Faculty Bibliography

We have recently utilized radioligand receptor binding methods to characterize muscarinic cholinergic and alpha adrenergic receptors in human prostate adenomas. The primary advantages of radioligand receptor binding methods are that neurotransmitter receptor density is quantitated, the affinity of unlabelled drugs for receptor sites is determined, and receptors can be localized using autoradiography on slide-mounted tissue sections. Recently, [125I]-Heat, a selective and high affinity ligand with high specific activity (2200 Ci/mmole) has been used to characterize alpha 1 adrenergic receptors in the brain. In this study alpha 1 adrenergic receptors in the dog prostate were characterized using [125I]-Heat. The Scatchard plots were linear indicating homogeneity of [125I]-Heat binding sites. The mean alpha 1 adrenergic receptor density determined from these Scatchard plots was 0.61 +/- 0.07 fmol/mg. wet wt. +/- S.E.M. The binding of [125I]-Heat to canine prostate alpha 1 adrenergic binding sites was of high affinity (Kd = 86 +/- 19 pM). Steady state conditions were reached following an incubation interval of 30 minutes and specific binding and tissue concentration were linear within the range of tissue concentrations assayed. The specificity of [125I]-Heat for alpha 1 adrenergic binding sites was confirmed by competitive displacement assays using unlabelled clonidine and prazosin. Retrospective analysis of the saturation experiments demonstrated that Bmax can be accurately calculated by determining specific [125I]-Heat binding at a single ligand concentration. [125I]-Heat is an ideal ligand for studying alpha 1 adrenergic receptors in the prostate and its favorable properties should facilitate the autoradiographic localization of alpha 1 adrenergic receptors in the prostate

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

The sympathetic innervation of human prostate adenomas has been previously demonstrated using fluorescence microscopy and in vitro isometric studies. A clinical implication of these observations is that bladder outlet obstruction in men with benign prostatic hypertrophy may be subject to pharmacologic manipulation using adrenergic drugs. Randomized clinical trials have demonstrated the efficacy of alpha adrenergic antagonists for symptomatic BPH. We have previously characterized the alpha1 and alpha2 adrenergic receptors in the human prostate using [3H]prazosin and [3H]rauwolscine, respectively. The mean alpha1 and alpha2 receptor densities in the adenomas studied were equivalent. The effect of alpha2 adrenergic drugs on prostatic urethral pressure has not been examined in the human or in an animal model. In this study a canine model was used to define the effect of alpha2 drugs on prostatic urethral pressure. Intravenous administration of clonidine, a selective alpha2 agonist, resulted in a dose dependent increase in prostatic urethral pressure. The maximal increase in urethral pressure ranged between 18 to 30 cm. H2O. The maximal response to clonidine was approximately 50% less than the response to epinephrine, indicating that clonidine acts as a partial agonist. Pretreatment with yohimbine, a selective alpha2 adrenergic antagonist, abolished the effects of clonidine and epinephrine. The alpha2 adrenergic receptors were then studied in the canine prostates using [3H]rauwolscine. The equilibrium dissociation constant, Kd, ranged between 0.68 to 1.80 nM and the receptor density ranged between 14.8 to 69.3 fmol./mg. protein. The receptor density was homogeneous in specimens obtained from the proximal, midportion, and distal canine prostate suggesting that the effect of alpha2 drugs is not sphincter mediated. These in vitro and in vivo studies provide the basis for investigating the effects of alpha2 antagonists in men with symptomatic BPH

[3H]Rauwolscine ([3H]Ra), a selective ligand for the alpha 2 adrenergic receptor, was used to identify and characterize alpha 2 adrenergic receptors in prostate glands of men with benign prostatic hyperplasia. Specific binding of [3H]Ra to prostatic tissue homogenates was rapid and readily reversible by addition of excess unlabelled phentolamine. Scatchard analysis of saturation experiments demonstrates a single, saturable class of high affinity binding sites (Bmax = 0.31 +/- 0.04 fmol./microgram. DNA, Kd = 0.9 +/- 0.11 nM.). The relative potency of alpha adrenergic drugs (clonidine, alpha-methylnorepinephrine and prazosin) in competing for [3H]Ra binding sites was consistent with the order predicted for an alpha 2 subtype. The role of alpha 2 adrenergic receptors in normal prostatic function and in men with bladder outlet obstruction secondary to BPH requires further investigation

The surgical management of classical bladder exstrophy (functional bladder closure or urinary diversion) should be influenced by the inherent detrusor function of the exstrophied bladder. Cystometrograms performed previously on individuals with successful exstrophy closures demonstrate normal bladder function. The biochemical and neurophysiological properties of the exstrophied bladder have otherwise not been investigated. In this study radioligand receptor binding techniques were used to compare the density and equilibrium dissociation constant of muscarinic cholinergic receptors in control and exstrophy bladders. The density of muscarinic cholinergic receptors in the control and exstrophy groups was 1.97 plus or minus 0.29 and 1.44 plus or minus 0.21 fmol. per microgram deoxyribonucleic acid (mean plus or minus standard error of mean), respectively. The dissociation constant of the control and exstrophy groups was 0.15 plus or minus 0.02 and 0.14 plus or minus 0.02 nM. (mean plus or minus standard error of mean), respectively. These data show that the muscarinic receptor density and binding affinity in control and exstrophy bladders are similar. Therefore, the neurophysiological composition of the exstrophied bladder is not grossly altered during the anomalous development

Prostatic secretion is dependent upon the integrity of the endocrine and autonomic nervous systems and is dramatically influenced by muscarinic cholinergic analogs. In this study, we have used radioligand receptor binding methods on whole tissue homogenates and slide mounted tissue sections of rat prostate to determine whether androgens regulate the density of muscarinic cholinergic receptors in the prostate. The muscarinic cholinergic receptor binding affinities (Kd) of [3H] N-methylscopolamine in prostatic homogenates obtained from intact, castrate, and castrate rats receiving testosterone replacement (castrate + T) were similar (0.07 to 0.10 nM). The muscarinic cholinergic receptor binding capacity decreased 73 per cent following castration. Testosterone administration restored the density of muscarinic cholinergic receptors in castrate rats to intact levels. In order to ensure that the loss of receptor density was not due to a decrease in the epithelial: stromal cell ratio, the number of muscarinic cholinergic receptors per unit area of epithelium was determined in the 3 treatment groups using autoradiography on slide mounted tissue sections. The density of muscarinic cholinergic receptors in a unit area of epithelium was decreased 91 per cent following castration. Testosterone administration restored the density of muscarinic cholinergic receptors in the castrate rats to intact levels. The modulation of neurotransmitter receptors by steroid hormones may be a mechanism by which sex steroids regulate biological responsiveness of target tissues

Bladder outlet obstruction in men with benign prostatic hyperplasia is decreased following administration of prazosin, a selective alpha1 adrenergic antagonist. Prazosin presumably binds and antagonizes alpha1 adrenergic receptors on the smooth muscle cells of the prostatic adenoma. This study represents the first identification and characterization of alpha1 adrenergic receptors in the prostate using radioligand receptor binding methods. The binding of [3H] prazosin in homogenates obtained from human prostatic adenomas was saturable and a single high affinity prazosin binding site was identified (Kd = 0.29 +/- 0.09 nM). The alpha1 adrenergic receptor concentration in these homogenates ranged between 0.28 to 2.05 fmol./ mg. wet wt. prostate. The equilibrium dissociation constant and density of prazosin binding sites were similar in different regions of an enucleated prostate suggesting homogeneity of receptor density and receptor binding sites within an adenoma. The receptor density was not directly proportional to the weight of the surgically removed adenoma. The pharmacology of the prazosin binding sites was characterized by competitive binding experiments using [3H] prazosin and several unlabelled adrenergic analogs. The IC50's determined from competitive binding experiments using [3H] prazosin and alpha-methylnorepinephrine, rauwolscine and corynanthine were characteristic of alpha1 adrenergic receptor binding

The inheritance pattern of the exstrophy-epispadias complex was investigated by a combined literature review and a survey of the personal experience of pediatric urologists in North and South America, and Europe. Bladder exstrophy recurred in only 9 of approximately 2,500 families (1 in 275) with bladder exstrophy or complete epispadias. The recurrence of the exstrophy-epispadias complex in offspring of parents with bladder exstrophy or complete epispadias has never been described previously. We identified 215 offspring produced by parents with bladder exstrophy or epispadias, and bladder exstrophy was inherited in 3 of the offspring (1 in 70 live births). The recurrence of bladder exstrophy in offspring of parents with the exstrophy-epispadias complex is greater than previously assumed

A total of 24 boys with classical bladder exstrophy underwent initial urethral reconstruction at our hospital between 1975 and 1982. Penile reconstruction in male patients with classical bladder exstrophy includes penile lengthening, release of the dorsal chordee and reconstruction of the urethra. The former 2 procedures are performed during the primary bladder closure and urethroplasty usually follows bladder neck reconstruction. A modified Young urethroplasty was done in 22 of the 24 patients. Preputial pedicle grafts of free full thickness skin grafts were used for urethroplasty in 2 boys with insufficient penile skin. Fistulas requiring surgical revision developed after urethroplasty in 21 per cent of the patients. A prior osteotomy was associated with a decreased fistula rate. The cosmetic and preliminary functional results of the penile reconstruction were assessed by parental interviews. The definitive assessment of the penile reconstruction will be determined when these boys reach sexual maturity