PubMed · 15487075
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Sindhu R Johnson, Catharine Dewar. 2004. Erectile dysfunction and scleroderma.. https://pubmed.ncbi.nlm.nih.gov/15487075/
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Treatment with alpha(1)-adrenergic receptor blockers improves lower urinary tract symptoms (LUTS) secondary to benign prostatic hyperplasia. This study was conducted to test the hypothesis that induction of apoptosis in prostate tissue could be a mechanism underlying the observed clinical benefit. This placebo-controlled, double-blind, randomized trial enrolled 536 men with LUTS who were treated with alfuzosin (10 or 15 mg) once daily or placebo for 3 months. Total prostate and transition zone volume was measured by standardized transrectal ultrasound measurements at baseline and 3 months. Total prostate volume increased by 0.4 ml from baseline in placebo patients but decreased by -0.25 ml in the combined alfuzosin groups. Percentage change was not statistically significantly different between the placebo and alfuzosin groups. Changes in transition zone volumes from baseline were similar in both treatment arms; percentage change was not statistically significantly different between the placebo and alfuzosin groups. Volume changes did not correlate with prostate volumes at baseline. Overall, neither total prostate nor transition zone volume increased or decreased systematically within the 3-month treatment period. If alfuzosin-induced apoptosis in prostate tissue, it was not evident by a measurable change in prostate volume after 3 months' treatment. Further analysis at 1 and 2 years will determine the effect of longer-term treatment.
AIM: To determine if tamsulosin treatment prevents or decreases the incidence and severity of outlet obstruction-induced bladder dysfunction in rabbits. MATERIALS AND METHODS: Male New Zealand White rabbits were treated with tamsulosin or vehicle for 4 weeks with treatments initiated 1 week prior to sham or obstruction surgery. Cystometry was done on anesthetized rabbits 21 days after surgery. The bladders were then removed, weighed, and prepared for in vitro whole bladder studies. Responses to 32 Hz field stimulation (FS), carbachol, phenylephrine, and KCl were measured. RESULTS: Obstruction resulted in a significant increase in bladder weight, which was unchanged by tamsulosin treatment and a significant increase in micturition pressure in the vehicle-treated group but not in the tamsulosin-treated group. Compliance was significantly decreased in both obstructed groups. The vehicle-treated obstructed rabbits had a very sharp increase in intravesical pressure as the bladder reached capacity; this was not seen in the tamsulosin-treated obstructed rabbits. Tamsulosin did not change the pattern of modifications in contractile responses induced by bladder outlet obstruction. CONCLUSIONS: In vitro responses of vehicle and tamsulosin-treated obstructed rabbit groups in this study were similar. A greater micturition pressure was found for the vehicle-treated obstructed group than for the tamsulosin-treated obstructed group, which was probably due to decreased urethral resistance in the latter. On a functional basis, the higher compliance at capacity and decreased micturition pressure in the tamsulosin-treated obstructed group would be considered beneficial for bladder function.
G protein-activated inwardly rectifying K+ channels (GIRK, also known as Kir3) are regulated by various G-protein-coupled receptors. Activation of GIRK channels plays an important role in reducing neuronal excitability in most brain regions and the heart rate. Ifenprodil, which is a clinically used cerebral vasodilator, interacts with several receptors, such as alpha1 adrenergic, N-methyl-D-aspartate, serotonin and sigma receptors. However, the molecular mechanisms underlying the various clinically related effects of ifenprodil remain to be clarified. Here, we examined the effects of ifenprodil on GIRK channels by using Xenopus oocyte expression assays. In oocytes injected with mRNAs for GIRK1/GIRK2, GIRK2 or GIRK1/GIRK4 subunits, ifenprodil reversibly reduced inward currents through the basal GIRK activity. The inhibition was concentration-dependent, but voltage- and time-independent, suggesting that ifenprodil may not act as an open channel blocker of the channels. In contrast, Kir1.1 and Kir2.1 channels in other Kir channel subfamilies were insensitive to ifenprodil. Furthermore, GIRK current responses activated by the cloned kappa-opioid receptor were similarly inhibited by ifenprodil. The inhibitory effects of ifenprodil were not observed when ifenprodil was applied intracellularly, and were not affected by extracellular pH, which changed the proportion of the uncharged to protonated ifenprodil, suggesting its action from the extracellular side. The GIRK currents induced by ethanol were also attenuated in the presence of ifenprodil. Our results suggest that direct inhibition of GIRK channels by ifenprodil, at submicromolar concentrations or more, may contribute to some of its therapeutic effects and adverse side effects.