Alpha 1 adrenergic receptors in canine lower genitourinary tissues: insight into development and function.
Radioligand receptor binding methods were used to characterize the alpha 1-adrenergic receptor in the bladder body, bladder base, prostate and urethra of the male dog. Saturation experiments were performed in tissue homogenates using [125iodine]-Heat, an alpha 1-adrenergic antagonist of high specific activity (2,200 Ci. per mmol.). The equilibrium dissociation constant Kd for [125iodine]-Heat binding in the bladder body (0.56 pM.), bladder base (0.81 +/- 0.11 pM.), prostate (0.86 +/- 0.19 pM.) and urethra (0.55 pM.) was similar, suggesting homogeneity of alpha 1-adrenergic binding sites in lower genitourinary tissues. The receptor density in the bladder body, bladder base, prostate and urethra, expressed as fmol. per mg. wet weight, was 0.22 +/- 0.02, 0.82 +/- 0.09, 0.55 +/- 0.06 and 0.27 +/- 0.06, respectively (mean +/- standard error of mean). Competitive binding experiments with [125iodine]-Heat and unlabeled prazosin and clonidine confirmed the selectivity of Heat for alpha 1-adrenergic binding sites. Anatomical dissections have revealed that a major component of the smooth muscle of the bladder base and prostate originates from the ureter, whereas a major component of the smooth muscle of the urethra originates from the bladder. The measured alpha 1-adrenergic receptor densities support these developmental theories.
Shapiro
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Division of Pediatric Urology, Children's Hospital of St. Louis, Missouri 63110.
Lepor
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D000818:Animals; D001667:Binding, Competitive; D004285:Dogs; D007457:Iodine Radioisotopes; D008297:Male; D010627:Phenethylamines; D011467:Prostate / Q000294:innervation; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D044024:Tetralones; D014521:Urethra / Q000294:innervation; D001743:Urinary Bladder / Q000294:innervation; D014566:Urogenital System / Q000294:innervation*
D007457:Iodine Radioisotopes; D010627:Phenethylamines; D011942:Receptors, Adrenergic, alpha; D044024:Tetralones; C010652:BE 2254