Receptor for motilin identified in the human gastrointestinal system.

Motilin is a 22-amino acid peptide hormone expressed throughout the gastrointestinal (GI) tract of humans and other species. It affects gastric motility by stimulating interdigestive antrum and duodenal contractions. A heterotrimeric guanosine triphosphate-binding protein (G protein)-coupled receptor for motilin was isolated from human stomach, and its amino acid sequence was found to be 52 percent identical to the human receptor for growth hormone secretagogues. The macrolide antibiotic erythromycin also interacted with the cloned motilin receptor, providing a molecular basis for its effects on the human GI tract. The motilin receptor is expressed in enteric neurons of the human duodenum and colon. Development of motilin receptor agonists and antagonists may be useful in the treatment of multiple disorders of GI motility.

Distinct mechanism for antidepressant activity by blockade of central substance P receptors.

The localization of substance P in brain regions that coordinate stress responses and receive convergent monoaminergic innervation suggested that substance P antagonists might have psychotherapeutic properties. Like clinically used antidepressant and anxiolytic drugs, substance P antagonists suppressed isolation-induced vocalizations in guinea pigs. In a placebo-controlled trial in patients with moderate to severe major depression, robust antidepressant effects of the substance P antagonist MK-869 were consistently observed. In preclinical studies, substance P antagonists did not interact with monoamine systems in the manner seen with established antidepressant drugs. These findings suggest that substance P may play an important role in psychiatric disorders.

Endogenous insulin-like growth factor (IGF) binding proteins cause IGF-1 resistance in cultured fibroblasts from a patient with short stature.

The ED50 of insulin-like growth factor (IGF)-I-stimulated alpha-aminoisobutyric acid (AIB) uptake (mean +/- SD) in cultured fibroblasts from a child with short stature that we have reported (1.40 +/- 0.24 nM), is significantly higher than the ED50 of IGF-I-stimulated AIB uptake in fibroblasts from 11 normal subjects (0.42 +/- 0.12 nM) and from 127 short children (0.35 +/- 0.11 nM). Similarly, the ED50 of IGF-I-stimulated thymidine incorporation in fibroblasts from this child is 2.8 times higher than that in fibroblasts from four normal subjects. To minimize potential modulation of IGF-I action by endogenous IGF binding proteins in these assays, fibroblast responsiveness to [Q3,A4,Y15,L16]IGF-I, an IGF-I variant that has a 600-fold reduced affinity for serum IGF binding proteins, has been examined. The biological activity of this variant is comparable in the patient's and normal fibroblasts, suggesting that the resistance to IGF-I action cannot be attributed to a defective IGF-I receptor. To investigate directly the possibility that IGF-I sensitivity in the patient's fibroblasts is reduced by endogenous IGF binding proteins (IGFBP), binding proteins that are secreted into AIB assay buffer during a 3-h collection and that are cell-associated at the end of the collection have been analyzed. Ligand blot analysis of conditioned AIB assay buffer demonstrates that fibroblasts from the patient secrete 1.3-2.2 times more of Mr 46,400/42,900, 32,000, and 26,800 binding proteins than normal fibroblasts. The major difference between fibroblasts from the patient and from normal subjects is a striking 10-fold increase in the amount of a cell surface Mr 32,000 binding protein in the patient's fibroblasts. The Mr 32,000 binding protein is similar in size to IGFB-1 and different from IGFBP-2 and IGFBP-3, but it does not cross-react with an antibody against IGFBP-1. We conclude that the resistance to IGF-I action in the patient's fibroblasts is caused by an abnormal production and/or cell association of IGF binding proteins.

A selective human beta3 adrenergic receptor agonist increases metabolic rate in rhesus monkeys.

Activation of beta3 adrenergic receptors on the surface of adipocytes leads to increases in intracellular cAMP and stimulation of lipolysis. In brown adipose tissue, this serves to up-regulate and activate the mitochondrial uncoupling protein 1, which mediates a proton conductance pathway that uncouples oxidative phosphorylation, leading to a net increase in energy expenditure. While chronic treatment with beta3 agonists in nonprimate species leads to uncoupling protein 1 up-regulation and weight loss, the relevance of this mechanism to energy metabolism in primates, which have much lower levels of brown adipose tissue, has been questioned. With the discovery of L-755,507, a potent and selective partial agonist for both human and rhesus beta3 receptors, we now demonstrate that acute exposure of rhesus monkeys to a beta3 agonist elicits lipolysis and metabolic rate elevation, and that chronic exposure increases uncoupling protein 1 expression in rhesus brown adipose tissue. These data suggest a role for beta3 agonists in the treatment of human obesity.

(Thr-59)-insulin-like growth factor I stimulates 2-deoxyglucose transport in BC3H1 myocytes through the insulin-like growth factor receptor, not the insulin receptor.

The murine non-fusing muscle cell line contains distinct receptors for insulin and insulin-like growth factors. Pretreatment of myocytes with insulin for 20 h at 37 degrees C inhibits the binding of [125I]iodoinsulin by 60% without affecting the binding of [125I]iodoinsulin-like growth factor I. The ED50 values for down-regulation of the insulin and insulin-like growth factor receptor by their respective ligands are 1 nM and 3 nM, respectively. Insulin, (Thr-59)-insulin-like growth factor I and multiplication-stimulating activity stimulate 2-[3H]deoxyglucose transport in myocytes with ED50 values of 5 nM, 5.6 nM and 33 nM, respectively. In order to determine whether (Thr-59)-insulin-like growth factor I stimulates 2-[3H]deoxyglucose transport in myocytes via its own receptor or the insulin receptor, we determined the activity of these peptides after down-regulation of the insulin receptor. The rate of 2-[3H]deoxyglucose transport in myocytes pretreated with insulin (5 nM) is elevated but returns to control levels by 1 h after the washout of insulin. The dose-response curve for insulin-stimulated 2-[3H]deoxyglucose transport is shifted to the right (ED50 greater than 100 nM) immediately after insulin washout but is normal by 1 h after insulin washout. In contrast, the dose-response curve for (Thr-59)-insulin-like growth factor I is unchanged in insulin-pretreated cells immediately after insulin washout. These data show that (Thr-59)-insulin-like growth factor I stimulates 2-[3H]deoxyglucose transport in myocytes by acting through an insulin-like growth factor receptor and not through the insulin receptor. Since multiplication-stimulating activity is 6-fold less active than (Thr-59)-insulin-like growth factor, they both may be acting through a type 1 insulin-like growth factor receptor.

The chemokine/chemokine-receptor family: potential and progress for therapeutic intervention.

The chemokines are a large superfamily of chemotactic cytokines that are utilized to direct the trafficking and migration of leukocytes within the immune system. The chemokines mediate their activity through a large family of G-protein-coupled receptors, and thus are highly tractable as therapeutic targets. Exciting advances have been made in the field within the past year, not the least of which is the disclosure of potent antagonists of several chemokine receptors. Several CCR5 antagonists have demonstrated potent antiviral activity and may represent novel therapeutic agents for the treatment of AIDS. In addition, new biological insights have been gained from the demonstration that the targeting of cells to inflammatory sites is tissue specific, such that different chemokine/chemokine-receptor pairs are utilized in recruitment of T-lymphocytes to the skin and to the intestine. Also, utilization of neutralizing antibodies to the CXCR3 ligand Mig in murine allograft transplantation models has demonstrated the importance of CXCR3 in orchestrating T-cell-mediated tissue rejection.

Species differences in prostatic steroid 5 alpha-reductases of rat, dog, and human.

The conversion of testosterone to 5 alpha-dihydrotestosterone by prostate particulates from rats, dogs, and humans was investigated, and significant species differences were found with their pH profiles, affinities for 4-azasteroidal inhibitors, and sensitivities to mercuric sulfhydryl reagents. The pH optima for the rat (pH 7), the dog (pH 6), and the human (pH 5) enzyme are significantly different. Mersalyl acid and p-hydroxymercuribenzoate inactivate only the rat 5 alpha-reductase, but not the human or dog enzyme. The rank orders of potencies of 24 3-oxo-4-azasteroids to inhibit 5 alpha-reductases of the rat, dog, and human prostate are different. The variation of the 17 beta-functional groups of the inhibitors demonstrates clearly the species differences. Those inhibitors with a 17 beta-diethylcarbamoyl, 17 beta-diisopropylcarbamoyl, 17 beta-t-butylcarbamoyl, or 17 beta-secbutylcarbonyl functional group are approximately equipotent as inhibitors of the rat and human enzymes, whereas they are only 0.1-15% as potent as inhibitors of the dog enzyme. On the other hand, those inhibitors with a 17 beta-spiroether functional group are most potent as inhibitors of the rat enzyme, are 15-50% as potent as inhibitors of the dog enzyme, and are 0.2-0.4% as potent as inhibitors of the human enzyme. Those inhibitors with a 17 beta-n-octylcarbamoyl, 17 beta-(1-carboxyethyl), or 17 beta-(1-carboxy-3-butyl) functional group are 2-3 orders of magnitude less potent as inhibitors of the dog and human enzymes than as inhibitors of the rat enzyme. These results suggest that prostatic 5 alpha-reductases of rats, dogs, and humans are significantly different. In spite of the significant species differences in inhibitor affinities, where determined, inhibition of the rat, dog and human enzymes by these compounds is competitive with testosterone. These 3-oxo-4-azasteroids have a similar rank order of potency as inhibitors of 5 alpha-reductase in human normal, benign hyperplastic, and cancerous prostates, indicating that the inhibitor-binding sites of 5 alpha-reductase in the prostate in different pathological states are similar. The affinities of the 3-oxo-4-azasteroids for rat prostatic cytosol receptor were determined. Five of these 5 alpha-reductase inhibitors have no significant affinity for the androgen receptor, whereas others do have an affinity for the receptor.

Competition for binding to insulin-like growth factor (IGF) binding protein-2, 3, 4, and 5 by the IGFs and IGF analogs.

The insulin-like growth factors (IGF) I and II bind to IGF binding proteins (BP) with high affinity. The affinity of each of the IGFs for individual BPs and the regions of the IGF-I molecule that are required for this high affinity binding have been defined only for IGFBP-1 and IGFBP-3. The present studies have determined the affinity of several IGF analogs (prepared using in vitro mutagenesis) for pure IGFBP-2, 3, 4, and 5. The results show IGFBP-2 binds these analogs in a manner similar to IGFBP-1. For example, a mutation in the A chain region (positions 49, 50, 51) or B chain (positions 3, 4) results in greater than 20-fold reduction in affinity for either IGFBP-1 or 2. In contrast, mutations in the A chain region have minimal effect on binding to IGFBP-3, whereas substitutions at the 3, 4, 15, 16 positions of the B chain reduce IGF-I affinity by at least 50-fold. At pH 7.4, binding of the analogs to IGFBP-4 is less affected by substitutions at the B chain 3, 4 positions compared to IGFBP-1, 2, and 3, but IGFBP-4 affinity for analogs containing the A chain substitutions is greatly reduced similarly to IGFBP-1 and 2. Binding to IGFBP-5 is greatly reduced by either A or B chain substitutions and most of the mutations result in greater than 100-fold reduction in affinity. Acidic pH 6.0 was associated with increased affinity of IGFBP-4 for the A chain containing mutants. The results indicate that only IGFBP-1 and 2 have nearly identical affinity for each of these analogs, whereas IGFBP-3, 4, and 5 have similarities and significant differences. The findings suggest that different binding proteins have differential structural requirements for optimal IGF-I binding.

Isolation of a preadipocyte cell line from rat bone marrow and differentiation to adipocytes.

A unique population of rat adipocyte precursor cells was derived from normal rat bone marrow. The epitheloid-like preadipocytes were isolated from a mixed culture of bone marrow cells by a combination of differential trypsinization, enrichment by Ficoll gradient centrifugation, and differential seeding. This cell line, designated RBM-Ad, can be fully differentiated into multilocular adipocytes morphologically resembling brown adipose tissue. No changes in the differentiation pattern are observed during propagation of these cells, and they have been successfully carried and differentiated up to passage 49. Histological staining of differentiated cells with Sudan black, Sudan IV, and oil red O indicates the presence of lipids in intracellular vesicles. The nonselective beta-adrenergic agonist isoproterenol stimulates adenylyl cyclase activity in both preadipocytes and differentiated adipocytes. In contrast, BRL-37344, a beta 3-adrenergic receptor-specific agonist, stimulates adenylyl cyclase activity and glycerol release in differentiated adipocytes, but not preadipocytes. In addition, differentiated adipocytes contain messenger RNA encoding the brown adipose-specific protein, thermogenin. Thus, this rat preadipocyte cell line can be differentiated into adipocytes that histologically and functionally resemble brown adipose tissue.

Serum half-life and biological activity of mutants of human insulin-like growth factor I which do not bind to serum binding proteins.

We have characterized the biological properties of two mutants of human insulin-like growth factor I (IGF-I) which, as we have shown previously, have normal affinity for the type I IGF receptor, but drastically reduced affinity for the acid-stable components of human serum binding proteins. [Phe-1,Val1,Asn2,Gln3,His4,Ser8,His9,Glu12 ,Tyr15,Leu16]IGF I (B-chain mutant) and [Gln3,Ala4,Tyr15,Leu16]IGF I have 1000 and 500 times lower affinity than IGF-I for the native 150K binding protein in adult rat serum. Like IGF-I, these two peptides migrate as monomers during size exclusion chromatography on TSK 125. [125I]IGF-I, [125I]B-chain mutant, and [125I] [Gln3,Ala4,Tyr15,Leu16]IGF-I have in vivo serum half-lives of 100, 27.5, and 26.9 min, respectively, after iv injection. These data suggest that serum binding protein-bound peptide is cleared from the serum more slowly than free peptide. The tissue distributions of [125I]IGF-I and [125I]B-chain mutant are similar 10 min after dosing, with more than 80% of the tissue-sequestered intact radioactive peptides in the kidney. Despite decreased serum half-lives, the B-chain mutant and [Gln3,Ala4,Tyr15,Leu16]IGF-I are, respectively, 4 times and twice as active as IGF-I in stimulating the incorporation of [14C]glucose into glycogen in rat diaphragm in vivo. This effect of IGF-I is thought to be mediated by the type 1 IGF receptor in muscle, since the same doses of peptide that stimulated glycogen synthesis more than 30-fold did not stimulate the incorporation of [14C]glucose into total lipid in adipose tissue, an effect known to be mediated by the insulin receptor. These data support the hypothesis that serum- or tissue-derived binding proteins impair the ability of IGF-I to exert its effects through the type 1 IGF receptor in vivo.

Inability of a mouse cell line transformed to produce biologically active recombinant human insulin-like growth factor I (IGF-I) to respond to exogenously added IGF-I.

A plasmid expression vector encoding human insulin-like growth factor I (hIGF-I) in the form of a 97-amino acid precursor protein containing the first 27 amino acids of prebovine GH and the 70 amino acids of hIGF-I has been used to transform mouse L cells. A stably transformed mouse L cell clone has been isolated which expresses and secretes hIGF-I. The secreted peptide comprises 3% of the protein in conditioned medium. IGF-I can be purified to homogeneity in 2 chromatographic steps. One liter of conditioned medium yields approximately 200 micrograms purified peptide. Amino-terminal sequence analysis confirms that the signal peptide has been proteolytically hydrolyzed from the precursor protein before secretion to form [Ala0]hIGF-I. The recombinant peptide and serum-derived hIGF-I are equipotent as inhibitors of the binding of [125I]IGF-I to the type 1 receptor of human placenta and to a crude preparation of acid-stable human serum binding proteins. The peptides are equipotent in 2 in vitro assays, the stimulation of the rate of 2-[1,2-N-3H]deoxyglucose transport in BC3H1 cells and the stimulation of [methyl-3-3H]thymidine incorporation into DNA in A10 cells. In contrast to a control mouse L cell line, DNA synthesis in the [Ala0]IGF-I-secreting line is completely unresponsive to [Thr59]IGF-I, while it responds normally to calf serum (10%). Thus, the [Ala0]IGF-I-secreting line is selectively desensitized to IGF-I. The binding of [125I]IGF-I to both lines is identical, indicating that the loss of responsiveness to IGF-I is not due to a loss of cell surface receptor. The ability to render mouse L cells unresponsive to IGF-I is transferred in the conditioned medium of the [Ala0]IGF-I-secreting cell line. In addition, pretreatment of control cells with [Thr59]IGF-I (10 nM) results in attenuation of the response to a subsequent dose of IGF-I. These data indicate that prolonged exposure to high levels of IGF-I may cause a postreceptor-mediated desensitization to IGF-I. Alternatively, IGF-I may promote secretion of an inhibitor of IGF-mediated DNA synthesis.

Identification of the insulin-like growth factor I (IGF I) epitopes recognized by monoclonal and polyclonal antibodies to IGF I.

We have characterized the binding epitopes of human insulin-like growth factor I (IGF I) for a polyclonal (UB286) and a monoclonal (SM 1.2) antibody using IGF analogs obtained by site-directed mutagenesis. The polyclonal antibody, UB286, which was obtained from the National Hormone and Pituitary Program, recognizes determinants surrounding residues 15 and 16 in the B-region and residues 49-51, 55 and 56 in the A-region. These residues are predicted to be within helical segments which are accessible for surface binding. The monoclonal antibody SM 1.2 selectively recognizes the region surrounding residues 15 and 16. Antibodies UB286 and SM 1.2 are both neutralizing antibodies as judged by their ability to inhibit binding of 125I-IGF I to type 1 receptors on human placental membranes. In addition, SM 1.2 inhibits the ability of IGF I and IGF analogs for which it has high affinity to stimulate DNA synthesis in murine fibroblasts. In contrast, analogs with substitutions at residues 15 and 16, which have poor affinity for SM 1.2, stimulate DNA synthesis with equal potency in the presence and absence of SM 1.2. These antibodies bind normally to analogs which we have previously shown have drastically reduced binding to type 1 IGF receptors, indicating that the antibodies and the receptors recognize distinct domains of IGF I.

Pharmacological characterization of a recently described human beta 3-adrenergic receptor mutant.

The beta 3-adrenergic receptor is the predominant subtype of beta-adrenergic receptor expressed in adipose tissue. Recently, a naturally occurring mutation in the human beta 3-receptor gene has been described which results in substitution of the tryptophan residue at position 64 in the first intracellular loop with an arginine residue. The polymorphism, which is prevalent in the human population, has been associated with increases in some parameters of obesity and Type II diabetes. In order to characterize the pharmacological effects of this amino acid substitution, the W64R mutation was made in the human beta 3 receptor gene and the resulting mutant receptor expressed in CHO cells. Activation by various agonists showed no significant differences (t-test, P > 0.05) between the wild type and mutant receptors. These studies show that, when expressed in a heterologous system, the W64R mutant receptor is pharmacologically and functionally indistinguishable from the wild type beta 3-adrenergic receptor.

Peroxisome proliferator-activated receptors gamma and alpha mediate in vivo regulation of uncoupling protein (UCP-1, UCP-2, UCP-3) gene expression.

A role for peroxisome proliferator-activated receptors, PPAR gamma and PPAR alpha, as regulators of energy homeostasis and lipid metabolism, has been suggested. Recently, three distinct uncoupling protein isoforms, UCP-1, UCP-2, and UCP-3, have also been identified and implicated as mediators of thermogenesis. Here, we examined whether in vivo PPAR gamma or PPAR alpha activation regulates the expression of all three UCP isoforms. Rats or lean and db/db mice were treated with PPAR gamma [thiazolidinedione (TZD)] or PPAR alpha (WY-14643) agonists, followed by measurement of messenger RNAs (mRNAs) for UCP-1, UCP-2, and UCP-3 in selected tissues where they are expressed. TZD treatment (AD 5075 at 5 mg/kg x day) of rats (14 days) increased brown adipose tissue (BAT) depot size and induced the expression of each UCP mRNA (3x control levels for UCP-1 and UCP-2, 2.5x control for UCP-3). In contrast, UCP-2 and UCP-3 mRNA levels were not affected in white adipose tissue or skeletal muscle. Chronic (30 days) low-dose (0.3 mg/kg x day) TZD treatment induced UCP-1 mRNA and protein in BAT (2.5x control). In contrast, chronic TZD treatment (30 mg/kg x day) suppressed UCP-1 mRNA (>80%) and protein (50%) expression in BAT. This was associated with further induction of UCP-2 expression (>10-fold) and an increase in the size of lipid vacuoles, a decrease in the number of lipid vacuoles in each adipocyte, and an increase in the size of the adipocytes. TZD treatment of db/db mice (BRL 49653 at 10 mg/kg x day for 10 days) also induced UCP-1 and UCP-3 (but not UCP-2) expression in BAT. PPAR alpha is present in BAT, as well as liver. Treatment of rats or db/db mice with WY-14643 did not affect expression of UCP-1, -2, or -3 in BAT. Hepatic UCP-2 mRNA was increased (4x control level) in db/db and lean mice, although this effect was not observed in rats. Thus, in vivo PPAR gamma activation can induce expression of UCP-1, -2, and -3 in BAT; whereas chronic-intense PPAR gamma activation may cause BAT to assume white adipose tissue-like phenotype with increased UCP-2 levels. PPAR alpha activation in mice is sufficient to induce liver UCP-2 expression.

Expression, purification and characterization of recombinant human insulin-like growth factor I in yeast.

Insulin-like growth factor I (IGF-I) is a 70 amino acid (aa) protein that is structurally similar and functionally related to insulin. We have inserted a synthetic gene coding for human IGF-I into a Saccharomyces cerevisiae expression vector utilizing the MF alpha 1 promoter and pre-pro leader peptide. This vector directs the expression and secretion of native, biologically active growth factor. Cleavage of the pre-pro alpha factor leader sequence in vivo results in the secretion of a 70-aa recombinant IGF-I molecule with the native N-terminal glycine residue. Human IGF-I purified from yeast culture supernatant is equipotent to serum-derived IGF-I in inhibiting [125I]IGF-I binding to type-I IGF receptors and crude human serum-binding proteins. Recombinant IGF-I is also equipotent to human IGF-I in the stimulation of DNA synthesis in rat aortic smooth-muscle cells. In contrast, yeast recombinant IGF-I is less potent than serum-derived IGF-I in binding to type-2 IGF receptors. The ability to produce native, biologically active IGF-I in yeast will allow the elucidation of binding domains through the expression and characterization of specific structural analogs.

Molecular cloning and characterization of a new receptor for galanin.

Galanin (GAL) is a widely distributed neuropeptide with diverse biological effects including modulation of hormone release, antinociception and modification of feeding behavior. Its effects are mediated through G-protein-coupled receptors (GPCR) for which only a single type has been cloned, GAL receptor 1 (GALR1). We describe the cloning of a second galanin receptor type, GALR2, from rat hypothalamus. The GALR2 amino acid sequence is 38% identical to GALR1 and is pharmacologically similar to GALR1 when expressed in COS-7 cells. GALR2 is encoded by a single gene containing at least one intron and expressed in a diverse range of tissues.

Structure-activity relationships of aminoalkyl and -aryl glycosides having insulin-like activity.

A number of alkyl, aryl, and aralkyl glycosides (mono- and disaccharides) substituted in the aglycon with a primary amino group have been found to exert insulin-like activity on rat adipocytes in vitro. Systematic variations in the saccharide configuration, glycosidic linkage, aglycon moiety, and sugar substitution pattern were investigated to delineate structure-activity relationships. A high degree of structural specificity was observed. Maximal insulin mimicking activity was obtained with the 6-aminohexyl 1-thio-D-mannopyranosides; the beta anomer was more active than the alpha anomer. Modification of the sugar hydroxyl groups resulted, in most cases, in partial or complete loss of biological activity at the levels tested; however, in a few instances, sugar-modified derivatives did show enhanced insulin-like effects. Specific structural types evaluated are discussed in greater detail. 6-Aminohexyl 1-thio-beta-D-mannopyramoside also exhibited in vivo insulin-like effects on both diaphragm muscle and omental adipose tissues. The specificities for the sugar as well as the aglycon portions of these carbohydrate derivatives suggest that both parts of the molecule are involved in the expression of the full biological activity observed; their respective roles in the mechanism of the insulin-like activity are discussed.

Synthesis and biological evaluation of NK1 antagonists derived from L-tryptophan.

The 3,5-bis(trifluoromethyl)benzyl ester of N-acetyl-L-tryptophan (3), which was derived from the screening lead N-ethyl-L-tryptophan benzyl ester, has been used as a starting point to identify high-affinity substance P receptor antagonists with improved in vivo activity. Altering the ester moiety to an amide or ether led to a substantial loss in binding affinity, but conversion to a ketone provided compounds with affinity comparable to the equivalent esters. A homochiral synthesis of the key intermediate amino ketone 15 was developed which allows its preparation on a large scale. From this intermediate a range of amine-containing acylamino derivatives were prepared with affinity optimized in the morpholinylbutyramide 161 which has an IC50 of 0.17 nM at the human NK1 receptor. In addition to improving affinity, the amino group also provided aqueous solubility for a number of these derivatives. When tested in vivo the quinuclidine derivative L-737,488 (16i) was found to be an orally active (ID50 = 1.8 mg/kg) inhibitor of substance P-induced dermal extravasation in the guinea pig.

Azasteroids: structure-activity relationships for inhibition of 5 alpha-reductase and of androgen receptor binding.

A series of steroids, primarily 4-azasteroids, were prepared and tested in vitro as inhibitors of human and rat prostatic 5 alpha-reductase and of binding of dihydrotestosterone to the rat androgen receptor. The primary structural modifications were changes of the A ring and of moieties attached at the C-17 position of the steroid nucleus. New A-ring modifications included the 4-cyano-3-oxo-delta 4 system in the carbocyclic series and 1 alpha-CN, 1 alpha-CH3, 1 alpha,2 alpha-CH2, 2 beta-F, 2-aza, 2-oxa, and A-homo changes in the 3-oxo-4-aza series. In addition, 4-azasteroids with a D-homo ring or methyl substitution at C-7 (alpha and beta) or C-16 (alpha and beta) were prepared. The majority of the C-17 substituents were prepared from reactive intermediates derived from the 17 beta-COOH. Enhanced 5 alpha-reductase inhibition in both the human and rat enzyme assays is seen with 4-CN substitution on 3-oxo-delta 4 steroids and with a C-17 side chain incorporating a lipophilically substituted semipolar group on the 4-aza-3-oxo-5 alpha-androstane nucleus. Fewer highly active compounds were found in the human enzyme assay than in the rat assay. Structural requirements for inhibition of the rat androgen receptor are much different from those for inhibition of the enzyme. The 17 beta-OH moiety enhances potency more than any other feature while introduction of double bonds at C-1 or C-5 in the azasteroid gives a small improvement. Azasteroids unsubstituted at the 4-position show greatly diminished receptor activity.

Identification of a series of 3-(benzyloxy)-1-azabicyclo[2.2.2]octane human NK1 antagonists.

The synthesis and in vitro and in vivo evaluation of a series of 3-(benzyloxy)-1-azabicyclo-[2.2.2]octane NK1 antagonists are described. While a number of 3,5-disubstituted benzyl ethers afford high affinity, the 3,5-bis(trifluoromethyl)benzyl was found to combine high in vitro affinity with good oral activity. Detailed structure-activity relationship studies in conjunction with data from molecular modeling and mutagenesis work have allowed the construction of a model of the pharmacophore. Specific interactions that have been identified include an interaction between His-197 and one of the rings of the benzhydryl, a lipophilic pocket containing His-265 that the benzyl ether occupies, and a possible hydrogen bond between Gln-165 and the oxygen of the benzyl ether.