Localization of an ataxia-telangiectasia gene to an approximately 500-kb interval on chromosome 11q23.1: linkage analysis of 176 families by an international consortium

We describe a 20-point linkage analysis map of chromosome 11q22-23 that is based on genotyping 249 families (59 CEPH and 190 A-T). Monte Carlo linkage analyses of 176 ataxia-telangiectasia (A-T) families localizes the major A-T locus to the region between S1819(A4) and S1818(A2). When seven nonlinking families were excluded from subsequent analyses, a 2-lod support interval of approximately 500 kb was identified between S1819(A4) and S1294. No recombinants were observed between A-T and markers S384, B7, S535, or S1294. Only 17 of the international consortium families have been assigned to complementation groups. The available evidence favors either a cluster of A-T genes on chromosome 11 or intragenic defects in a single gene.

Steroid hormone receptor status defines the MMTV promoter chromatin structure in vivo

The ability to respond to small signalling molecules such as steroid hormones is important for many physiological processes. Steroid hormones act through a group of high affinity receptors that regulate transcription by binding to hormone response elements (HREs) located within the promoters of target genes, which themselves are organized with nuclear proteins to form chromatin. To dissect the mechanisms(s) of steroid hormone action we have used the steroid inducible mouse mammary tumor virus (MMTV) promoter as a model system. The MMTV promoter is assembled into a phased array of nucleosomes that are specifically positioned in rodent cells. Induction of transcription by glucocorticoids is accompanied by the appearance of a hypersensitive region in the proximal promoter which allows the hormone dependent assembly of a preinitiation complex including transcription factors such as nuclear factor 1 (NF1) and the octamer transcription factor (OTF). Surprisingly, when introduced by transient transfection, the progesterone receptor (PR) is unable to activate this promoter in vivo, a finding that may result from its inability to alter MMTV promoter chromatin. In an attempt to investigate the failure of the PR to activate the promoter, we have stably introduced the MMTV promoter into human T47D breast cancer cells that express high levels of the PR. In contrast to what has been observed previously in rodent cells, the MMTV templates resident in human breast cancer cells adopt a novel and constitutively open chromatin structure. The constitutively open chromatin structure is accompanied by the hormone independent loading of transcription factors including the PR and NF1. In T47D cells that stably express the glucocorticoid receptor, the MMTV promoter responds to glucocorticoids, but not progestins, and displays glucocorticoid induced restriction enzyme hypersensitivity and transcription factor loading. These findings suggest that the organization of the MMTV chromatin structure is dependent upon the cell type and receptor status of the recipient cell into which the MMTV promoter is stably introduced.

Genetic haplotyping of ataxia-telangiectasia families localizes the major gene to an approximately 850 kb region on chromosome 11q23.1

The genotyping data given localize the major A-T gene to an approximately 850 kb region. They also localize the group A A-T gene (ATA) to a region that contains the approximately 850 kb region. They are compatible with linking A-TFresno to 11q22-23. NBS-V2 does not link to this region. Four non-linking families contain only single affecteds, suggesting that these may be spontaneous mutations rather than evidence for an A-T gene outside the 11q22-23 region. Finally, two other non-linking families contain recombinant haplotypes that are compatible with a second A-T gene at 11q22-23, slightly distal to the approximately 850 kb region. However, convincing evidence for a second gene is still lacking.

Genetic haplotyping of ataxia-telangiectasia families localizes the major gene to an approximately 850 kb region on chromosome 11q23.1

The genotyping data given localize the major A-T gene to an approximately 850 kb region. They also localize the group A A-T gene (ATA) to a region that contains the approximately 850 kb region. They are compatible with linking A-TFresno to 11q22-23. NBS-V2 does not link to this region. Four non-linking families contain only single affecteds, suggesting that these may be spontaneous mutations rather than evidence for an A-T gene outside the 11q22-23 region. Finally, two other non-linking families contain recombinant haplotypes that are compatible with a second A-T gene at 11q22-23, slightly distal to the approximately 850 kb region. However, convincing evidence for a second gene is still lacking.

Immunocytochemical localization of androgen receptors in human skin using monoclonal antibodies against the androgen receptor

Androgen receptors were localized in cryostat sections of human skin using monoclonal antibodies to the human androgen receptor. Bound antibodies were detected using biotinylated rabbit anti-rat IgG, peroxidase-conjugated streptavidin, and diaminobenzidine as chromogen. In the neonatal foreskin, antibody to androgen receptor bound to keratinocytes in the epidermis and to fibroblasts and vascular endothelial cells in the dermis. Immunohistochemical staining was stronger in nuclei than in cytoplasm. This staining was specific, because there was no significant staining when antibody to the androgen receptor was replaced with IgG from nonimmunized rats or with buffer, or when antibody to androgen receptor was incubated, prior to immunostaining, with a trp E-human androgen-receptor fusion protein used as immunogen. Incubation of androgen receptor antibody with trp E alone did not affect staining. Androgen-receptor antibody also bound to keratinocytes, fibroblasts, and endothelial cells in skin from adult men and women. Skin from the scalp, nose, lip, back, and chest gave positive staining for androgen receptor. Antibody to androgen receptor also bound to the coil and ductal cells of eccrine glands, external root sheath of hair follicles, epithelium in the hair bulb, dermal papilla cells, and sebocytes. There was no significant binding to adipocytes, collagen, or stratum corneum. These results show that androgen receptor is present in cells that are known to be targets for androgens and also in cells in which the biologic effects of androgens are yet to be characterized.

Inhibition of steroid 5 alpha-reductase by specific aliphatic unsaturated fatty acids

Human or rat microsomal 5 alpha-reductase activity, as measured by enzymic conversion of testosterone into 5 alpha-dihydrotestosterone or by binding of a competitive inhibitor, [3H]17 beta-NN-diethulcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one ([3H]4-MA) to the reductase, is inhibited by low concentrations (less than 10 microM) of certain polyunsaturated fatty acids. The relative inhibitory potencies of unsaturated fatty acids are, in decreasing order: gamma-linolenic acid greater than cis-4,7,10,13,16,19-docosahexaenoic acid = cis-6,9,12,15-octatetraenoic acid = arachidonic acid = alpha-linolenic acid greater than linoleic acid greater than palmitoleic acid greater than oleic acid greater than myristoleic acid. Other unsaturated fatty acids such as undecylenic acid, erucic acid and nervonic acid, are inactive. The methyl esters and alcohol analogues of these compounds, glycerols, phospholipids, saturated fatty acids, retinoids and carotenes were inactive even at 0.2 mM. The results of the binding assay and the enzymic assay correlated well except for elaidic acid and linolelaidic acid, the trans isomers of oleic acid and linoleic acid respectively, which were much less active than their cis isomers in the binding assay but were as potent in the enzymic assay. gamma-Linolenic acid had no effect on the activities of two other rat liver microsomal enzymes: NADH:menadione reductase and glucuronosyl transferase. gamma-Linolenic acid, the most potent inhibitor tested, decreased the Vmax. and increased Km values of substrates, NADPH and testosterone, and promoted dissociation of [3H]4-MA from the microsomal reductase. gamma-Linolenic acid, but not the corresponding saturated fatty acid (stearic acid), inhibited the 5 alpha-reductase activity, but not the 17 beta-dehydrogenase activity, of human prostate cancer cells in culture. These results suggest that unsaturated fatty acids may play an important role in regulating androgen action in target cells.

Anti-5 alpha-reductase autoantibodies in the serum of patients with prostatic cancer

Human sera were tested for their ability to inhibit 5 alpha-reductase binding of a potent inhibitor of the enzyme. Thirty one of 227 serum samples from patients diagnosed or suspected of prostatic cancer had a significant inhibitory activity, whereas 128 serum samples from other patients were inactive. The majority of the inhibitory activity was in the IgG fraction purified by chromatography on a protein A-Sepharose affinity column and an anti-human IgG-agarose column. IgG fractions from non-inhibitory sera were inactive. Inhibitory IgG also inhibited the enzymatic activity of microsomal 5 alpha-reductase from liver, ventral prostate and preputial gland of rat, and liver, prostate, and facial skin of human. The inhibitory IgG had no effect on NADH-menadione reductase or 17 beta-hydroxysteroid dehydrogenase. These results suggest that 5 alpha-reductase autoantibodies are present in the blood of some prostatic cancer patients.

Activation of sexual behaviour in castrated rats: the role of oestradiol

Sexual behaviour was induced in castrated male rats with oestradiol-17 beta- or testosterone-filled constant-release implants. Testosterone-induced sexual behaviour was unaffected by treatment with the 5 alpha-reductase inhibitor 17 beta-N,N-diethylcarbamoyl-4-aza-5 alpha-androstan-3-one (4-MA; 16.7 mg/day) but treatment with the aromatization inhibitor 1,4,6-androstatriene-3,17-dione (ATD; 10 mg/day) prevented testosterone from inducing the behaviour. Sexual behaviour could be activated in castrated rats treated with testosterone plus ATD by treatment with 4-MA or with implants filled with a low dose of oestradiol. Lordosis behaviour induced in ovariectomized rats with testosterone-filled implants and progesterone was blocked by ATD treatment and could not be activated with 4-MA but oestradiol implants restored the display of lordosis in the testosterone plus ATD-treated females. 4-MA inhibited the in-vitro formation of [14C]5 alpha-dihydrotestosterone from [14C]testosterone by combined preoptic and hypothalamic tissue at all doses tested and a high dose of oestradiol exerted a similar effect. The results suggest that androgen aromatization is required for testosterone-activated female sexual behaviour but not for testosterone-activated male sexual behaviour. It is suggested that oestradiol normally acts to control the sexual behaviour of male rats by modifying neural androgen metabolism.

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.

A comparative autoradiographic study of the distributions of substance P and eledoisin binding sites in rat brain

The relative potencies of tachykinin peptide analogs competing for binding of [125I]Bolton Hunter-conjugated substance P ([125I]BH-SP) or [125I]Bolton Hunter-conjugated eledoisin ([125I]BH-ED) in slide-mounted rat brain sections are very different, indicating the presence of two distinct tachykinin binding sites. The structure-activity profiles resemble those described in peripheral bioassay studies in which two tachykinin receptors have been postulated. Autoradiography of the two iodinated ligands bound with selective and one-site in vitro incubation conditions shows two discrete and distinctly different distribution patterns in brain. Binding sites for [125I]BH-ED are densely distributed in the accessory olfactory bulb, intermediate layers of the cerebral neocortex, portions of the hippocampal CA fields, hypothalamic supraoptic and paraventricular nuclei, central portions of the interpeduncular nucleus, sphenoid nucleus, medial subdivision of the solitary tract complex, and the substantia gelatinosa of the spinal cord. Binding sites for [125I]BH-SP are present in many of these same structures, but the densities and distribution patterns are different. In addition, [125I]BH-SP binds in numerous structures not labeled by [125I]BH-ED. Neither pattern matches the locations of terminations of endogenous tachykinin pathways marked by immunohistochemistry. The results suggest that it would be inappropriate to name brain tachykinin receptors according to the endogenous ligand which binds with highest affinity.

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.

Photoaffinity labeling of steroid 5 alpha-reductase of rat liver and prostate microsomes

21-Diazo-4-methyl-4-aza-5 alpha-pregnane-3,20-dione (Diazo-MAPD) inhibits steroid 5 alpha-reductase in liver microsomes of female rats with a Ki value of 8.7 +/- 1.7 nM, and the inhibition is competitive with testosterone. It also inhibits the binding of a 5 alpha-reductase inhibitor, [3H] 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one ([3H]4-MA), to the enzyme in liver microsomes. The inhibition of 5 alpha-reductase activity and of inhibitor binding activity by diazo-MAPD becomes irreversible upon UV irradiation. [1,2-3H]Diazo-MAPD binds to a single high affinity site (Kd 8 nM, 125 pmol binding sites/mg of protein) in liver microsomes of female rats, and this binding requires NADPH. Without UV irradiation, this binding is reversible, and it becomes irreversible upon UV irradiation. Both the initial reversible binding and the subsequent irreversible conjugation after UV irradiation are inhibited by inhibitors (diazo-MAPD and 4-MA) and substrates (progesterone and testosterone) of 5 alpha-reductase, but they are not inhibited by 5 alpha-reduced steroids (5 alpha-dihydrotestosterone and 5 alpha-androstan-3 alpha, 17 beta-diol). NADPH stimulates the binding of [3H] diazo-MAPD to microsomes of male rat liver and prostate. UV irradiation also induces conjugation of [3H] diazo-MAPD to these microsomes. Photoaffinity labeled liver microsomes of female rats were solubilized and fractionated by high performance gel filtration. The radioactive conjugate eluted in one major peak at Mr 50,000.

Demonstration of two distinct tachykinin receptors in rat brain cortex

Eledoisin and substance P are members of a class of peptides termed tachykinins. They share a similar spectrum of biological activities but their relative potencies in various pharmacological assays differ. We have investigated whether there is more than one receptor for these tachykinins in rat brain cortex membranes. 125I-Bolton Hunter-conjugated eledoisin specifically binds to rat brain cortex membranes with high affinity. The binding is inhibited over 95% by unlabeled eledoisin (6.6 microM). Scatchard analysis of the binding of this ligand is curvilinear suggesting that there are two binding sites with KD values of 0.9 +/- 0.7 nM and 20 +/- 10 nM. We tested various analogs and fragments of substance P and eledoisin for their ability to inhibit the binding of 125I-Bolton Hunter-conjugated eledoisin and 125I-Bolton Hunter-conjugated substance P to these membranes. The following peptides are more potent as inhibitors of the 125I-Bolton Hunter-conjugated eledoisin binding site than of the 125I-Bolton Hunter-conjugated substance P binding site: nonradioactive Bolton Hunter-conjugated eledoisin (greater than 100-fold), eledoisin (12-fold), kassinin (22-fold), neuromedin K (greater than 58-fold), and pyroglutamyl substance P(6-11)hexapeptide (4-fold). In contrast, substance P (21-fold), physalaemin (8-fold), and substance P methyl ester (1200-fold) were more potent as inhibitors of 125I-Bolton Hunter-conjugated substance P binding. These results suggest that these two ligands may bind to distinct receptors. 125I-Bolton Hunter-conjugated substance P binds specifically to rat parotid cell receptors, but 125I-Bolton Hunter-conjugated eledoisin does not, indicating that parotid cells contain only one of the receptor subtypes. The cortex membrane binding of both ligands is stimulated by low concentrations of MnCl2 (ED50 = 0.05 mM) and is inhibited by guanylyl-5'-(beta, gamma-imido)diphosphate (IC50 = 0.5 microM).

Inhibition of luteinizing hormone (LH)-releasing hormone-induced secretion of LH in rat anterior pituitary cell culture by testosterone without conversion to 5 alpha-dihydrotestosterone

The role of 5 alpha-reduction of testosterone in the inhibition of LH secretion was investigated in rat anterior pituitary cell cultures. Pituitary cells were preincubated with testosterone or dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one) for 17 h and then with LHRH for an additional 4 h. Dihydrotestosterone was 6-fold more potent than testosterone in the inhibition of LHRH-induced LH release. Basal LH secretion was not affected by either androgen. The inhibition curves of testosterone and dihydrotestosterone were not shifted by the presence of the 5 alpha-reductase inhibitors 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (4-MA) and 17 beta-N,N-diisopropylcarbamoyl-4-aza-androstan-3-one (DIPA). Neither 4-MA nor DIPA alone had an effect on either basal or LHRH-induced LH release. When pituitary cells were incubated with [3H]testosterone for 17 h, the radioactivities were found to be unmetabolized testosterone (66.9 +/- 2.4%), dihydrotestosterone (13.3 +/- 0.5%), androstenedione (15.9 +/- 1.3%), 5 alpha-androstane-3,17-dione (2.8 +/- 0.3%), and 3 alpha (beta), 17 beta-androstanediol (less than 1%). In the presence of 4-MA or DIPA, 5 alpha-reduction of testosterone was completely inhibited; androstenedione was the only metabolite. Androstenedione was only 12% as potent as testosterone in the inhibition of LHRH stimulation of LH release, and conversion of [3H]androstenedione to testosterone and dihydrotestosterone did occur in these cells. When [3H]dihydrotestosterone was incubated with pituitary cells, the radioactivities were dihydrotestosterone (64.4 +/- 0%), 5 alpha-androstanedione (19.3 +/- 1%), 3 alpha (beta), 17 beta-androstanediol (7.7 +/- 1.7%), and unknown polar metabolites. 4-MA and DIPA had no effect on the metabolism of dihydrotestosterone. These results indicate that both testosterone and dihydrotestosterone inhibit LHRH-induced LH release and that this activity of testosterone does not depend on its 5 alpha-reduction.

Visualization of rat brain receptors for the neuropeptide, substance P

Biochemical analysis of the binding of [125I]Bolton-Hunter coupled substance P [( 125I]BH-SP) to slide-mounted sections of rat brain demonstrated that [125I]BH-SP labels a binding site with a structure-activity profile characteristic of a substance P receptor. Under optimized preincubation and incubation conditions, the locations of substance P (SP) receptors were visualized by film and emulsion autoradiography. Receptor densities were quantified by computer-assisted densitometry. SP receptors are widely but discretely distributed throughout sensory, limbic and cortical areas of rat brain, though several motor areas also possess SP receptors. No receptors were detected in the substantia nigra and interpeduncular nucleus, which are innervated by SPergic nerves; these regions of the brain may possess a low affinity SP receptor not detectable with this assay. Findings are discussed in the framework of an overall notion of the role of neuropeptides in the biochemistry of emotion.

Binding of [125I]Bolton Hunter conjugated eledoisin to rat brain cortex membranes--evidence for two classes of tachykinin receptors in the mammalian central nervous system

[125I]Bolton Hunter conjugated eledoisin was prepared and purified by ion-paired reverse phase chromatography. The ligand binds to rat brain cortex membranes, and the binding is inhibited over 95% by unlabeled eledoisin (6.6 microM). The binding site appears to be distinct from the [125I]Bolton Hunter conjugated substance P receptor based on the relative potencies of substance P, eledoisin, kassinin, physalaemin and [pGlu]substance P (6-11) hexapeptide to displace the binding of these two ligands.

Autoradiographic localization of a novel peptide binding site in rat brain using the substance P analog, eledoisin

Using slide mounted sections of rat brain sausage, we have characterized the binding of [125I]Bolton Hunter conjugated eledoisin and [125I]Bolton Hunter conjugated substance P. Structure activity studies suggest that the two radiolabeled peptides bind to different binding sites. Autoradiographic studies support this notion. Whereas [125I]BH-SP sparsely labels the interpeduncular nucleus and does not label the substantia nigra at all, [125I]BH-ED densely labels the former and sparsely labels the latter structure. Further, the cortical labeling patterns obtained with the two peptides are strikingly different. These data support the hypothesis that there exist two classes of tachykinin binding sites in rat nervous tissue.

Carboxyl-terminal tripeptidyl hydrolysis of substance P by purified rabbit lung angiotensin-converting enzyme and the potentiation of substance P activity in vivo by captopril and MK-422

The hydrolysis of substance P is catalyzed by purified rabbit lung angiotensin-converting enzyme (peptidyldipeptide hydrolase, EC 3.4.15.1). The kcat/Km for the reaction at 37 degrees is 3.3 +/- 0.3 X 10(3) M-1 sec-1, which is 60 times less than that which has been reported for the hydrolysis of angiotensin I. The initial site of hydrolysis is the antipenultimate peptide bond, which generates the tripeptide amide (Gly-Leu-Met-NH2). This hydrolysis is inhibited by the angiotensin-converting enzyme inhibitors captopril, MK-422, and EDTA, and is dependent on the concentration of chloride ion. Both captopril and MK-422 potentiate the substance P-induced stimulation of salivation in rats. Thus, angiotensin-converting enzyme may be one of the enzymes that degrade substance P in vivo.

4-Azasteroidal 5 alpha-reductase inhibitors without affinity for the androgen receptor

In efforts to develop potent 5 alpha-reductase inhibitors without affinity for the androgen receptor, synthetic 3-oxo-5 alpha-steroids were tested for their ability to inhibit 5 alpha-reductase, using [14C]testosterone as the substrate, and for their ability to inhibit the binding of [3H]5 alpha-dihydrotestosterone to the androgen receptor of rat prostate cytosol. 2',3' alpha-Tetrahydrofuran-2'-spiro-17-(5 alpha-androstan-3-one) is not an inhibitor of 5 alpha-reductase and has a high affinity for the androgen receptor; substitution of the -CH2- at the 4-position with N-H resulted in a good inhibitor of 5 alpha-reductase. The 4-N-CH3 derivative is even more active, whereas the N-CH2-CH3 derivative is inactive. These 4-aza derivatives have much lower affinity for the androgen receptor than the parent compound. The 4-N-H derivatives of several 3-oxo-5 alpha-steroids were found to be 20-100% as potent as their corresponding 4-N-CH3 analogs as inhibitors of 5 alpha-reductase, whereas their androgen receptor affinities were at least 40-fold lower than their 4-N-CH3 analogs. Their 5 beta-isomers did not inhibit either 5 alpha-reductase or the androgen receptor binding of [3H]5 alpha-dihydrotestosterone. Two of these 4-N-H steroids, 17 beta-N,N-diethylcarbamoyl-4-aza-5 alpha-androstan-3-one and 17 beta-N, N-diisopropylcarbamoyl-4-aza-5 alpha-androstan-3-one, are potent 5 alpha-reductase inhibitors with Ki values equal to 29.2 +/- 1.7 and 12.6 +/- 0.8 nM, respectively, but have little affinity for the androgen receptor. The inhibition of 5 alpha-reductase by both compounds is competitive with testosterone. When [3H]testosterone was incubated with minced rat prostate in the presence of either of these two 4-azasteroids, the nuclear concentration of 5 alpha-dihydrotestosterone decreased and that of testosterone increased. The total nuclear uptake of testosterone plus 5 alpha-dihydrotestosterone was not significantly affected. These 4-azasteroids should be useful for investigating the importance of 5 alpha-reductase in androgen action in vivo.

12. Androgens: Pharmacodynamics and antagonists. Biochemical and biological studies with 4-aza-steroidal 5 alpha-reductase inhibitors

A series of 4-aza-3-oxosteroids were found to be good inhibitors of steroid 5 alpha-reductase. Two of these compounds. 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (4-MA) and 4-methyl-4-aza-5 alpha-pregnan-3-one-20(s)-carboxylate, inhibit 5 alpha-reductase competitively with testosterone (T) with Ki values of 5 and 1.7 nM, respectively. These 5 alpha-reductase inhibitors also have an affinity to the androgen receptor which is orders of magnitude lower than that of 5 alpha-dihydrotestosterone (DHT), spironolactone and cyproterone acetate. 4-MA decreases the prostatic concentration of DHT and increases that of T in intact male rats and in castrates given T or its propionate derivative. 4-MA is a better inhibitor of T-induced growth than of DHT-induced growth of the prostate and seminal vesicles in castrated rats. It decreases the weight of the prostate and seminal vesicles in intact rats and that of the prostate in dogs. It has no significant antifertility activity in rats. In pregnant rats, 4-MA reduces the ano-genital distance of male fetuses. 4-MA has no significant androgenic, estrogenic, progestational, antiprogestational or antigonadotrophic activity.

Characterization of the substance P receptor in rat brain cortex membranes and the inhibition of radioligand binding by guanine nucleotides

Rat brain cortex membranes bind to a conjugate of substance P and 125I-labeled Bolton-Hunter reagent, and this binding can be inhibited by a low concentration of substance P (Kd = 1.2 +/- 0.4 X 10(-8) M). This binding is reversible and saturable (0.5 +/- 0.1 pmol of binding sites/mg of protein). Fragments of substance P as small as the carboxyl-terminal hexapeptide can inhibit the binding although their potency decreases with the decrease in the length of the peptides. The binding affinities of smaller peptides or peptides in which the carboxyl-terminal amide or amino acids are removed are drastically reduced. Biologically active analogs of substance P, physalaemin, eledoisin, substance P methyl ester, [D-Ala0]hepta(5-11)substance P, kassinin, and the eledoisin-related hexapeptide also can inhibit the binding. However, the binding is not inhibited by polypeptides structurally unrelated to substance P or by amine hormones/neurotransmitters. The binding affinities of biologically active peptides to rat brain cortex membranes are almost identical with their affinities for rat parotid cells which we previously determined. Furthermore, the recently described substance P antagonist, [D-Pro, D-Trp]substance P, inhibits the binding of the 125I-labeled substance P derivative to brain cortex membranes and to parotid cells equally well. These results suggest that the substance P receptors in the brain cortex and the parotid gland are similar. The brain cortex membrane binding of the 125I-labeled substance P derivative can be inhibited by micromolar concentrations of GTP, GDP, and their analogs. ITP and IDP were less active. Adenine and pyridine nucleotides were inactive.

Binding of a 4-methyl-4-aza-steroid to 5 alpha-reductase of rat liver and prostate microsomes

A tritium labeled 5 alpha-reductase inhibitor, [1,2-3H] 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one ([3H]4-MA), binds reversibly to a high affinity site (Kd, 6.5 nM) in liver microsomes from male rats. The binding requires a nicotinamide nucleotide coenzyme; NADH is at least 100 times less potent than NADPH, and NADP+, NAD+, flavin adenine dinucleotide, coenzyme A, and ADP are inactive. The relative potencies of 13 steroids as inhibitors of the binding of [3H]4-MA to liver microsomes correlate with their relative potencies as inhibitors of the conversion of [14C]testosterone to [14C]5 alpha-dihydrotestosterone by liver microsomes. Comparison of liver microsomes from mature female rats and microsomes from mature male rat liver, ventral prostate, spleen, kidney, and skeletal muscle shows that their NADPH-dependent [3H]4-MA binding capacities correlate with their levels of 5 alpha-reductase activity. These results suggest that [3H]4-MA binds specifically to 5 alpha-reductase in a NADPH-dependent manner. 5 alpha-Reductase was solubilized from liver microsomes with a detergent, Lubrol-WX, and the solubilized enzyme also binds [3H]4-MA. The relative potencies of 13 steroids as inhibitors of rat ventral prostate and liver 5 alpha-reductase are the same, strongly suggesting that the 5 alpha-reductases in the two tissues are the same.

Substance P receptor on parotid cell membranes

A conjugate (125I-BH-SP) between substance P and 125I-labeled Bolton-Hunter reagent binds reversibly to a single class of high affinity (Kd = 4 nM) binding sites on dispersed rat parotid cells. The total number of binding sites is 49 +/- 17 fmol/mg of protein. The binding affinity of 13 fragments and analogs of substance P correlates with their relative potency in stimulating salivation. The smallest fragment of substance P which exhibits significant binding affinity and saliva-stimulating activity is the COOH-terminal hexa(6-11)peptide. Structurally unrelated neurotransmitters and hormones do not affect the parotid cell binding of 125 I-BH-SP. 125I-BH-SP pre-bound to the cells was recovered mainly in the particulate fractions of the cell homogenate. The 125I-BH-SP binding activity of the parotid cells was inactivated by pretreatment of the cells with papain but not with ribonuclease A or deoxyribonuclease I. Our results suggest that 125I-BH-SP binds to a substance P receptor on parotid membranes and that the receptor, at least in part, may be a protein.

Inhibition of 5 alpha-reductase, receptor binding, and nuclear uptake of androgens in the prostate by a 4-methyl-4-aza-steroid

17 beta-N,N-Diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (DMAA) is a potent reversible inhibitor of 5 alpha-reductase. The inhibition by DMAA of the conversion of testosterone to 5 alpha-dihydrotestosterone by rat prostate 5 alpha-reductase is competitive with testosterone, the apparent Ki being 5 nM, and uncompetitive with NADPH, DMAA inhibited both membrane-bound and solubilized 5 alpha-reductase. DMAA has moderate affinity for the prostate cytosol androgen receptor: 3 X 10(-6) M gives 50% inhibition of the binding of 10(-9) M 5 alpha-[3H]dihydrotestosterone to this receptor. This affinity to the androgen receptor is 1,000-, 500-, 120-, and 40-fold lower than that of 5 alpha-dihydrotestosterone, testosterone, spironolactone, and cyproterone acetate, respectively, and 7-fold higher than that of cimetidine. After incubation of [3H]testosterone with minced prostate, more than 90% of the radioactivity extracted from the nuclei co-chromatographed with 5 alpha-dihydrotestosterone and the rest with testosterone. DMAA at low concentrations decreased the ratio of 5 alpha-dihydrotestosterone to testosterone in the nuclei without significantly reducing the total uptake. DMAA at high concentrations also reduced the total radioactivity in the nuclei. This differential effect may reflect a higher affinity of DMAA for 5 alpha-reductase than for the androgen receptor. When 5 alpha-[3H]dihydrotestosterone was used in the tissue incubations, all radioactivity extracted from nuclei co-chromatographed with 5 alpha-dihydrotestosterone, regardless of whether or not DMAA was present. This nuclear uptake of 5 alpha-dihydrotestosterone is inhibited only by high concentrations of DMAA. In a cell-free system, the nuclear uptake of 5 alpha-[3H]dihydrotestosterone prebound to the cytosol receptor was not inhibited by DMAA. These results suggest that DMAA may inhibit nuclear uptake of 5 alpha-dihydrotestosterone by inhibiting the receptor binding. Sucrose gradient centrifugation of the radioactive KCl nuclear extracts prepared from the tissue incubations showed that the nuclear [3H]testosterone-receptor complex has a greater rate of dissociation than does the nuclear 5 alpha-[3H]dihydrotestosterone-receptor complex. [3H]Testosterone prebound to the prostate cytosol receptor also dissociates faster than 5 alpha-[3H]dihydrotestosterone prebound to the cytosol receptor.

Substance P stimulation of amylase release by isolated parotid cells and inhibition of substance P induction of salivation by vasoactive peptides

Substance P stimulation of salivation in rats has been studied as has its in vitro enhancement of amylase release by isolated parotid cells. The extent of the stimulation on amylase release by isolated parotid cells was dependent upon the concentration of substance P, with the minimum effective concentration being 1 nM. The substance P effect was detectable within 1 min after incubation and lasted for at least 50 min. Substance P stimulation was demonstrable at 25--37 degrees C but not at 0 degrees C. Adrenocorticotropic hormone (ACTH), thyrotropin-releasing hormone (TRH), vasopressin and neurotensin had no effect on amylase release. These results suggest that substance P may act directly on the parotid cells. Examination of the salivary-stimulating activity of fragments of substance P showed that the C-terminal octapeptide and (pyroglutamyl)hexapeptide were active, although less potent than substance P, whereas its free acid, C-terminal tetra- and tri-peptides were inactive. Vasopressin, angiotensin II and neurotensin could inhibit substance P induced salivation, whereas TRH, ACTH and somatostatin had no effect. Amylase activity per unit volume of saliva was not changed by the injection of vasopressin, angiotensin II or neurotensin. These vasoactive peptides did not affect substance P stimulation of amylase release by isolated parotid cells. The results indicate that vasopressin, angiotensin II and neurotensin inhibit the action of substance P on salivation at sites other than the parotid cells.

Selective polyamine-binding proteins. Spermine binding by an androgen-sensitive phosphoprotein

Rat ventral prostate contains an acidic protein which can bind spermine selectively. The relative binding affinities of various aliphatic amines for the protein are, in decreasing order, spermine greater than thermine greater than greater than putrecine greater than 1,10-diaminodecane, cadaverine and 1,12-diaminododecane. The binding protein has an isoelectric point at pH 4.3 and a sedimentation coefficient of 3 S. Its molecular weight is approx. 30 000. Histones and nuclear chromatin preparations of the prostate can interact with the binding protein. The spermine-binding activity of the purified prostate protein can be inactivated by treatment with intestinal alkaline phosphatases. The phosphatase treated preparation can then be reactivated by beef heart protein kinase in the presence of cyclic AMP and ATP. The spermine-binding activity of the prostate cytosol protein fraction decreases after castration, but increases very rapidly after the castrated rats are injected with 5alpha-dihydrotestosterone. This finding raises the possibility that, in the postate, certain androgen actions may be dependent on the androgen-induced increase in the acidic protein binding of polyamines and their translocation to a functional cellular site such as nuclear chromatin. In the prostate cytosol, spermine also binds to 4-S tRNAs and to a unique RNA which has a sedimentation coefficient of 1.5 S.

Inhibition of P-enolpyruvate carboxykinase and of glyconeogenesis in Tetrahymena by 3-mercaptopicolinic acid

Tetrahymena grown overnight in deep cultures were incubated for 1 hr with [1-14C]labeled substrates in the presence or absence of 3-mercaptopicolinic acid (3MPA). 3-MPA inhibited appearance of label in glycogen from bicarbonate, acetate, pentanoate, octanoate, and succinate, but not from glycerol or glucose. In vitro assays of phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase activity showed that both enzymes were about equally distributed between the particulate and cytosol fractions. 3-MPA inhibited phosphoenolpyruvate carboxykinase from both the cytoplasmic and particulate fractions, but had no effect on phosphoenolpyruvate carboxylase from either location. These results suggest that the in vivo effects of this drug are due to inhibition of glyconeogenesis at this site.

Effect of 4-pentenoic acid on intermediate metabolism of Tetrahymena

The growth of Tetrahymena pyriformis strain HSM was strongly inhibited by 4-pentenoic acid. Supplementing the medium acetate reversed the growth inhibition, but pyruvate was ineffective. Glycogen content was much lower in cells grown with 4-pentenoic acid than in controls; this effect was not reversed by acetate or by pyruvate. There was little effect of 4-penteonic acid on the in incorporation of label from [1-14C]acetate, [2-14C]glycerol, [1-14C]ribose, [U-14C]fructose, or [1-14C]glucose into CO2 but incorporation of label into glycogen was inhibited, the strongest inhibition being on acetate and the weakest approximately 20%) on ribose, fructose, and glucose. A 3-compartment model for quantitation of labeled acetyl CoA fluxes was shown to be applicable to Tetrahymena grown in the presence of 4-pentenoic acid, and experiments were performed to establish the flux of [1-14C]acetyl CoA into glycogen, lipids, CO2, glutamate, and alanine. It was evident from the results of these experiments that 4-pentenoic acid did not appreciably inhibit beta-oxidation or lipogenesis, but markedly decreased the glyconeogenic flux of labeled acetyl-CoA from the peroxismal and outer mitochondrial compartments.

A quantitative analysis of metabolite fluxes along some of the pathways of intermediary metabolism in Tetrahymena pyriformis

A detailed model of intermediary metabolism has been constructed which is consistent with all known information on the compartmental structure of metabolism in Tetrahymena, on the enzyme complement of this cell, and on the localization of the enzymes. The model allows computation of the specific activity of every carbon atom of all metabolites and thus of the flux of carbon along the major pathways of metabolism under steady state conditions. To test the model, data were required from cells grown under standard conditions and then suspended in a dilute salt solution and incubated for 1 hour in a mixture of acetate, pyruvate, hexanoate, bicarbonate, and glutamate labeled in a total of 10 positions, but with only one substrate labeled in any given flask. Twenty-seven measurements of label incorporation into CO2, lipids, glycogen, glutamate, and alanine were made, plus measurements of label distribution into fatty acid and glycerol moieties for 4 of the substrates and of oxygen consumption and of glycogenolysis, yielding 33 independent measurements. These, plus about 18 "limit" measurements which also constrain any possible solutions, were in sufficient excess of the 23 independent parameters to permit a stringent assessment of the model. Equations derived directly from the structure of the model and from the known stereochemistry of the reactions were programmed on a PDP-15 computer and values of the Qo2 and of label expected to be incorporated into the various products actually measured were computed for any given set of flux rates. A set of flux rates was found which yielded an excellent fit to the observed data. The ability to achieve a fit to the data for an overdetermined system constitutes strong support for this structural model of intermediary metabolism and the computed flux rates therefore provide a quantitative description of metabolite flow in the intact cell. Despite the redundancy of measurements relative to parameters to be determined, it was not possible to define a unique set of values for the flux through phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase, although the relationship between these fluxes is specified by the model. The analysis allows estimation of the recycling of phosphoenopyruvate through pyruvate kinase under conditions of net glyconeogenesis and an apparently futile exchange of acetyl-CoA between the inner and outer mitochondrial compartments. Carbon flow through the glyoxylate bypass under these conditions is about one-third of that through the Krebs cycle. The analysis also shows a net transport of malate from the peroxisomes to the mitochondria, consistent with the anaplerotic role of the peroxisomal glyoxylate bypass in Tetrahymena.

A very rapid effect of androgen on initiation of protein synthesis in prostate

The initiation of protein synthesis by ribosomal particles of rat ventral prostate was studied by measuring ribosomal binding of an initiator (35-S)methionyl-tRNAf. The binding activity is dependent on ribosomes, GTP, and a prostate cytosol protein fraction. The 40S but not the 60S ribosomal subunit particles are active. The cytosol activity decreases rapidly within one hour after the rat is castrated. This loss is prevented by an intraperitoneal injection of 17beta-hydroxy-5-alpha-androstan-3-one (5-alpha-dihydrotestosterone). The cytosol activity can be stimulated almost immediately (within 10 min) after an intravenous injection of low dose (15 mug per rat) of 5-alpha-dihydrotestosterone into the castrated rat.