Iñigo Sáenz de Tejada

Impaired Neurogenic and Endothelium-Mediated Relaxation of Penile Smooth Muscle from Diabetic Men with Impotence

Relaxation of the smooth muscle of the corpora cavernosa of the penis is necessary for penile erection. To determine the relation of impaired relaxation to impotence in diabetic patients, we performed an in vitro examination of corpus cavernosum tissue obtained at the time of implantation of a penile prosthesis in 21 diabetic and 42 nondiabetic men with impotence. Contraction was induced in isolated strips of corporal smooth muscle by norepinephrine; then relaxation was assessed with electrical stimulation of autonomic nerves and with the administration of three agents: acetylcholine, which is known to be mediated by endothelium-derived relaxing factor; papaverine; and sodium nitroprusside. The latter two act directly on smooth muscle (i.e., they are endothelium-independent). Autonomically mediated relaxation with electrical stimulation was less pronounced in the smooth muscle from diabetic men (n = 18) than in the smooth muscle from nondiabetic men (n = 24; P = 0.001). The degree of impairment increased with the duration of diabetes (r = 0.61, P = 0.007). Endothelium-dependent relaxation was also impaired, as evidenced by a lower degree of muscle relaxation after the administration of acetylcholine in the tissue from diabetic men (n = 16) than in that from nondiabetic men (n = 22; P = 0.001). The adverse effects of diabetes persisted after we controlled for smoking and hypertension. Endothelium-independent relaxation after the administration of nitroprusside and papaverine was similar in tissue from the diabetic and nondiabetic men. We conclude that diabetic men with impotence have impairment in both the autonomic and the endothelium-dependent mechanisms that mediate the relaxation of the smooth muscle of the corpora cavernosa. These findings may provide a rationale for the treatment of diabetic men with impotence by intracavernosal injection of vasodilators to induce endothelium-independent relaxation of the smooth muscle.

Investigative Urology: PGE sub 1 Suppresses the Induction of Collagen Synthesis by Transforming Growth Factor-beta sub 1 in Human Corpus Cavernosum Smooth Muscle

Collagen synthesis has been examined in primary cultures of human corpus cavernosum smooth muscle cells (HCCSMC), the major mesenchymal cell type of the corpus cavernosum. These cultures were grown from human surgical specimens and characterized by morphological and biochemical characteristics. These cells express mRNA for transforming growth factor-beta 1 (TGF-beta 1), a major regulator of extracellular matrix synthesis, as well as all three subtypes of TGF-beta receptors. Human corpus cavernosum smooth muscle cells primarily synthesize types I and III fibrillar collagen. Treatment of HCCSMC with exogenous TGF-beta 1 (80 pM.) induced a 2.5- to 4.5-fold increase in the synthesis of types I and III collagen and resulted in detectable levels of type V/XI collagen. Treatment of HCCSMC with the eicosanoid PGE1 in combination with TGF-beta 1 suppressed the induction of collagen synthesis by TGF-beta 1 in a dose-dependent manner with concomitant decreases in types I, III and V/XI collagen. The expression of TGF-beta 1 mRNA as well as types I and II TGF-beta receptors was induced by exogenous TGF-beta 1. Transforming growth factor-beta 1 mRNA induction was suppressed by PGE1. These data suggest that prostaglandins and TGF-beta 1 may play a key role in modulation of collagen synthesis in the corpus cavernosum, and in the regulation of fibrosis of the corpus cavernosum.

Mechanisms of Venous Leakage: A Prospective Clinicopathological Correlation of Corporeal Function and Structure

PURPOSE We investigated the pathophysiology of structurally based corporeal veno-occlusive dysfunction. MATERIALS AND METHODS We prospectively evaluated 24 impotent patients (mean age plus or minus standard error 46 +/- 3 years) who had exposure to vascular risk factors and/or disorders inducing diffuse trabecular structure alterations and who underwent penile prosthesis insertion. Preoperative indexes of veno-occlusive function (flow to maintain, venous outflow resistance and pressure decay measurements using repeat dosing pharmacocavernosometry) were correlated with postoperative erectile tissue computer assisted color histomorphometry (percent trabecular smooth muscle to total erectile tissue area). To develop further study findings and correlate histomorphometric findings with molecular biological properties molecular biological studies (ribonuclease protection analysis, reverse transcription-polymerase chain reaction assay for expression of transforming growth factor-beta 1 messenger [m] ribonucleic acid [RNA] and protein affinity labeling techniques for specific transforming growth factor-beta receptors) were performed in representative patients with high (39 to 43%), intermediate (30 to 37%) and low (13 to 29%) trabecular smooth muscle content (normal 42 to 50%). RESULTS Flow to maintain, venous outflow resistance and pressure decay values significantly correlated with trabecular smooth muscle cell content (r = -0.89, 0.82 and -0.85, respectively). In the high, intermediate and low smooth muscle content subgroups flow to maintain, venous outflow resistance and pressure decay values were 1 to 5, 9 to 30 and 50 to 120 ml. per minute, 17 to 84, 3 to 9 and 1 to 2 mm. Hg/ml. per minute, and 40 to 60, 48 to 80 and 110 to 120 mm. Hg decrease in 30 seconds from 150 mm. Hg, respectively. There were no significant differences in patient age or prevalence of risk factors among the 3 subgroups. Patients representative of all 3 subgroups had transforming growth factor-beta 1 mRNA, auto-induction of transforming growth factor-beta 1 mRNA and induction and/or increased availability of all 3 types of transforming growth factor-beta receptors. CONCLUSIONS The pathophysiology of structurally based corporeal veno-occlusive dysfunction is related to elevated corporeal connective tissue content. Based on our data and those in the literature corporeal fibrosis is hypothesized to develop secondary to abnormalities in the regulation of normal collagen synthesis and degradation, most likely associated with adverse influences of chronic ischemia.

Endothelium-derived nitric oxide and cyclooxygenase products modulate corpus cavernosum smooth muscle tone

Relaxation of penile corpus cavernosum smooth muscle is controlled by nerve and endothelium derived substances. In this study, endothelium-dependent relaxation of corporal smooth muscle was characterized and the role of arachidonic acid products of cyclooxygenase in endothelium-dependent relaxation was examined. Endothelium removal from rabbit corpora was performed by infusion with 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate and was confirmed by transmission electron microscopy. Strips of human and rabbit corporal tissues were studied in the organ chambers for isometric tension measurement. The accumulation of cyclic guanosine monophosphate (cGMP) and the release of eicosanoids from corporal tissue was measured by radioimmunoassay and correlated to smooth muscle relaxation. Our study showed that relaxation of corpus cavernosum tissue to acetylcholine, bradykinin and substance P was endothelium-dependent; potentiated by indomethacin; and inhibited by NG-monomethyl-L-arginine, methylene blue or LY83583. Relaxation to papaverine and sodium nitroprusside was endothelium-independent, and unaffected by NG-monomethyl-L-arginine. Relaxation to vasoactive intestinal polypeptide was partially endothelium-dependent; potentiated by indomethacin; attenuated by NG-monomethyl-L-arginine or methylene blue. The tissue level of cGMP was enhanced by acetylcholine and nitric oxide. Methylene blue inhibited both basal and drug-stimulated levels of cGMP. The release of eicosanoids was enhanced by acetylcholine and blocked by indomethacin. In conclusion, nitric oxide or a closely related substance accounts for the activity of endothelium-derived relaxing factor in the corporal tissue. Inhibition of the release of eicosanoids potentiates the relaxing effect of nitric oxide. Nitric oxide increases tissue cGMP which appears to modulate corporal smooth muscle relaxation.

Hypercholesterolemia Impairs Endothelium-Dependent Relaxation of Rabbit Corpus Cavernosum Smooth Muscle

The majority of cases of impotence are associated with vascular risk factors such as diabetes, hypercholesterolemia, hypertension and smoking. These factors induce impairment of endothelium-dependent relaxation of blood vessels in man and in experimental animals. In this study the effects of hypercholesterolemia on the reactivity of rabbit corpus cavernosum smooth muscle strips to endothelium-dependent and endothelium-independent agents were investigated. New Zealand White rabbits (n = 14) were randomly divided into control and treatment groups. The control group (n = 7) received a regular diet while the treatment group (n = 7) was fed a diet of 0.5% cholesterol and 4% peanut oil for 10 weeks. Animals were then sacrificed and the corporal tissue studied in organ chambers for isometric tension measurement. Tissue was contracted with phenylephrine and concentration-dependent relaxation to acetylcholine, in the presence and absence of indomethacin, and to nitroprusside were examined. Blood level of cholesterol in the cholesterol-fed group was significantly higher compared to the control group. Contractions to phenylephrine were similar in both groups. Hypercholesterolemia, however, inhibited relaxation to acetylcholine but did not alter relaxation to nitroprusside, a cyclic guanosine monophosphate (cGMP)-dependent, direct smooth muscle dilator. Indomethacin enhanced the relaxations to acetylcholine in both control and cholesterol-fed groups but did not correct the difference in the relaxation to acetylcholine between both groups. It is concluded that hypercholesterolemia impairs endothelium-mediated relaxation of rabbit corpus cavernosum smooth muscle. The mechanism for the endothelial dysfunction does not appear to involve alteration in cyclooxygenase products of arachidonate or the cGMP-dependent relaxation of corporal smooth muscle. Impairment of endothelium-dependent relaxation of corporal smooth muscle may contribute to the pathophysiology of impotence associated with hypercholesterolemia in man.

Diabetes Mellitus Impairs Neurogenic and Endothelium-Dependent Relaxation of Rabbit Corpus Cavernosum Smooth Muscle

The effect of alloxan-induced diabetes on the reactivity of corporeal nerves, endothelium and smooth muscle was studied in the New Zealand white rabbit. Fifteen rabbits were randomly divided into treated (n = 6) and control (n = 9) groups. The treated group was maintained for 6 weeks. Two control groups were studied. One control group (n = 3) was maintained for 6 weeks as littermate controls for diabetic group. The second control group (n = 6) was not maintained but was weight matched with the 6 week diabetic group. The reactivity of corpus cavernosum tissue from the diabetic animals and the control animals was studied in organ chambers. When tissue contraction was produced with phenylephrine for the study of relaxation to various stimuli, the tension induced was similar in the diabetic and the control groups. Relaxation of corpus cavernosum tissue to electrical stimulation of autonomic nerves as well as relaxation to the endothelium-dependent vasodilator acetylcholine were comparably unaffected in the weight matched and littermate control groups while significantly inhibited in the diabetic group. Treatment of the corporeal tissue with the cyclooxgenase inhibitor indomethacin enhanced the relaxation to electrical stimulation and to acetylcholine in the control and in the diabetic groups but did not improve the significant difference in relaxation between the two groups. Relaxation of corporeal tissue to endothelium-independent vasodilators, papaverine and nitroprusside was similar in the control groups and the diabetic groups. It is concluded that diabetes impairs neurogenic and endothelium-mediated relaxation of rabbit corpus cavernosum smooth muscle. These findings are comparable to those described in corpus cavernosum tissue from diabetic men, showing the validity of this experimental animal model. The mechanism for the nerve or endothelial dysfunction does not appear to involve alteration in cyclooxygenase products of arachidonate or the ability of the corporeal smooth muscle to relax via a cGMP-dependent mechanism. Since nitric oxide has been shown to act as the nonadrenergic noncholinergic neurotransmitter as well as endothelium-derived relaxing factor (EDRF) of the trabecular smooth muscle, it is possible that impairment of neurogenic and endothelium-dependent relaxation due to diabetes is mediated by alteration in the synthesis or availability of nitric oxide in corporeal tissue.

Regulation of Adrenergic Activity in Penile Corpus Cavernosum

The regulation of adrenergic activity in the penis was investigated by studying human and rabbit corpus cavernosum strips in organ chambers and measuring the release of norepinephrine from adrenergic nerve terminals. Electrical field stimulation of corporal strips caused frequency-dependent contractions which were potentiated by cocaine and attenuated by the alpha 1 adrenoceptor antagonist prazosin (10(-7) M), but not by the alpha 2 adrenoceptor antagonist rauwolscine (10(-7) M). Norepinephrine caused concentration-dependent contractions of corporal strips, which were attenuated by prazosin and rauwolscine. Acetylcholine and physostigmine attenuated adrenergic nerve mediated contractions and also significantly reduced electrically-induced norepinephrine release. These effects were reversed by atropine. Atropine alone enhanced electrically-induced norepinephrine release. Rauwolscine inconsistently enhanced adrenergic nerve mediated contractions but augmented norepinephrine release caused by electrical stimulation. The alpha 2 adrenoceptor agonist clonidine inhibited electrically-induced norepinephrine release. Vasoactive intestinal polypeptide (VIP) attenuated adrenergically-mediated contractions, but had no effect on electrically-induced release of norepinephrine. It is concluded that: 1) contraction of corporal smooth muscle is mediated by postjunctional alpha 1 adrenoceptors; 2) adrenergic activity is modulated by prejunctional alpha 2 adrenoceptors and cholinergic nerves via prejunctional muscarinic receptors; and 3) the putative nonadrenergic noncholinergic neurotransmitter, VIP, has no apparent role in the regulation of adrenergic nerves.

Traumatic Laceration of Intracavernosal Arteries: The Pathophysiology of Nonischemic, High Flow, Arterial Priapism

Two forms of priapism are known to occur. The more common type, veno-occlusive priapism, presents with a prolonged painful erection, and it is characterized by ischemia and pooling of blood within the corpora cavernosa. The less common form, high flow priapism, is characterized by lack of pain and ischemia. The pathophysiology of this disorder is poorly understood and the treatment is unclear. We report 2 cases of nonischemic priapism, one of which occurred after blunt perineal trauma and the other after intracavernosal self-injection with papaverine and phentolamine. Based on our 2 cases as well as a review of the literature (5 cases), we propose that the pathophysiological mechanism of this disorder is unregulated arterial inflow into the corpora, classify it as arterial priapism, and describe a diagnostic and therapeutic algorithm for its management.

Arterial Priapism: Diagnosis, Treatment and Long-Term Followup

We report on the long-term followup of 7 patients 11 to 50 years old treated for arterial priapism following perineal or penile trauma with arteriographic evidence of contrast medium extravasating from a lacerated cavernous artery into surrounding erectile tissue lacunae (an arterial-lacunar fistula). All patients underwent medical record review and completed a mailed questionnaire. The priapism erections were described as devoid of pain or tenderness, incompletely but constantly rigid and able to increase rigidity with sexual stimulation. Bright red corporeal aspirates were observed in all cases. Color flow Doppler ultrasound findings of focal areas of high flow turbulence correlated with diagnostic arteriography (correlation coefficient 1.00). Initial treatment by mechanical or pharmacological means was unsuccessful when performed. Superselective transcatheter embolization of the ipsilateral common penile artery resolved the priapism in all cases. The interval from onset to resolution of priapism was 4 to 126 days. Full erectile function return was delayed from 2 weeks to 5 months, most likely from resolving clot lysis. Full erection quality was restored in 6 of 7 patients with persistent function and restored frequency of intercourse at 6 to 67 months. Reestablished cavernous artery flow in previously embolized arteries was demonstrated on followup ultrasonography. Surgical treatment was not required in any case. We conclude that arterial priapism occurs in the absence of neurogenic-mediated relaxation, and is sustained by high oxygen tension and shear stress associated with the cavernous artery laceration. Embolization therapy offers effective management of the pathophysiology with high preservation of premorbid erectile function.

Possible role of Na+‐K+‐ATPase in the regulation of human corpus cavernosum smooth muscle contractility by nitric oxide

1 This study was designed to determine the role of sodium‐potassium adenosine triphosphatase (Na+‐K+‐ATPase) in the regulation of human corpus cavernosum smooth muscle contractility by nitric oxide (NO). In addition, we determined if the modulation of Na+‐K+‐ATPase activity by NO is dependent on the increases in intracellular cyclic GMP concentration. 2 The effect of NO donors, sodium‐nitroprusside (SNP) and S‐nitroso‐glutathione (S‐NO‐Glu), and a permeable cyclic GMP analogue, 8‐bromo‐cyclic GMP, on Na+‐K+‐ATPase activity (measured as ouabain‐sensitive 86Rb‐uptake) was studied in human cultured corpus cavernosum smooth muscle cells (HCCSMC). In addition, the effect of the cyclic GMP lowering agent, methylene blue, on NO‐induced increase in Na+‐K+‐ATPase activity was studied. 3 SNP (1 μm) caused time‐dependent increases in ouabain‐sensitive Rb‐uptake (33–72%) over 2–20 min in HCCSMC. The stimulation of ouabain‐sensitive Rb‐uptake by SNP was concentration‐dependent (30 and 102% with 0.1 and 1 μm SNP, respectively). Similarly, significant increases in ouabain‐sensitive Rb‐uptake were obtained with 1 and 10 μm S‐NO‐Glu. In contrast, incubation of HCCSMC with 8‐bromo‐cyclic GMP (100 μm) did not increase ouabain‐sensitive Rb‐uptake. 4 S‐NO‐Glu induced‐increase in intracellular cyclic GMP synthesis, but not the increase in ouabain‐sensitive Rb‐uptake, was completely inhibited by methylene blue in HCCSMC. 5 The Na+‐K+‐ATPase inhibitor, ouabain, caused a concentration‐dependent increase in tension (0.5 to 2 fold) in tissues contracted with 15 mM KCL. SNP and S‐NO‐Glu caused a concentration‐dependent relaxation (concentration required to cause half maximal relaxation (ED50) = 0.04 and 0.2 μm, respectively) of HCC strips contracted with 15 mM K+. Ouabain (0.1 to 10 μm) inhibited the response to SNP and S‐NO‐Glu by shifting the concentration‐response curves to the right and preventing full smooth muscle relaxation. 6 These results indicate that the activity of Na+‐K+‐ATPase modulates the contractility of HCC smooth muscle, and that NO stimulates Na+‐K+‐ATPase activity in HCCSMC independently of its ability to increase the intracellular cyclic GMP concentration. They also suggest that stimulation of Na+‐K+‐ATPase activity plays an important role in NO‐induced relaxation of HCC smooth muscle