We investigated the binding characteristics of endothelin (ET) receptors in rabbit ureter, bladder dome, bladder base, and urethra and compared the observed receptor properties with those of cloned human ETA and ETB receptors expressed in Chinese hamster ovary K-1 (CHO) cells. Receptor binding experiments with [125I]ET-1 revealed the presence of a single class of specific, saturable, high affinity [125I]ET-1 binding sites in all of the regions of the studied urinary tract. The rank order of the densities (Bmax values) of [125I]ET-1 binding sites was: ureter "bladder dome > bladder base = urethra. ET-1 and ET-2 inhibited [125I]ET-1 binding to the membrane particulates from the various regions of the urinary tract with single high affinity constants. A selective ETA receptor antagonist, BQ 123, and selective ETB agonists, ET-3 and sarafotoxin S6c (STXc), inhibited [125I]ET-1 binding to bladder dome, bladder base, and urethra with high and low affinity constants indicating the presence of both ETA and ETB receptor subtypes in these tissues. The subtype specificity of ET receptors in the rabbit tissues is confirmed with inhibition data obtained from similar binding studies in cloned human ETA and ETB receptors. The proportions of high affinity binding sites for ET-3, representing ETB receptors, were approximately 25%, 27%, and 46% in bladder dome, bladder base, and urethra, respectively. Corresponding values for STXc were approximately 17%, 28%, and 43% in bladder dome, bladder base, and urethra, respectively. In contrast to the findings for ET-3 and STXc, the proportions of high affinity binding sites for BQ 123, representing ETA receptors, in bladder dome, bladder base, and urethra were approximately 84%, 74%, and 60%, respectively. In ureter, these selective compounds inhibited [125I]ET-1 binding with either a low (ET-3 and STXc) or a high binding affinity (BQ 123), suggesting the presence of only a single receptor subtype (ETA) in this tissue. These data indicate that there are regional differences in the density and subtype specificity of ET receptors in the rabbit urinary tract.

Previous studies from our laboratory demonstrated that 8 weeks after the induction of diabetes by the administration of streptozotocin (STZ) there was a downregulation of beta adrenergic and muscarinic cholinergic receptors in rat prostate, and that early insulin treatment (started 3 days after the onset of diabetes) prevented these alterations from occurring. In the present study, the effects of later insulin treatment (started 8 weeks after the onset of diabetes) on the reversibility of diabetes-induced alterations in beta adrenergic and muscarinic receptors in rat prostate were investigated. Three groups of rats were maintained for 16 weeks: 1) diabetics, 2) insulin-treated diabetics (subcutaneously injected with 5 to 8 U per day starting 8 weeks after the onset of diabetes) and 3) age matched controls. Binding studies with [3H]dihydroalprenolol (DHA) and [3H]quinuclidinyl benzilate (QNB) showed a significantly lower density of beta adrenergic and muscarinic cholinergic receptors in the diabetic rat prostate than in prostate from either controls or insulin-treated diabetic animals. Inhibition of [3H]DHA binding by isoproterenol, a beta adrenergic agonist, and binding of [3H]QNB by carbachol, a muscarinic agonist, indicated the presence of low and high affinity agonist binding sites for each receptor. The relative proportion of high affinity to total binding sites as well as the low and high affinity constants were similar in all groups. These data indicate that insulin treatment, begun 8 weeks after the onset of diabetes, can reverse the diabetes-induced downregulation of both beta adrenergic and muscarinic cholinergic receptors in STZ-diabetic rat prostates.

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Using the constant fusion and single injection technique the metabolic clearance rates (mean +/- SEM) for delta5-androstene-3beta, 17beta-diol (delta5-idol) were measured for 19 normal men (1311 +/- 67 1/24 h) and 10 normal women (858 +/- 63 1/24 h). The constant infusion technique yielded values for the conversation ratios for the transformation of delta5-diol to several products: dehydroepiandrosterone (DHEA)/delta5-diol of 0.06+/-0.01 for men and 0.05 +/- 0.01 for women, of delta5-diol sulfate/delta5-diol of 0.45 +/- 0.04 for men and 0.52 +/- 0.03 for women and of DHEA sulfate/delta5-diol of 5.53 +/- 0.26 for men and 5.02 +/- 0.42 for women. The single injection technique yielded rate constants (units) and volumes of distribution (liters) for delta5-diol; Ki = 34.3 +/- 4.3 for men and 35.0 +/- 3.9 for women, K2 = 63.7 +/- 4.1 for men and 75.1 +/- 4.2 for women, V1 = 23.1 +/- 3.2 for men and 11.9 +/- 2.3 for women, V2 = 14.8 +/- 3.7 for men and 9.2 +/- 3.2 for women. The mean delta5-diol plasma concentration was 1.08 +/- 0.10 ng/ml for 12 men and 1.17 +/- 0.16 ng/ml for 9 women. (he calculated blood production rates for delta5-diol were 1357 +/- 117 mug/24 h for 12 men and 969 +/- 131 mug/24 h for 9 women. The per cent binding (equilibrium dialysis) was higher for women (94.9 +/- 0.3) than for men (93.0 +/- 0.2). Paper electrophoresis showed that significant fractions of 3H-delta5-diol migrated with both the beta-globulin and albumin fractions. Estrogen administration to two normal men increased the per cent binding of delta5-diol to plasma proteins and decreased the metabolic clearance rate towards the values found for normal women.