zaprinast and trequinsin

Pharmacologic treatments are gaining widespread acceptance as first-line therapy for anal fissure. However, existing treatments have limited clinical usefulness because of side effects and incomplete healing rates.. Fresh human surgical resection specimens containing internal anal sphincter and rectal circular muscle were collected. Strips of smooth muscle were cut from each muscle group and mounted in a superfusion organ bath. The effects of increasing concentrations of phosphodiesterase inhibitors were evaluated.. All phosphodiesterase inhibitors tested caused a dose-dependent reduction in the tone of the internal anal sphincter, with potencies as follows: vinpocentine (phosphodiesterase-1 inhibitor; 50 percent maximum inhibition concentration = 0.87 +/- 0.10 microM), erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (phosphodiesterase-2 inhibitor; 32 +/- 4.8 microM), trequinsin (phosphodiesterase-3 inhibitor; 0.28 +/- 0.041 microM), rolipram (phosphodiesterase-4 inhibitor; 63 +/- 9 microM), zaprinast (phosphodiesterase-1,5,6,9,11 inhibitor; 3 +/- 0.69 microM), and dipyridamole (phosphodiesterase-5,6,8,10,11 inhibitor; 5.5 +/- 2 microM). Although all inhibitors were also effective on rectal circular muscle strips, erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride, trequinsin, and rolipram were at least an order of magnitude more potent in this tissue than in the internal anal sphincter.. There are several functionally important phosphodiesterases in the internal anal sphincter and rectal circular muscle. Both adenosine 3', 5'-cyclic monophosphate and guanosine 3',5'-cyclic monophosphate appear to be important in the myogenic tone of the internal anal sphincter, and this study provides further evidence of the sphincteric specialization of this tissue. Phosphodiesterase inhibitors might represent a new therapy for the treatment of anal fissure.

Topics: Adenine; Aged; Aged, 80 and over; Anal Canal; Dipyridamole; Dose-Response Relationship, Drug; Female; Humans; In Vitro Techniques; Isoquinolines; Male; Middle Aged; Muscle Relaxation; Muscle, Smooth; Phosphodiesterase Inhibitors; Platelet Aggregation Inhibitors; Purinones; Rectum; Rolipram; Tetrahydroisoquinolines; Vinca Alkaloids

Cellular export of cyclic nucleotides has been observed in various tissues and may represent an elimination pathway for these signaling molecules, in addition to degradation by phosphodiesterases. In the present study we provide evidence that this export is mediated by the multidrug resistance protein isoform MRP5 (gene symbol ABCC5). The transport function of MRP5 was studied in V79 hamster lung fibroblasts transfected with a human MRP5 cDNA. An MRP5-specific antibody detected an overexpression of the glycoprotein of 185 +/- 15 kDa in membranes from MRP5-transfected cells and a low basal expression of hamster Mrp5 in control membranes. ATP-dependent transport of 3',5'-cyclic GMP at a substrate concentration of 1 micrometer was 4-fold higher in membrane vesicles from MRP5-transfected cells than in control membranes. This transport was saturable with a K(m) value of 2.1 micrometer. MRP5-mediated transport was also detected for 3',5'-cyclic AMP at a lower affinity, with a K(m) value of 379 micrometer. A potent inhibition of MRP5-mediated transport was observed by several compounds, known as phosphodiesterase modulators, including trequinsin, with a K(i) of 240 nm, and sildenafil, with a K(i) value of 267 nm. Thus, cyclic nucleotides are physiological substrates for MRP5; moreover, MRP5 may represent a novel pharmacological target for the enhancement of tissue levels of cGMP.

Topics: Adenosine Triphosphate; ATP-Binding Cassette Transporters; Biological Transport; Cloning, Molecular; Cyclic AMP; Cyclic GMP; Glucuronates; Glutathione; Humans; Isoquinolines; Multidrug Resistance-Associated Proteins; Nucleotides, Cyclic; Phosphodiesterase Inhibitors; Piperazines; Purines; Recombinant Proteins; Sildenafil Citrate; Substrate Specificity; Sulfones; Tetrahydroisoquinolines

Phosphodiesterases (PDE) are key enzymes regulating intracellular cyclic nucleotide turnover and, thus, smooth muscle tension. Recent reports have indicated the presence of PDE isoenzymes 1, 2, 4, and 5 in cytosolic supernatants prepared from human ureteral smooth muscle homogenates and the ability of second-generation inhibitors of PDE 3, 4, and 5 to relax KCl-induced tension of human ureteral muscle in vitro. The aim of the present study was to evaluate the functional effects of recently developed, third-generation isoenzyme-selective PDE inhibitors, the nitric oxide (NO)-donating agents sodium nitroprusside (SNP) and dihydropyridine (DHP), which is also described as an antagonist of L-type calcium channels, and the adenylyl cyclase-stimulating drug forskolin on tissue tension and cyclic nucleotide levels of human ureteral smooth muscle segments in vitro. Relaxant responses of human ureteral smooth muscle were investigated in vitro using the organ bath technique. Cyclic nucleotides cAMP and cGMP were determined by specific radioimmunoassay following time and dose-dependent incubation of the ureteral tissue with the drugs. The most pronounced relaxing effects on KCl-induced tension of ureteral smooth muscle were exerted by nitrovasodilator SNP, PDE4 inhibitor rolipram, and PDE5 inhibitors E 4021 and morpholinosulfonyl-pyrazolopyrimidine (MSPP). Relaxing potency of the drugs was paralleled by their ability to elevate intracellular levels of cGMP and cAMP, respectively. Our data suggest the possibility of using selective inhibitors of PDE isoenzymes 4 and 5 in the treatment of ureteral stones and ureteral colic.

Topics: Colforsin; Cyclic AMP; Cyclic GMP; Humans; In Vitro Techniques; Isoquinolines; Muscle, Smooth; Nitroprusside; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperidines; Platelet Aggregation Inhibitors; Potassium Chloride; Purinones; Quinazolines; Rolipram; Tetrahydroisoquinolines; Ureter; Vasodilator Agents

The effects of family selective inhibitors of phosphodiesterase (PDEI, PDE2, PDE3, PDE4, and PDE5) on the behavior of rats under either a differential-reinforcement-of-low-rate (DRL) 72-s schedule or a variable-interval (VI) 30-s schedule were determined; previous work has shown that antidepressant drugs increase reinforcement rate under long DRL schedules. The PDE4-selective inhibitor rolipram (0.03-0.1 mg/kg) reduced response rate and increased reinforcement rate under the DRL schedule in a dose-dependent manner; similar effects were observed with the tricyclic antidepressant drug desipramine (3-10 mg/kg). Both of these drugs produced biphasic effects on behavior maintained under the VI schedule, increasing response rate at the lower doses tested (rolipram: 0.003 mg/kg; desipramine: 0.03 mg/kg) and decreasing response rate at higher doses (rolipram: 0.1 mg/kg; desipramine: 0.3-18 mg/kg). Of the other PDE inhibitors tested, only the PDE5-selective inhibitor zaprinast (10 mg/kg) produced an antidepressant-like effect on DRL behavior. However, in contrast to the biphasic effects of rolipram and desipramine on VI behavior, zaprinast produced monotonic decreases in response rate (10-30 mg/kg). The PDE2-selective inhibitor trequinsin produced biphasic effects on response rate under the VI schedule, increasing rates at low doses (3-5.6 mg/kg) and decreasing rates at higher doses (18-30 mg/kg). Trequinsin also reduced response rate under the DRL schedule (30 mg/kg); however, the reduction in response rate was not accompanied by increased reinforcement rate. The PDE3-selective inhibitor milrinone (1-10 mg/kg) tended to increase response rates under both schedules while the PDE1-selective inhibitor vinpocetine did not affect behavior at the dose range tested (1-30 mg/kg). These findings suggest that inhibition of PDE4 results in a rather unique pattern of behavioral effects, most notably an antidepressant-like effect on DRL behavior. It remains to be determined if a similar effect produced by zaprinast also implicates PDE5 in the mediation of antidepressant activity or represents an effect of this drug on PDE4 activity at high doses.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Antidepressive Agents, Tricyclic; Conditioning, Operant; Cyclic Nucleotide Phosphodiesterases, Type 1; Desipramine; Isoquinolines; Male; Milrinone; Phosphodiesterase Inhibitors; Purinones; Pyrrolidinones; Rats; Rats, Sprague-Dawley; Reinforcement Schedule; Rolipram; Tetrahydroisoquinolines; Vinca Alkaloids

Two cyclic nucleotide phosphodiesterase (PDE) activities were identified in pig aortic endothelial cells, a cyclic GMP-stimulated PDE and a cyclic AMP PDE. Cyclic GMP-stimulated PDE had Km values of 367 microM for cyclic AMP and 24 microM for cyclic GMP, and low concentrations (1 microM) of cyclic GMP increased the affinity of the enzyme for cyclic AMP (Km = 13 microM) without changing the Vmax. This isoenzyme was inhibited by trequinsin [IC50 (concn. giving 50% inhibition of substrate hydrolysis) = 0.6 microM for cyclic AMP hydrolysis in the presence of cyclic GMP; IC50 = 0.6 microM for cyclic GMP hydrolysis] and dipyridamole (IC50 = 5 microM for cyclic AMP hydrolysis in the presence of cyclic GMP; IC50 = 3 microM for cyclic GMP hydrolysis). Cyclic AMP PDE exhibited a Km of 2 microM for cyclic AMP and did not hydrolyse cyclic GMP. This activity was inhibited by trequinsin (IC50 = 0.2 microM), dipyridamole (IC50 = 6 microM) and, selectively, by rolipram (IC50 = 3 microM). Inhibitors of cyclic GMP PDE (M&B 22948) and of low Km (Type III) cyclic AMP PDE (SK&F 94120) only weakly inhibited the two endothelial PDEs. Incubation of intact cells with trequinsin and dipyridamole induced large increases in cyclic GMP, which were completely blocked by LY-83583. Rolipram, SK&F 94120 and M&B 22948 did not significantly influence cyclic GMP accumulation. Dipyridamole enhanced the increase in cyclic GMP induced by sodium nitroprusside. Cyclic AMP accumulation was stimulated by dipyridamole and trequinsin with and without forskolin. Rolipram, although without effect alone, increased cyclic AMP in the presence of forskolin, whereas M&B 22948 and SK&F 94120 had no effects on resting or forskolin-stimulated levels. These results suggest that cyclic GMP-stimulated PDE regulates cyclic GMP levels and that both endothelial PDE isoenzymes contribute to the control of cyclic AMP.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Aorta; Calcium; Cells, Cultured; Chromatography, Ion Exchange; Colforsin; Cyclic AMP; Cyclic GMP; Dipyridamole; Endothelium, Vascular; Isoquinolines; Kinetics; Purinones; Pyrazines; Pyrrolidinones; Rolipram; Swine; Tetrahydroisoquinolines