonstrate differential expression in a mouse model of diet-induced erectile dysfunction (ED). METHODS: RNA was isolated from the CT from control mice and mice with diet-induced ED. A quantifiable miR profiling technique (NanoString) was used to determine the expression of over 600 miRs. MAIN OUTCOME MEASURES: Differential expression analysis was performed using a negative binomial regression model for count-based data. Mean expression levels, fold change, and false discovery-corrected P values were determined. Candidate miRs were validated via quantitative polymerase chain reaction (Q-PCR). RESULTS: In control mice, NanoString analysis revealed that 181 miRs were expressed above background levels and 5 miRs were expressed at high levels. Diet-induced ED resulted in the up-regulation of 6 miRs and the down-regulation of 65 miRs in the CT compared with mice on control diet. Focusing on the upregulated miRs, we chose five for Q-PCR validation. Of these five, two (miR-151-5p and miR-1937c) demonstrated significance via Q-PCR, whereas the other three (miR-720, miR-1937a, miR-205) trended in the correct direction. CONCLUSIONS: MiRs may play a significant role in mRNA regulation in CT and specific miRs may be involved in diet-induced vasculogenic ED. Future studies are aimed at determining the mRNA targets of these miRs.

Vascular regenerative therapies for the treatment of erectile dysfunction: current approaches.

The pharmacological treatment of erectile dysfunction (ED) is mainly represented by the administration of inhibitors of phosphodiesterase-5 (PDE5). However, in the clinical practice many patients do not benefit from such a treatment, hence the scientific interest extends to other therapeutic strategies; in particular, to the vascular regenerative therapy. This review describes the main acquisitions related to this approach represented by the mesenchymal stem cell or adipose tissue stem cell transplantation and endothelial nitric oxide synthase or vascular endothelial growth factor gene therapy. Moreover, there are other two aspects of wide interest represented by the potential vascular regenerative effects exerted by the PDE5 inhibitors and the therapeutic strategies for a category of patients who more frequently do not respond to the conventional treatment for ED, the patients with diabetes mellitus.

The neuroprotective effect of platelet-rich plasma on erectile function in bilateral cavernous nerve injury rat model.

INTRODUCTION: Neurogenic erectile dysfunction resulting from cavernous nerve (CN) injury is a major complication caused by radical prostatectomy. The use of platelet-rich plasma (PRP) on the nerve-injured site has shown promising results for the nerve regeneration. However, the effects of PRP injection in corpus cavernosum after bilateral CN injury have never been investigated. AIM: To assess the neuroprotective effect of PRP injection in corpus cavernosum after bilateral CN injury. METHODS: Male Sprague-Dawley rats were randomly divided into three groups: Group I underwent sham operation, while the remaining two groups underwent bilateral CN crush. Crush injury groups were treated at the time of injury with an application of PRP or normal saline only injection in the corpus cavernosum, respectively. Four weeks later, erectile function (EF) was assessed by CN electrosimulation, and CNs as well as penile tissue were collected for histology. MAIN OUTCOME MEASURES: Intracavernous pressure (ICP) monitored during electrical stimulation of CNs; myelinated axons number of CNs and dorsal penile nerve; collagen type change, number of apoptotic cells, and mRNA expression of caspase-3 and transforming growth factor-ß1 (TGF-ß1) in the corpus cavernosum. RESULTS: Four weeks after surgery, in the vehicle-only group, the functional evaluation showed a lower mean maximal ICP than that in the sham group (P < 0.05). PRP treatments resulted in significant recovery of EF, as compared with the vehicle-only group (P < 0.05). Histologically, the PRP-treated group had a significant preservation of myelinated axons of CNs compared with the vehicle-only group (P < 0.05) and reduced the apoptotic index. The mRNA expression of TGF-ß1 in the corpus cavernosum tissue was significantly decreased in the PRP group compared with the vehicle-only group (P < 0.05). CONCLUSIONS: PRP injection in the corpus cavernosum increased the number of myelinated axons and facilitated recovery of EF in the bilateral CN injury rat model.

Gene therapy with an erythropoietin enhancer-mediated, hypoxia-inducible gene expression system in the corpus cavernosum of mice with high-cholesterol diet-induced erectile dysfunction.

Cavernous hypoxia is an important factor in the pathogenesis of vasculogenic erectile dysfunction (ED). Therefore, the hypoxia-inducible gene expression system can be exploited as gene therapy for vasculogenic ED. This study was undertaken to examine the effectiveness of a hypoxia-inducible gene expression system, namely, the RTP801 promoter or the erythropoietin enhancer, in a mouse model of hypercholesterolemic ED in vivo and in primary cultured mouse cavernous endothelial cells in vitro. Two-month-old male C57BL/6 mice were fed a diet containing 4% cholesterol and 1% cholic acid, and age-matched control animals were fed a normal diet for 3 months. Mouse cavernous endothelial cells were isolated and cultured under normoxic or hypoxic conditions. After treatment of animals or endothelial cells with pSV-Luc, pRTP801-Luc, or pEpo-SV-Luc vector, gene expression was evaluated by luciferase assay, and the gene expression area was evaluated by immunohistochemistry. Plasmids pRTP801-Luc and pEpo-SV-Luc induced gene expression significantly in the hypercholesterolemic mice and in cavernous endothelial cells under hypoxia, and the highest gene expression was noted in the group treated with pEpo-SV-Luc. Gene expression was higher for more than 7 days in the hypercholesterolemic mice injected with pEpo-SV-Luc than in mice injected with pSV-Luc. As shown by immunohistochemistry, the gene expression area was also greater in the pEpo-SV-Luc group than in the pSV-Luc group, but the difference was not as great as that in luciferase activity. The hypoxia-specific gene expression system could be a valuable tool for facilitating gene delivery into ischemic corpus cavernosum tissue resulting from vascular causes.

Association of the T-786C, G894T and 4a/4b polymorphisms of the endothelial nitric oxide synthase gene with vasculogenic erectile dysfunction in Iranian subjects.

OBJECTIVE: • To investigate the association of the T-786C, G894T and variable number of tandem repeats (VNTRs) in intron 4 (a/b) polymorphisms of the eNOS gene in Iranian subjects with vasculogenic erectile dysfunction (ED). PATIENTS AND METHODS: • A total of 322 consecutive patients with vasculogenic ED were recruited. Patients with concomitant risk factors for ED were excluded. • Patients with ED were identified based on history-taking, detailed physical examination, serum biochemistry, sex hormone measurements, application of the International Index of Erectile Function (IIEF) questionnaire, and penile duplex Doppler ultrasonography after intracavernosal injection of 20 µg prostaglandin E(1) . The control group comprised 318 age-matched healthy male volunteers. • Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism and the T-786C, G894T and VNTR intron 4 polymorphisms of the eNOS gene were determined. RESULTS: • After multivariate regression analysis, significant differences were seen in the frequencies of genotypes and alleles of the two T-786C and G894T polymorphisms when patients with ED and normal controls were compared. • In a multiple logistic regression analysis, the odds ratio (OR) of increased ED was strongly associated with the -786C allele [adjusted OR = 3.12, 95% confidence interval (CI) = 2.28-4.25; P= 0.001] and the 894T allele (adjusted OR = 3.87, 95% CI = 2.53-4.87; P= 0.001). • The data showed a higher prevalence of the T-786C CC genotype (adjusted OR = 2.72, 95% CI = 1.88-3.65; P= 0.006), and the G894T GT (adjusted OR = 1.72, 95% CI 1.24-2.83; P= 0.037) and G894T TT genotypes (adjusted OR = 3.42, 95% CI 2.42-4.26; P= 0.001) in patients with ED than in the controls. CONCLUSIONS: • The findings of the present study suggest that the eNOS T-786C and G894T polymorphisms are strong predictors of the predisposition to ED in addition to traditional risk factors, signifying a genetic influence for this multifactorial disease. • Further studies in different ethnic populations are needed to better elucidate the role of eNOS gene polymorphism in the pathogenesis of ED.

Role of methylenetetrahydrofolate reductase gene polymorphisms (C677T, A1298C, and G1793A) in the development of early onset vasculogenic erectile dysfunction.

BACKGROUND AND AIMS: The methylenetetrahydrofolate reductase (MTHFR) gene plays a key role in the metabolism of folate and homocysteine (Hcy) and its mutations have been associated with high serum Hcy level. Elevated serum Hcy has been linked to impaired endothelial function and occlusive vascular disease. We studied the association among the different genotypes of all three MTHFR polymorphisms (C677T, A1298C, and G1793A) and the risk of early-onset vasculogenic erectile dysfunction (VED). METHODS: We performed a case-control study of 114 men with early-onset VED and 228 age-matched controls. Genotyping of MTHFR gene polymorphisms was performed using polymerase chain reaction restriction fragment length polymorphism (PCR-RLFP) technique. We also measured plasma lipids, Hcy, folate, and vitamin B12 levels. RESULTS: Patients with early-onset VED had higher serum Hcy levels (12.29 ± 2.32 vs. 9.82 ± 2.35 µmol/L, p = 0.001) and higher prevalence of 677TT homozygocity compared to controls (15.8% vs. 11.4%, p = 0.01). Serum Hcy concentration was significantly higher in individuals with 677TT, 1298CC, and 1793GG genotypes. Subgroup analysis according to severity of ED (mild, moderate, and severe) showed that patients with severe VED had higher serum Hcy levels compared to patients with mild VED (13.48 ± 2.51 vs. 11.21 ± 2.32 µmol/L, p = 0.001). CONCLUSIONS: Odds ratio seems to demonstrate that individuals with the MTHFR 677TT genotype and the 677TT + 1298AC combined genotype had a 3.16- and 3.89-fold increased risk for developing VED, suggesting a possible association of MTHFR polymorphisms with the risk of early-onset VED.

T-786C polymorphism in promoter of eNOS gene as genetic risk factor in patients with erectile dysfunction in Turkish population.

OBJECTIVES: To investigate the effect of 2 endothelial nitric oxide synthase gene polymorphisms, namely, variable number of 27-bp tandem repeats in intron 4 and T-786C in the promoter region, on the susceptibility to erectile dysfunction (ED) in Turkish population. METHODS: A total of 72 patients with ED (mean age 54.3 +/- 9.2 years) diagnosed by Doppler ultrasonography and 71 healthy controls (mean age 55.4 +/- 8.2 years) were analyzed. Genotypes were determined through polymerase chain reaction with or without restriction endonuclease digestions. RESULTS: Genotype distribution for CC genotype of T-786C polymorphism in promoter was significantly different between patients with ED and controls, the genotype frequency being 31.9% and 12.7%, respectively (P = .019). The univariate odds ratio (OR) associated with CC alleles revealed 3 times increased risk for ED (OR = 3.2; 95% confidence interval [CI], 1.4-7.6; P = .006). The risk also holds when excluding patients with hypertension and diabetes mellitus (P = .012, OR = 3.1; 95% CI, 1.2-7.7) as well as obesity (P = .05, OR = 4; 95% CI, 1.05-15.3). Patients with CC genotype of promoter present earlier symptoms of ED (51.7%) compared with controls (10.7%) (P <.001). No significant correlation was observed with variable number of tandem repeats in intron 4 and with the type of vascular insufficiency. CONCLUSIONS: The CC genotype of T-786C polymorphism in the promoter of eNOS gene is associated with increased risk of ED in Turkish population. Earlier onset of ED with CC genotype suggests that CC allele is an independent risk factor for endothelial dysfunction in the absence of other risk factors (hypertension, diabetes mellitus, obesity). An impaired NO production because of CC alleles may account for pathophysiology of ED.

Treatment of erectile dysfunction due to C677T mutation of the MTHFR gene with vitamin B6 and folic acid in patients non responders to PDE5i.

INTRODUCTION: Epidemiological studies conducted on erectile dysfunction (ED) have demonstrated its close correlation with cardiovascular disease. Since hyperhomocysteinemia is considered an important cardiovascular risk factor, it could also be involved in the pathogenesis of ED. AIM: To study the role of the C677T MTHFR mutation with subsequent hyperhomocysteinemia in the determination of ED. METHODS: We studied 75 consecutive patients presenting with ED. Patients were interviewed using the International Index of Erectile Function. Blood samples were drawn for determination of MTHFR gene C677T mutation, homocysteine (Hcy) and folate levels. Penile color Doppler was also performed. MAIN OUTCOME METHODS: Patients were administered sildenafil citrate for 2 months. The nonresponders were treated with combination of sildenafil, vitamin B6, and folic acid for 6 weeks. Patients were split into three groups, A, B, and C on the basis on their MTHFR genotype, and in a further group defined as "sildenafil nonresponders" (NR). RESULTS: We found 20 patients homozygous for mutant MTHFR 677T, 36 heterozygous, and 19 wild type. Difference in baseline values for Hcy and folic acid was found between groups A and B, and A and C. The NR group (18 patients from group A and B), presented high levels of Hcy and low levels of folic acid. After combination treatment 16 of them (88.9%) revealed an improvement in the IIEF questionnaire. Moreover, it was measured a significant difference between the values of Hcy and folic acid at the baseline and at the end of the study for the nonresponders. CONCLUSIONS: Hyperhomocysteinemia in patients homozygotes for the C677T mutation may interfere with erection mechanisms and thus be responsible for ED. In case of hyperhomocysteinemia associated with low levels of folates, the administration of PDE5 inhibitors may fail if not preceded by the correction of the alterated levels of Hcy and folates.

The associations among eNOS G894T gene polymorphism, erectile dysfunction, and benign prostate hyperplasia-related lower urinary tract symptoms.

INTRODUCTION: A number of literature has now identified the role of impaired nitric oxide synthase/nitric oxide pathway in the endothelium as the central to the development of erectile dysfunction (ED) and benign prostate hyperplasia-related lower urinary tract symptoms (BPH/LUTS). Recently a few studies have reported the associations between endothelial nitric oxide synthase (eNOS) G894T gene polymorphisms and ED. However, there has been no report investigating the eNOS G894T genetic susceptibility factor for both ED and BPH/LUTS. AIM: To investigate the possible associations among eNOS G894T polymorphism, ED, and BPH/LUTS in a Taiwanese population. MAIN OUTCOME MEASURES: Patients with ED were defined as those having a 5-item International Index of Erectile Function-5 <21. METHODS: In all, 372 Taiwanese men underwent a free health screening were enrolled. All the men had complete clinical data and questionnaires taken. The eNOS G894T polymorphisms were determined using the polymerase chain reaction-restriction fragment length polymorphism method. RESULTS: Three hundred seventy-two men had a mean (standard deviation) age of 60.2 (8.8) years. With multivariate analysis, our data identified that aging, diabetes mellitus (DM), and eNOS G894T gene polymorphism were three independent common risk factors for both ED and BPH/LUTS (P < 0.001, P = 0.036, and P = 0.039 for ED; P = 0.034, P = 0.004, and P = 0.016 for BPH/LUTS, respectively). The eNOS 894T allele carriers had significantly higher prevalence of ED (77.9% vs. 60.4%, P = 0.012) and higher International Prostate Symptom score (IPSS) (13.3 +/- 10.7 vs. 9.3 +/- 7.8, P = 0.001) than G allele carriers. CONCLUSIONS: Our results showed that aging, DM, and eNOS 894T allele carrier gene polymorphism were the three independently common risk factors for both ED and BPH/LUTS in the Taiwanese population. The eNOS 894T allele carriers had significantly higher frequencies of ED and higher IPSS, suggesting that eNOS G894T gene polymorphisms may play an implication as a genetic susceptibility factor for both ED and BPH/LUTS.

Derangements in endothelial cell-to-cell junctions involved in the pathogenesis of hypercholesterolemia-induced erectile dysfunction.

INTRODUCTION: Endothelial cell-to-cell junctions are crucial for vascular formation, networking, and remodeling of blood vessels as well as for inducing and integrating intracellular signals. AIM: We investigated the differential expression and distribution of endothelial cell-to-cell junction proteins in the penis of mice with hypercholesterolemia-induced erectile dysfunction. METHODS: Two-month-old C57BL/6J mice were fed a diet containing 4% cholesterol and 1% cholic acid, and age-matched control animals were fed a normal diet, for 3 months. We performed dual priming oligonucleotide (DPO)-based multiplex polymerase chain reaction (PCR) (Seegene, Seoul, Korea) to screen the differential gene expression of 21 endothelial cell-to-cell junctions. MAIN OUTCOME MEASURES: At 5 months, erectile function was measured by electrical stimulation of the cavernous nerve, and the penis was harvested and stained with antibody to claudin-5, vascular endothelial (VE)-cadherin, and platelet/endothelial cell adhesion molecule (PECAM)-1 (N = 8 per group). Cavernous specimens from a separate group of animals were used for claudin-5, VE-cadherin, and PECAM-1 reverse transcriptase-PCR and Western blot analysis. RESULTS: Erectile function was significantly lower in hypercholesterolemic mice than in controls. DPO-based multiplex PCR revealed a profound decrease in the gene expression of endothelium-specific cell-to-cell junction proteins, including claudin-5, VE-cadherin, and PECAM-1, in hypercholesterolemic mice compared with that in controls. The expression of claudin-5, VE-cadherin, and PECAM-1 protein evaluated by Western blot or immunohistochemistry was significantly lower in hypercholesterolemic mice than in controls. These endothelial cell-to-cell junction proteins were more sparsely distributed in the endothelium of cavernous sinusoids than in the endothelium of cavernous artery and dorsal blood vessels. CONCLUSION: Down-regulation of the endothelial cell-to-cell junctions and decreased endothelial content in the corpus cavernosum might play a major role in the deterioration of erectile function in hypercholesterolemic mice.

[Single base polymorphisms and erectile dysfunction]. / Einzelbasenpaarpolymorphismen und erektile Dysfunktion.

The risk for erectile dysfunction is closely linked to cardiovascular morbidities such as coronary heart disease, arterial hypertension, hypercholesterolemia, and diabetes. Molecular analysis revealed an association between the genotypes in single base polymorphisms and the risk for these cardiovascular morbidities. In this review the current knowledge of association studies of single nucleotide polymorphisms and erectile dysfunction and the response to the PDE-5 inhibitor sildenafil is described.

Gene expression profiling of an arteriogenic impotence model.

Penile arterial insufficiency is one of the most common causes of ED. We have established a traumatic arteriogenic insufficiency rat model by the ligation of the pudendal arteries. To simulate both acute and chronic traumatic injuries, five ligation periods (6 h, 3 days, 7 days, 3 weeks, and 6 weeks) were chosen. By electrostimulation of the cavernous nerve, the intracavernous pressure was determined to be between 20 and 40-cm H(2)O for the ligated rats compared to around 100-cm H(2)O for the control rats. The erectile tissue in the corpus cavernosum of these rats was then subjected to microarray analysis, in which an array that contains cDNA fragments representing 1176 rat genes was used. The results demonstrated that normal rat corpus cavernosum expressed approximately 200 genes at detectable levels and that ligation produced differential expression of approximately 25 genes, depending on the duration of ligation. The most highly ligation-induced gene was apolipoprotein D (ApoD), with peak expression in the 3- and 7-day ligated rats. Three of the insulin-like growth factor binding proteins (IGFBP-1, 3, and 5) were upregulated in all ligated rats. IGFBP-6, which was one of the most highly expressed genes in the normal corpus cavernosum, was down-regulated in all ligated rats. Cysteine proteases of the cathepsin family were also differentially expressed between control and ligated rats, with cathepsin K being down-regulated most. A few genes were upregulated only in the 6-week ligated rats, including angiotensin-converting enzyme. Finally, VEGF, whose induction has been identified in many other ischemic tissues, was not induced in corpus cavernous tissue of ligated rats.