Phosphodiesterase Isoenzymes in Human Ureteral Smooth Muscle: Identification, Characterization, and Functional Effects of Various Phosphodiesterase Inhibitors in vitro

Abstract

Phosphodiesterases (PDE) are key enzymes regulating intracellular cyclic nucleotide metabolism and, thus, contraction and relaxation of the muscle. At present, five different families of isoenzymes of PDE exist that show a distinct species-specific and organ-specific distribution. The aim of the present study was to analyze the PDE isoenzymes present in the human ureter and to evaluate the functional effects of isoenzyme-specific inhibitors in this tissue. Normal ureteral tissue was obtained during radical nephrectomies, homogenized, centrifuged, and the supernatant fraction was separated using DEAE-Sephacel anion-exchange chromatography. PDE assay was then performed and the isoenzymes characterized on the basis of their kinetic characteristics and their sensitivity to allosteric modulators and inhibitors. In vitro, longitudinal ureteral strips as well as ureteral rings were precontracted, and different selective and nonselective PDE inhibitors were added incrementally. Three different PDE isoenzymes were identified: PDE I (Ca/calmodulin-stimulated), PDE II (cyclic guanosine monophosphate-stimulated), and PDE IV (cyclic adenosine monophosphate-specific). All PDE inhibitors relaxed the strips dose-depen-dently with an EC50 of 30 µM for papaverine, 40 µM for zaprinast, 25 µM for quazinone, and 0.1 µM for rolipram. The existence of three different PDE isoenzymes was shown in this study. The ureter-relaxing effect of the PDE IV inhibitor at low concentrations, combined with its low effect on the systemic circulatory parameters, may open a possibility of using selective PDE IV inhibitors in the treatment of ureteral colics or ureteral stones.

Expression of Messenger Ribonucleic Acid Encoding for Phosphodiesterase Isoenzymes in Human Female Genital Tissues

“…Because of their central role in cellular signal transduction, PDE isoenzymes are considered important pharmacological targets and have therefore been isolated and characterized from various organs of the human genitourinary tract [11–14]. Up until now, 11 PDE isoenzymes have been described which are characterized by their kinetic properties, e.g., affinity for cyclic AMP and/or cyclic GMP, and sensitivity toward inhibitors and allosteric modulators of enzyme activity [15].…”

Physiology and Pharmacology of the Human Ureter: Basis for Current and Future Treatments

“…Cyclic nucleotide PDE influences smooth muscle tone by decreasing the level of cyclic nucleotides. PDE I, II and IV were recently identified in the human ureter and their inhibition were all shown to cause relaxation [91] . A ureter-relaxing effect of particularly PDE IV inhibitors might be useful in ureteric obstruction.…”

Evaluation of ureteric contraction: a comparison among ring, spiral‐cut and longitudinal segments

“…To study ureteric responses to inflammatory mediators and neurotransmitters, the sensitivity of the various methods of ureteric suspension must be determined. Traditionally, ureteric segments have been suspended as horizontal rings or longitudinal strips [2–7]. The musculature has been believed to be in a single layer, arranged in a tight helix, becoming more longitudinal as the ureter enters the bladder [8].…”