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E F Hahn

Publications and source records attributed to E F Hahn.

At least 19 recordsLinked to original sources
PubMed1994

Effects of the opioid antagonist naloxone on human natural killer cell activity in vitro.

Studies from several groups have shown that exogenous opiates as well as endogenous opioids may have direct or indirect effects on natural killer cell (NK) activity. Both enhanced and reduced NK activity have been reported in different in vivo and in vitro studies. The present study was performed to determine the effects of the opioid antagonist, naloxone, on human NK activity in vitro. Human peripheral blood mononuclear cells (PBMC) from 10 healthy normal subjects, as well as from 7 otherwise healthy methadone-maintained former heroin addicts, were used. These PBMC were incubated with a wide-concentration range (1 x 10(-12) to 1 x 10(-3) M) of (-)naloxone, the active enantiomer, and in parallel assays with (+)naloxone, the inactive enantiomer, prior to and during the NK activity assay. A significant reduction of NK activity by each enantiomer of naloxone was found only at very high concentrations, 1 x 10(-3) M (P < 0.01) and above. These concentrations are much higher than plasma levels of naloxone reached in humans during any therapeutic or research use of this opioid antagonist. This effect is probably due to an action at some site other than on classical opioid receptors. No effect was found at concentrations of naloxone below 1 x 10(-3) M. Thus, the data showed no naloxone-induced effects at concentrations of (-)naloxone which are sufficient to displace endogenous opioids from all types of classical opioid receptors, suggesting that the endogenous opioids that remained intact and bound to PBMC in vitro do not have any measurable modulatory effect on NK cell cytotoxicity activity.

Adult↗
PubMed1990

Activities of 3'-azido-3'-deoxythymidine nucleotide dimers in primary lymphocytes infected with human immunodeficiency virus type 1.

The relative antiviral potencies of five nucleotide heterodimers of 3'-azido-3'-deoxythymidine (AZT), 3'-azido-3'-deoxythymidilyl-(5',5')-2'-3'-dideoxy-5'-adenylic acid (AZT-P-ddA), 3'-azido-3'-deoxythymidilyl-(5',5')-2',3'-dideoxy-5'-inosinic acid (AZT-P-ddI), and the corresponding 2-cyanoethyl congeners AZT-P(CyE)-ddA and AZT-P(CyE)-ddI, were determined in primary human peripheral blood mononuclear cells infected with human immunodeficiency virus type 1. The homodimer 3'-azido-3'-deoxythymidilyl-(5',5')-3'-azido-3'-deoxythymidilic acid (AZT-P-AZT) was also included for comparison. The potencies of the compounds were AZT-P-ddA greater than or equal to AZT-P-ddI greater than AZT-P(CyE)-ddA greater than or equal to AZT-P(CyE)-ddI greater than or equal to AZT greater than AZT-P-AZT. Whereas AZT-P-ddA and AZT-P-ddI had in vitro therapeutic indices greater than that of AZT, the homodimer of AZT had a low therapeutic index. AZT-P-ddI exhibited the lowest toxicity in peripheral blood mononuclear, Vero, or CEM cells. Combination studies between AZT and 2',3'-dideoxyinosine (ddI) at nontoxic concentrations indicated a synergistic interaction at a drug ratio of 1:100. At higher ratios (1:500 and 1:1,000), the interactions were synergistic only at concentrations that produced up to 75% virus inhibition. At higher levels of antiviral effects, this combination was antagonistic, as determined by the multiple drug effect analysis method. AZT-P-ddI was about 10-fold less toxic than AZT to human granulocyte-macrophage progenitor cells. However, no significant difference was apparent when the compounds were evaluated against cells of the erythroid lineage. The greater antiviral activity and lower toxicity of this compound could not be attributed to the extracellular decomposition of the dimer in media at physiological temperature and pH. However, in acidic solutions, AZT-P-ddI decomposed in a pH-dependent manner. Advanced preclinical studies with this heterodimer of two clinically effective antiretroviral agents should be considered.

Cell Survival↗
PubMed1990

Naloxone benzoylhydrazone (NalBzoH) analgesia.

Naloxone benzoylhydrazone (NalBzoH) is a novel mixed agonist/antagonist. Against mu agonists, NalBzoH is a potent antagonist with a prolonged duration of action corresponding to its extremely slow rate of dissociation from mu receptors in binding assays. In the present studies, NalBzoH also antagonized mu analgesia, reversing both mu 1 and mu 2 analgesia independently elicited by intracerebroventricular or intrathecal [D-Ala2,MePhe4,-Gly(ol)5]enkephalin injections. It also antagonized kappa 1 analgesia elicited by U50,488H, and delta analgesia produced by intrathecal [D-Pen2,D-Pen5]enkephalin. Yet, at higher doses, NalBzoH alone produced analgesia in the tail-flick, hot plate and writhing assays. Neither the mu-selective antagonist beta-funaltrexamine, the delta-selective antagonist naltrindole, nor the kappa 1-selective antagonist norbinaltorphimine reversed NalBzoH analgesia in the tail-flick test. Analgesia observed with systemically administered NalBzoH was reversed easily by the antagonist WIN44,441 when it was given intracerebroventricularly, but not intrathecally. These observations confirm the opioid nature of NalBzoH analgesia and imply a supraspinal mechanism of action. In contrast, intrathecal, but not intracerebroventricular WIN44,441 reversed analgesia from systemic U50,488H quite potently. Thus, NalBzoH antagonizes mu, delta and kappa 1 actions while retaining its ability to elicit analgesia through a novel and distinct supraspinal kappa 3 system.

Analgesia↗
PubMed1989

Receptor binding of [3H]naloxone benzoylhydrazone: a reversible kappa and slowly dissociable mu opiate.

In standard 3H-opioid binding assays, the benzoylhydrazone derivative of naloxone (6-desoxy-6-benzoylhydrazido-N-allyl-14-hydroxydihydronormorphi none; NalBzoH) inhibited mu, kappa, and delta binding at nanomolar concentrations. At concentrations as low as 1 nM, it also produced a wash-resistant inhibition of opioid binding. [3H]NalBzoH binding typically gave a ratio of total to nonspecific binding of 8:1. Binding reached steady state levels by 1 hr and was linear with tissue concentration. [3H]NalBzoH labeled two classes of sites. The binding to one was easily reversible whereas the other was not and was termed pseudoirreversible. At 25 degrees, almost 90% of [3H]naloxone binding and approximately 60-75% of [3H]NalBzoH binding dissociated over 90 min. However, the remainder of [3H]NalBzoH binding, corresponding to pseudoirreversible binding, remained constant over the next 5 hr at 25 degrees and additional studies suggested a dissociation half-life of approximately 24 hr. Competition studies indicated that the reversible binding corresponded to neither mu nor delta binding and may represent a novel subtype of kappa receptor. Pseudoirreversible binding was predominantly to a combination of both mu 1 and mu 2 receptors. Despite its extremely slow rate of dissociation, pseudoirreversible binding was not covalent inasmuch as lowering the pH to 5 or adding the GTP analog 5'-guanylylimidodiphosphate [Gpp(NH)p] completely dissociated prebound [3H] NalBzoH. The ability of Gpp(NH)p to dissociate pseudoirreversible [3H]NalBzoH binding raised the possibility that the slow rate of dissociation was related to interactions with a guanine nucleotide-binding protein.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1989

Pharmacological actions of a novel mixed opiate agonist/antagonist: naloxone benzoylhydrazone.

NalBzoH (6-desoxy-6-benzoylhydrazido-N-allyl-14-hydroxydihydronomorphin one) is a novel opiate with potent actions at both mu and kappa receptors. Analgesic studies in mice examining increasing doses of NalBzoH with a fixed dose of morphine revealed a biphasic curve. NalBzoH at doses as low as 1 microgram/kg partially antagonized morphine analgesia. Higher NalBzoH doses continued to inhibit morphine analgesia in a dose-dependent manner, with the 1-mg/kg dose antagonizing completely morphine analgesia. As the NalBzoH dose increased beyond 1 mg/kg analgesia returned. NalBzoH also prduced a similar analgesic response when administered alone in mice and also was active in rats. NalBzoH had excellent p.o. activity, with an analgesic potency in mice equivalent to s.c. administration. Naloxone reversed NalBzoH analgesia far less effectively than morphine analgesia. In contrast, Win44,441 antagonized both morphine and NalBzoH analgesia with a similar potency, consistent with a kappa mechanism for NalBzoH analgesia. Repeated administration of NalBzoH resulted in tolerance. There was no analgesic cross-tolerance between NalBzoH and either morphine or the kappa 1-selective agent U50,488H, implying a selective kappa 3 mechanism of analgesia. In addition to blocking morphine analgesia, low doses of NalBzoH also partially reversed the inhibition of gastrointestinal transit in mice produced by morphine, antagonized completely morphine lethality and precipitated withdrawal in morphine-dependent mice, confirming its antagonist activity in mu receptors. The duration of NalBzoH's kappa and mu actions differed dramatically. In mice, analgesia typically lasted less than 2 hr whereas the same NalBzoH dose antagonized completely morphine analgesia, a mu action, for 16 hr. Full sensitivity to morphine did not return for 32 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1988

Differential sensitivity of opioid-induced feeding to naloxone and naloxonazine.

The high-affinity mu-1 opioid binding site has been implicated in some opioid responses (e.g., supraspinal analgesia) but not others (e.g., respiratory depression) by comparing the actions of naloxone, a short-acting, non-selective antagonist, and naloxonazine, an irreversible and selective mu-1 antagonist. The mu-1 site has been implicated in the opioid component modulating free feeding and deprivation-induced feeding, but not glucoprivic feeding. The present study compared naloxone and naloxonazine antagonism of hyperphagia induced by morphine, ethylketocyclazocine (EKC), dynorphin and d-ala2,d-leu5-enkephalin (DADL) in rats. Morphine produced a dose-dependent (0.01-5 mg/kg) hyperphagia in mildly food-deprived rats that was blocked by naloxone (0.01-10 mg/kg). Naloxonazine (10 mg/kg) shifted the morphine hyperphagia dose-response curve to the right. These effects could not be fully accounted for by the intrinsic hypophagic properties of these antagonists. EKC produced a dose-dependent (0.5-5 mg/kg) hyperphagia which was blocked by naloxone (10 mg/kg) only at low effective EKC doses. Naloxonazine (10 mg/kg) failed to affect EKC hyperphagia. Naloxone, but not naloxonazine also blocked dynorphin and DADL hyperphagia. These results indicate that feeding induced by opiate and opioid agonists are differentially mediated by the mu-1 and other opioid binding sites; these data contrast with the modulation by the mu-1 site of the supraspinal analgesia induced by each of these agonists.

Animals↗
PubMed1988

Irreversible opiate agonists and antagonists: V. Hydrazone and acylhydrazone derivatives of naltrexone.

We have synthesized a series of hydrazones and acylhydrazones of naltrexone. These substitutions had modest effects on competition of mu binding but many greatly enhanced the relative potency of the compounds for delta receptors. Increased delta affinity was most prominent with the acylhydrazones. Many of the derivatives elicited a wash-resistant inhibition of binding which was restricted to mu, not delta, binding sites. This wash-resistant inhibition of binding did not correlate with affinity, as determined by IC50 values, implying that the inhibition could not be explained simply by slow rate of dissociation due to increased affinity.

Animals↗
PubMed1988

Comparison of effects of chronic administration of naloxone and naloxonazine upon food intake and maintainance of body weight in rats.

A comparison of the effects of the short-acting opioid antagonist naloxone, with the irreversible and highly-specific mu-1 antagonist naloxonazine, has categorized the mediation of opioids in some forms of feeding into mu-1 and non-mu-1 components. The mu-1 sites have been implicated in free-feeding, deprivation-induced feeding and morphine-induced hyperphagia, based upon their sensitivity to both naloxone and naloxonazine. However, the ability of naloxone, but not naloxonazine to inhibit feeding, induced by either 2-deoxy-D-glucose glucoprivation, ethylketocyclazocine, dynorphin or (D-ala2., D-leu5.)-enkephalin implies the existence of non-mu-1 opioid receptor mechanisms in these responses. The present study compared the effects of the daily administration of naloxone and naloxonazine (10 mg/kg, i.v.) in rats in three different types of maturational or dietary situations. In adult rats, naloxonazine and naloxone significantly reduced body weight (7% and 4%, respectively) and food intake (21% and 13%, respectively) over 14 days. These effects were more pronounced in adolescent rats where naloxonazine and naloxone significantly reduced the gain in body-weight (53% and 33%, respectively) and food intake (24% and 15%, respectively) over 14 days. In the adolescent rats, the effects of naloxonazine were significantly greater than those of naloxone. In contrast, chronic treatment with neither naloxone nor naloxonazine altered body weight or food intake of rats made obese by dietary manipulations and left on that diet during treatment with antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1988

Nucleotide dimers suppress HIV expression in vitro.

A series of nucleotide homo- and heterodimers [3'-azido-3'-deoxythymidilyl-(5',5')-2',3'-di-deoxy-5' adenylic acid (AZT-P-ddA), 3'-azido-3'-deoxythymidilyl-(5',5')-2', 3'-dideoxy;-5'-adenylic acid, 2-cyanoethyl ester [AZT-P(CyE)-ddA], 3'-azido-3'-deoxythymidilyl-(5',5')-2',3'-dideoxy-5'-inosinic acid (AZT-P-ddI), and 3'-azido-3'-deoxythymidilyl-(5',5')-3'-azido-3'-deoxy-5'-thymid ilic acid (AZT-P-AZT)] were synthesized and compared with respect to their anti-HIV and cytotoxic properties to their component monomers in vitro. MT-2 cells were infected with HIV (TM) followed by the addition of drug. The dimers and their respective monomers inhibited HIV-induced syncytia formation, reverse transcriptase production, and the expression of HIV p24 antigen. However, on an equimolar basis, greater anti-HIV potency and enhanced cytotherapeutic indices were observed with the heterodimers when compared with their monomers. Nucleotide dimers, such as AZT-P-ddA, should be actively considered for further evaluation as anti-HIV agents.

Antiviral Agents↗
PubMed1988

Irreversible opiate agonists and antagonists. IV. Analgesic actions of 14-hydroxydihydromorphinone hydrazones.

Several phenylhydrazone derivatives of oxymorphone [phenylhydrazone and p-nitrophenylhydrazone (OxyPNPH)] as well as oxymorphonazine produce a wash-resistant inhibition of radiolabeled opioid binding, suggesting nonequilibrium binding to opiate receptors. All are agonists and, in an effort to correlate their prolonged inhibition of binding with their pharmacology, we examined their analgesic actions in vivo. Dose-response curves at 1 hr revealed similar potencies of oxymorphone and the derivatives, with the exception of OxyPNPH which was significantly less potent. After 10 hr, oxymorphone at doses up to 50 mg/kg did not demonstrate any effect. In contrast, OxyPNPH at 25 mg/kg elevated tail-flick latencies from 2 to over 8 sec after 10 hr. The 50-mg/kg dose elevated latencies to approximately 5 sec after 24 hr. Oxymorphonazine and oxymorphone phenylhydrazone also produced a prolonged analgesia, although not as effectively as OxyPNPH. The prolonged analgesic actions of OxyPNPH were highly dependent upon a critical period of 2 to 3 h immediately after injection. Blockade of receptors during this period with naloxone prevented analgesia at all time points examined. If the long duration of action of OxyPNPH resulted simply from a long half-life and persistent-free compound within the brain, analgesia should have returned by 8 hr, at which time naloxone has been eliminated. The absence of analgesia 8 hr after both OxyPNPH and naloxone argues against simple pharmacokinetic mechanisms for the prolonged analgesia and is consistent with persistent receptor occupation. OxyPNPH (25 mg/kg) administered in vivo lowered radiolabeled opioid binding effectively in brain membranes despite extensive washing. OxyPNPH lowered mu1 binding by approximately 60% and mu2 binding by 35% whereas delta binding was not lowered significantly.

Analgesia↗
PubMed1987

Oxymorphone-naltrexonazine, a mixed opiate agonist-antagonist.

Previous studies from our laboratories have reported the synthesis and pharmacological characteristics of a series of symmetrical opiate azines: naloxonazine, oxymorphonazine and naltrexonazine. We have now synthesized and characterized in binding assays and in vivo two asymmetrical azines: oxymorphone-naltrexonazine and oxymorphone-3-methoxynaltrexonazine. Oxymorphone-naltrexonazine, which theoretically could interact with the receptor as either an agonist or antagonist, displayed antagonist properties in vitro and in vivo. Oxymorphone-3-methoxynaltrexonazine, which theoretically could bind only as an agonist, possessed agonist properties in binding studies and was a potent analgesic in vivo.

Analgesia↗
PubMed1987

X-ray crystal structure of the opioid ligand naltrexonazine.

The anti-anti isomer of naltrexonazine (1) was synthesized, and its configuration was confirmed by X-ray crystallography. The syn-anti isomer is readily converted to 1 under acidic conditions. The apparent equal receptor binding of 1 and syn-anti isomer indicates that isomerization of the azine moiety may take place under the conditions of biological evaluation. Two possible explanations for wash-resistant binding of 1 to opioid receptors are presented. The first possibility involves a noncovalent interaction of the ligand with the opioid receptor, and the second considers covalent binding by a receptor-based sulfhydryl group.

Animals↗
PubMed1987

19-Hydroxylation and aromatization of androgens in the developing rat brain.

Androgen aromatization in the human placenta proceeds through two successive hydroxylations at C-19, the products of which are then virtually completely converted to estrogens. In the neonatal rat brain, however, 19-hydroxylation has been shown to exceed significantly subsequent aromatization, suggesting that formation of 19-hydroxylated androgen metabolites might be important in brain differentiation in this species. Using [19-3H3]androstenedione, we found that the surplus activity of 19-hydroxylase relative to aromatase was independent of age, sex, and androgen substrate concentration, despite 100-fold differences in tissue aromatase activity during the course of development. In addition, the surplus 19-hydroxylation was not affected by several agents which otherwise decreased or increased the activity of the aromatase enzyme, including metyrapone, KCN, and cytochrome P-450 reductase, the latter indicating that the failure of the 19-hydroxylated products to proceed to aromatization was not due to a deficit of reducing equivalents. 19-Hydroxylation of androgens in the rat brain is a quantitatively significant metabolic pathway in this tissue, although present data do not confirm the existence of a steroid C-19 hydroxylase in the brain separate from that involved in aromatization.

Androgens↗
PubMed1986

Absence of reactive intermediates in the formation of catechol estrogens by rat liver microsomes.

Release of 3H2O from regiospecifically labeled estradiol was measured during 2-hydroxylation of this estrogen by rat liver microsomes. The amount of tritium remaining in the isolated catechol estrogen was also determined. Virtually all the tritium was removed from C-2 during the reaction confirming the absence of an NIH shift. About 20% of the tritium at C-1 was also lost without any such change occurring at C-4 or C-6,7 of the steroid molecule. These findings provide evidence for the formation of an arene oxide or o-semiquinone intermediate during the conversion of estradiol to 2-hydroxyestradiol. No indication of adduct formation at either C-1 or C-4 during this biotransformation was obtained although the 2-hydroxylated product was able to react with a nucleophile such as glutathione. The different regiospecificity of tritium loss in the generation of catechol estrogens and in their subsequent reaction leads to the important conclusion that the reactive intermediates in the two processes must be different. The possible role of catechol estrogens in neoplastic transformation is discussed.

Animals↗
PubMed1985

Stereochemistry of 1,2-hydrogen loss during aromatization in the brain.

The stereochemistry of hydrogen loss from C-1 and C-2 during aromatization in rat brain was studied using androstenedione containing a known distribution of isotopic label. Comparison of the tritium content of the estrone obtained from the aromatization of androstenedione labeled predominantly in the 1 alpha,2 alpha positions with that in estrone obtained from a parallel incubation using substrate with label in the 1 beta,2 beta orientation gave an estrone alpha/beta ratio of 3.6. This ratio compares with a calculated value of 4.3 for an aromatization mechanism involving loss of the 1 beta,2 beta-hydrogens. The distortion from the predicted value is due to the loss of tritium from the alpha-substrate which is unrelated to aromatization. The ratio determined experimentally is compatible with 2 beta-tritium loss since random or alpha-elimination from C-2 would yield alpha/beta ratios of 2.2 and 1.3 respectively. In an analogous manner the stereochemistry of tritium loss at C-1 was determined using [1 alpha-3H] and [1 beta-3H]androstenedione. The alpha/beta ratio of the isolated estrone was 3.6 which is in good agreement with the calculated value of 3.3 for 1 beta-tritium elimination. Our results therefore show that estrogen formation in the brain occurs with the same stereospecificity of hydrogen loss at C-1 and C-2 as in placental microsomes.

Androstenedione↗
PubMed1985

Unexpected effects of nalmefene, a new opiate antagonist, on the hypothalamic-pituitary-gonadal axis in the male rat.

In order to gain additional information on the role of brain opioid peptides in the regulation of the hypothalamic-pituitary-gonadal axis, we studied the effects of nalmefene, a new opiate antagonist, on gonadotropin and testosterone secretion in male rats. The results were compared with those obtained with naloxone, a well-studied antagonist. Acute injections of either nalmefene or naloxone (2 mg/kg) produced 4-fold increases in LH and testosterone secretion. In castrated male rats treated with testosterone propionate (TP), nalmefene (10 mg/kg) reversed the androgen negative feedback on LH secretion; surprisingly, when higher doses (25 and 50 mg/kg) were injected, the compound lost its ability to antagonize the testosterone-induced inhibition of LH levels. In contrast, naloxone was able to increase LH levels in TP-treated castrated rats even at the highest dose tested (50 mg/kg). Chronic administration of these antagonists resulted in suppression of the acute release of LH and T secretion in nalmefene-treated but not in naloxone-injected animals. These data are consistent with previous observations suggesting that opioid peptides a) exert a tonic inhibitory effect on LH and testosterone production and b) participate in the negative androgen-induced feedback control of LH secretion. Our results also show that the antagonistic action of nalmefene, but not naloxone, is reversed when higher doses are used or following chronic administration.

Animals↗
PubMed1985

19-Hydroxylation of androgens in the rat brain.

Aromatization of androgens in the central nervous system is linked with sexual differentiation of the brain and, thus, determines the nature of sexual behavior and the control of gonadotropin secretion. The process of aromatization, as determined in the human placenta, proceeds through two successive hydroxylations at C-19, the products of which are then virtually completely converted via a third hydroxylation at C-2 to estrogens. We now report that in the rat brain, 19-hydroxylation of androgens greatly exceeds aromatization and the 19-hydroxy- and 19-oxoandrogen products accumulate in quantities 5 times greater than the estrogens. This relationship implies that the aromatization sequence in the brain is deficient in the terminal hydroxylase, and the process is distinct from that in other tissues. The function of 19-hydroxy- and 19-oxotestosterone in the central nervous system is unknown but, unlike the reduced or aromatized metabolites of the male hormone, these substances cannot be delivered from the circulation and their presence in the brain is totally dependent on in situ formation, making them logical candidates for modulators of neuronal functions.

Androgens↗