The ischemia induced vasospasm of the renal arterial blood vessels mediated by α1-adrenoceptors is of importance for the loss of kidney function. This is based on reduced perfusion of the kidney cortex occuring in kidney transplant and organ preserving surgery. The present study considered the intracellular mechanism of the norepinephrine (NE) induced renal artery vasospasm by using swine renal artery smooth muscle ring. Norepinephrine and phenylephrine (PE) induced dose-dependent and fully reversible isometric contractions with a threshold concentration of 10 nM (n=7) and 10 nM (n=4), and an EC50 of 0.3 μM and 1 μM, respectively. The receptor was identified as α1A-subtype. The contraction was completely inhibited by verapamil (IC50=1.51 μM; n=11) and diltiazem (IC50=9.49 μM; n=8) and 85% by nifedipine (IC50=0.13 μM; n=21). Blockade of the intracellular inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ store by thapsigargin (1 μM, n=7) or suppression of Ca2+ release from the intracellular Ca2+-sensitive Ca2+ store by ryanodine (100 μM, n=4) inhibited the PE induced contraction by 39.5% and 47.6%, respectively. The results suggest a key role of voltage-dependent Ca2+ channels and intracellular Ca2+ stores in the α1A-adrenoceptor induced contraction of the renal artery.

Introduction: Relaxation of cavernous smooth muscle cells is essential for the initation of penile erection, which is the therapeutical goal in the treatment of erectile dysfunction (ED). Cellular contractility is mainly regulated by changes in the free intracellular Ca2+-concentration [Ca2+] that is determined by the interactions of Ca2+-influx through voltage-dependent L-type Ca2+-channels, Ca2+-release from intracellular pools and Ca2+-extrusion systems. Hormones, neurotransmitters and other mediators may affect cellular contractility by modulating the activity of these cellular compartments via intracellular second messengers.Materials and Methods: The present study focuses on the intracellular mechanism of the alpha(1)-adrenoceptor induced cavernous smooth muscle contraction using the patch-cramp technique combined with the fura II fluorescence technique in enzymatically isolated human cavernous smooth muscle myocytes.Results: The selective alpha(1)-adrenoceptor agonist norepinephrine (NE) increased the free cytoplasmic Ca2+-concentration [Ca2+] by stimulation of phospholipase C (PLC) resulting in generation of IP3- which releases Ca2+ from IP3-sensitive Ca2+-stores leading to an increase of the transmembraneous Ca2+-current (I-Ca). Furthermore, experiments were designed to understand the intracellular pathways activated by prostaglandin E1 (PGE1), morpholino-syndnonimin hydrochloride (SIN 1) and calcitonin gene related peptide (cGRP) used in autoinjection therapy of ED, and to compare their efficiency in inducing cavernous smooth muscle relaxation on the cellular level. PGE1 > cGRP > SIN 1 lowered [Ca2+] dose-dependently by inhibition of I-Ca. The inhibition of I-Ca could he imitated by forskolin, a direct activator of adenylate cyclase, and by intracellular application of cAMP (50 mu M; 47.9 +/- 4.2%, n = 18), 8-Br-cAMP (50 mu M; 59.3 +/- 3.7%, n = 11), 8-CPT-cAMP (50 mu M; 64.1 +/- 54%, n = 14). However, intracellular administration of cGMP (50 mu M; 44.6 +/- 5.6%, n = 21) or extracellularly applied SIN 1 did not provoke additional inhibition of I-Ca when the cytoplasm was already enriched with cAMP. The selective inhibitor of the cGMP-inhibited phosphodiesterase III (PDE III) milrinon (1 mM, 39.2 +/- 7.0, n = 8) also reduced I-Ca, but the SIN 1 and milrinon induced I-Ca inhibitions were not additive. Moreover, the PGE1, cGRP, SIN 1 and cGMP evoked I-Ca inhibitions were completely suppressed by RpcAMPS (100 mu M, n = 11), a specific blocker of the cAMP-dependent protein kinase (PKA).Conclusions: The experimental results underline the importance of cytosolic cAMP concentration for cavernous smooth muscle relaxation. PGE1, cGRP and SIN 1 increase the cytosolic cAMP level, whereby PGE1 and cGRP stimulate adenylatecyclase and SIN 1 activates guanylatecyclase. A connection between the cAMP and cGMP pathways is provided by PDE III. The inhibition of I-Ca can be explained by a phosphorylation of cavernous smooth muscle L-type Ca2+-channels. Thus the up- and down-regulation of cavernous smooth muscle Ca2+-channels seems to be crucial for the regulation of cavernous smooth muscle tone. This knowledge is useful for the development of molecular strategies in the therapy of ED.

Objective: The aim of the present study was to evaluate the therapeutic potency of an electrotherapy of striated ischiocavernous muscles in patients with erectile dysfunction. Patients and Methods: Transcutaneous electrostimulation of striated ischiocavernous muscles by self-adhesive penile or perineal skin electrodes was performed in 48 patients with erectile dysfunction. 6/48 patients (R) responded to intracavernous pharmacotherapy while 42/48 (NR) did not show significant penile rigidity even to intracavernous papaverine/phentolamine/PGE1 triple drug medication. Results: Within the observation time of 3 months, 10/48 patients dropped out. 22/38 patients reported a penile rigidity for sufficient sexual intercourse whereby 3/22 NR required additional intracavernous pharmacotherapy. Penile rigidity could be objectivated by triple drug medicaton in 12/14 NR after ischiocavernous muscle stimulation (EIS) therapy. 5/6 R were treated successfully for premature erection loss. During EIS treatment neither discomfort nor complications could be observed. Conclusion: Transcutaneous electrostimulation of ischiocavernous muscles is a new, noninvasive therapy for the improvement of penile rigidity. The clinical results underline the importance of the striated ischiocavernous muscles for penile rigidity.

The dynamic infravesical obstruction occurring in BPH is based on a alpha(1A)-adrenoceptor mediated stimulation of prostatic smooth muscle contractility. The present study yields the cellular mechanism of alpha(1A)-adrenoceptor induced prostatic smooth muscle contraction and the selectivity and potency of various adrenoceptor blockers and cyclic nucleotides by using the patch-clamp technique in enzymatically isolated human prostatic myocytes. Phenylephrine (PE) stimulated the transmembranous L-type Ca2+-current from 7.8 mu A/cm(2) up to 18.2 mu A/cm(2) simultaneously increasing the free cytoplasmic Ca2+-concentration [Ca2+](i) up to 1.9 mu M. Intracellular application of inositol 1,4,5-trisphosphate (IP3) imitated while blockers of intracellular Ca2+-release suppressed the PE mediated response. Therefore intracellular Ca2+-liberation seems to be crucial for the dynamic obstruction in BPH. The alpha(1A)-induced stimulation of Ca2+-channel current was dose-dependently and reversibly suppressed by alfuzosin (IC50 0.39 +/- 0.11 nM) > tamsulosin (IC50 0.52 +/- 0.12 nM) > terazosin (IC50 1.85 +/- 0.32 nM) > doxazosin (IC50 2.40 +/- 0.30 nM). In renal artery smooth muscle tissue the following ICS, were determined: terazosin (34.5 +/- 0.6 nM) > tamsulosin (46.7 +/- 3.5 nM) doxazosin (121.8 +/- 5.4 nM) > alfuzosin (212 +/- 7.2 nM) leading to selectivity-scores (renal artery-IC50/prostate-IC50) of alfuzosin (543.59) tamsulosin (89.81) doxazosin (50.75) terazosin (18.65). The cyclic nucleotides cAMP and cCMP inhibited the PE contraction up to 85%. The knowledge of cellular signal transduction enables the development of innovative therapy strategies.

Purpose: A variant form of anterior hypospadias, called a megameatus and intact prepuce (MIP), is thought to be less amenable to conventional distal hypospadias repair. The feasibil

The presynaptic release of norepinephrine leads to a rise in cytosolic Ca2+ and promotes contraction of the cavernous smooth muscle. Ca2+ derives from the extracellular space and sarcoplasmic stores. The importance of intracellular stores was investigated in an organ bath study using tissue strips of rabbit cavernous muscle, Contractions were induced by phenylephrine and electrical stimulation. After incubation in Ca2+-free solution as well as after administration of nifedipine till contractile responses were encountered. Ryanodine, a functional blocker of intracellular Ca2+-channels, significantly inhibited contractions and caffeine pronounced this effect. Rabbit cavernous smooth muscle contraction seems to involve an influx of Ca2+-ions from the extracelluar space and sarcoplasmic Ca2+-stores.

The role of signal transducing guanine-nucleotide binding proteins (G-proteins) in α1-receptor mediated smooth muscle contractions was investigated in human hyperplastic prostatic tissue. The selective α1-receptor agonist phenylephrine (PE) evoked dose dependent contractions antagonized by the α1-receptor blockers prazosin (EC50 10 nM) and YM 617 (EC50 3 nM). Application of nifedipine (1–10,000 nM), a blocker of voltage-dependentl-type Ca2--channels (VDCC), inhibited the PE evoked contraction up to 65.4%. Pretreating the tissue strips with pertussis toxin (PTX, exotoxin from Bordetella pertussis; 5–25 μg/ml), inactivating a subpopulation of G-proteins, inhibited the PE induced contractions up to 73.9%. PTX pretreatment had no effect on contractions elicited by 125 mMK-. Application of nifedipine to PTX pretreated tissue led to an additional inhibition of 13.7%. Our findings demonstrate the involvement of PTX-sensitive G-proteins in the signal transduction pathway of α1-receptor induced contractions of prostatic smooth muscle. The remaining contractility of PTX pretreated tissue suggests additional participation of PTX insensitive mechanisms in α1-receptor mediated prostatic smooth muscle contractions.

Guinea pig vas deferens was used as an animal model for alpha-1 adrenoceptor (α1-receptor) mediated contractions in human hyperplastic prostatic tissue. The selective α1-receptor agonist, phenylephrine (PE), induced fully reversible, dose-dependent contractions antagonized by increasing concentrations of the α1-receptor blockers prazosin (1–100 nM) and YM 617 (0.1–10 nM). Removal of extracellular Ca2+ reduced PE-evoked contractions in a time-dependent manner. Nifedipine (1–1000 nM), a blocker of voltage-dependent L-type Ca2+ channels (VDCC), inhibited the PE-induced response by up to 65%. Removal of extracellular Ca2+ abolished the α1-agonist reactivity in a time-dependent fashion. To elucidate the participation of intracellular Ca2+ stores in α1-receptor contractions, the tissue was pretreated with ryanodine (10 μM) or thapsigargin (0.1 μM), established inhibitors of Ca2+ release from intracellular pools. Both substances reduced the PE contractions by up to 80%. Nifedipine suppressed the remaining contractions completely. This provides evidence that Ca2+ influx through VDCC and Ca2+ release from intracellular stores contribute to α1-receptor contractions in the guinea pig vas deferens and may be important in obstructive benign prostatic hyperplasia.