Pharmacokinetics of a series of 6-chloro-2,3,4,5-tetrahydro-3-substituted-1H- 3-benzazepines in rats. Determination of quantitative structure-pharmacokinetic relationships

To aid in the effort to discover novel agents for the treatment of cardiovascular disease, the relationships between pharmacokinetic parameters in the rat and lipophilicity and basicity were studied for a series of 6-chloro-2,3,4,5-tetrahydro-3-substituted-1H-3-benzazepines. Eight compounds, ranging in lipophilicity from log P = 1.64 to 3.50 and basicity from pKa = 6.75 to 9.36, were studied. The compounds were administered iv to rats, and the pharmacokinetic parameters were calculated from the plasma concentration-time curves. Plasma protein binding was determined in vitro using equilibrium dialysis to allow calculation of steady state volume of distribution of unbound drug, Vss,u; and tissue binding. Stepwise regression analysis with each pharmacokinetic parameter as the dependent variable and log P and pKa as the independent variables was performed. In no case was there a significant relationship between a pharmacokinetic parameter and both of the independent variables. Statistically significant linear relationships were found between pKa and Vss and t 1/2z. Lipophilicity was found to correlate with the free fraction in plasma and the free fraction in tissues. The clearance parameters did not correlate with either of the physicochemical parameters. The pharmacokinetics of the one secondary amine in the series were clearly different from those of any of the tertiary amines. The clearance of the secondary amine was lower and the volume of distribution higher than any of the tertiary amines. These results demonstrate that alteration of the lipophilicity of 3-substituted benzazepines does not alter their pharmacokinetics in a predictable fashion but that the pharmacokinetics of secondary amines may be substantially different than tertiary amines.

Pancreatic function testing in meconium disease in CF: two case reports

We report two infants with cystic fibrosis (CF), presenting with meconium ileus and meconium plug, who had no clinical or biochemical evidence of pancreatic insufficiency during infancy. They underwent pancreatic secretory function testing at 11 and 9 months of age, respectively. Both patients had sufficient lipase and colipase secretion to maintain normal digestion of fat, confirming that meconium disease in CF does not necessarily imply pancreatic insufficiency and the need for enzyme supplementation in infancy. Nonetheless, we documented markedly reduced enzyme secretion in both patients, implying a potential role for the pancreas in the pathogenesis of meconium disease, even when clinical pancreatic insufficiency is absent. In addition, our patient with meconium ileus had a severely limited fluid secretory capacity (10.3% of mean normal values). In contrast, the patient with the milder presentation of meconium plug had a far greater ability to secrete fluid (75% of mean normal), but had poorer pancreatic proteolytic activity. We suggest that impaired fluid secretion may be a very significant factor in the pathogenesis of meconium ileus, and we speculate that an inability to maintain sufficient intraluminal fluid relative to the degree of pancreatic proteolytic deficiency may more adequately explain the risk of occurrence and the severity of intestinal obstruction in CF than either factor alone.

Synthesis, conformation, and dopaminergic activity of 5,6-ethano-bridged derivatives of selective dopaminergic 3-benzazepines

To probe the suggestion that D-1 (DA1) dopamine receptors might possess an accessory pi-binding site in a location complementary to a suitably oriented aromatic ring (i.e., in an axial orientation approximately orthogonal to the catechol nucleus) in agonists such as 2,3,4,5-tetrahydro-1-phenyl-1H-3-benzazepine-7,8-diol (1) and 3',4'-dihydroxynomifensine (2) that are selective for this subtype, cis- and trans-2,3,4,8,9,9a-hexahydro-4-phenyl-1H-indeno[1,7-cd]azepine-6,7-diol were prepared. These compounds are 5,6-ethano-bridged derivatives of the D-1 selective dopamine receptor agonist 1. Introduction of the bridge reduces the conformational mobility of the parent molecule. Comprehensive conformational analyses by molecular mechanical methods indicated that both the cis and trans isomers could attain a conformation that places the phenyl substituent in an axial orientation. X-ray analysis of the trans isomer showed an axial disposition of the phenyl ring; however, NMR studies suggest that this conformation is fixed in the trans isomer, but not in the cis. The dopamine receptor binding affinity and intrinsic activity of the cis isomer were considerably greater than those of its trans counterpart; the cis isomer also demonstrated a high degree of selectivity for the D-1 subtypes. One possible explanation of these results, suggested by the molecular modeling studies, is that both the axial orientation of the phenyl postulated to be required for binding to the receptor and a putatively requisite location of the nitrogen in approximately the plane of the catechol ring can be attained only by the cis isomer in which the tetrahydroazepine ring is in a twist conformation. Conversely, these results might simply suggest a preference of the D-1 receptors for benzazepine agonists having the phenyl group in an equatorial orientation. Still another possibility is that the D-1 receptor binding site is in a sterically hindered area accessible only to compounds that are relatively planar. However, it requires an axial 1-phenylbenzazepine for strong binding. Thus, a conformationally flexible cis isomer could more readily achieve the different conformations required to both gain access to and bind with the D-1 site.

Multisubstrate inhibitors of dopamine beta-hydroxylase. 2. Structure-activity relationships at the phenethylamine binding site

1-Aralkylimidazole-2-thiones have been shown to be potent multisubstrate inhibitors of dopamine beta-hydroxylase (DBH; EC 1.14.17.1). In the present study, a series of 1-benzylimidazole-2-thiones was prepared to explore the effects of substitution in the benzyl ring on the inhibition of DBH. A detailed structure-activity relationship for in vitro activity was discovered and this was shown by a modified Hansch analysis to correlate (r = 0.91) with four key structural features of the benzyl ring: the presence of a hydroxyl at the 4-position, molar refractivity at the 3-, 4-, and 5-positions, inductive effects of the substituents at the 3-, 4-, and 5-positions, and pi-electron density. The affinity (Kis) of eight substituted inhibitors for DBH was shown to correlate (r = 0.75) with the affinity (KD) of comparably substituted tyramines for the ternary DBH-oxygen-tyramine complex. This correlate is used to support the hypothesis that binding of inhibitor to DBH occurs in a fashion that mimics the binding of tyramine substrates. The most potent inhibitors were selected for study in vivo in the spontaneously hypertensive rat model of hypertension. The changes in vascular dopamine and norepinephrine levels that resulted from oral administration of the inhibitors corresponded to the observed reduction in mean arterial blood pressure. A divergence between in vitro potency and in vivo efficacy upon oral dosing was noted and is suggested to result from an in vivo metabolic conjugation of the phenolic group of inhibitor.

Synthesis and dopaminergic binding of 2-aryldopamine analogues: phenethylamines, 3-benzazepines, and 9-(aminomethyl)fluorenes

A series of 2-aryldopamine analogues were synthesized and evaluated for their effects on D1 and D2 dopamine receptors. The 2-phenyldopamine and 6-phenylbenzazepine analogues exhibited weak binding to both D1 and D2 receptors. The 9-(aminomethyl)fluorenes also exhibited weak D2 binding; however, 2,5,6-trihydroxy-9H-fluorene-9-methanamine (4b) exhibited D1 binding comparable to apomorphine. The binding activity has been correlated with the calculated torsion angle of the biphenyl portion of these molecules. Good D1 dopamine binding occurs when the aromatic rings approach coplanarity; poor binding occurs when the aromatic rings are orthogonal.

Suspected villonodular synovitis in a dog

Progressive bilateral juxta-articular osteolytic lesions were detected in the coxofemoral joints of a dog. The differential diagnoses included neoplasia or an inflammatory process of periarticular tissue. The clinical signs, radiographic findings, and gross and microscopic appearance of the lesions were similar to the inflammatory changes of villonodular synovitis.

Peritonitis associated with vaginal leakage of dialysis fluid in continuous ambulatory peritoneal dialysis

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