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Biomedical subjects

E F Hahn

Publications and source records attributed to E F Hahn.

At least 37 records · Page 2Linked to original sources
PubMed1985

Castration affects male rat brain opiate receptor content.

We previously reported that saturable stereospecific binding of [3H]-naltrexone in rat brain homogenates prepared from castrated male rats was greater than the corresponding binding in intact animals. We now report that we have replicated these results and that the difficulty of other investigators in observing these differences is due to methodological factors. Specifically, when samples were filtered individually and rapidly, differences between castrated and intact rats were maintained. The increase in binding was also observed when tissues were washed to remove endogenous opioids prior to incubation, when [3H]-naloxone was used as the ligand, and when various antagonists were used as displacers in the radioreceptor assay.

Animals↗
PubMed1985

Effect of sodium chloride on opiate receptor binding in spontaneously hypertensive rats: dependence on age.

The effect of 100 mM sodium chloride on the binding of [3H]-naltrexone to rat brain opiate receptors in spontaneously hypertensive (SHR) and normotensive (WKY) rats was studied. The percentage increase in binding in the presence of sodium chloride did not vary with age in WKY rats. Brain homogenates from 4 week old SHR rats incubated with 100 mM sodium chloride exhibited a similar increase in binding compared to age matched WKY rats. In contrast, brain preparations from 6, 14 and 20 week old SHR rats were more sensitive to sodium chloride, and the increase in binding of [3H]-naltrexone was significantly greater in these animals than in corresponding normotensive ones. Since blood pressure is increased in SHR rats compared to WKY rats at these ages, these results suggest that elevated blood pressure may be correlated with an increase in opiate receptor sensitivity to sodium chloride. The effect of in vivo sodium chloride was examined by feeding the animals a diet containing 4% salt. This concentration of salt did not significantly alter the binding of [3H]-naltrexone to rat brain homogenates prepared from 8 week old SHR rats. These results suggest that higher levels of sodium chloride and longer exposure to the diet may be required to observe the salt sensitivity produced by 100 mM salt in the in vitro radioreceptor assay.

Animals↗
PubMed1985

Irreversible opiate agonists and antagonists. II. Evidence against a bivalent mechanism of action for opiate azines and diacylhydrazones.

A series of opiate azines, including naloxonazine, naltrexonazine and oxymorphonazine, produce both a wash-resistant inhibition of 3H-opioid binding and prolonged actions in vivo. Opiate diacylhydrazones synthesized from succinic, adipyl and suberic dihydrazides possess similar actions against 3H-opioid binding. Competition studies measuring inhibition of binding in the presence of the compounds revealed little difference between standard, reversible opiates such as naloxone, oxymorphone and naltrexone and our two series of compounds, the diacylhydrazones and the azines. In these assays, the diacylhydrazones, the azines, oxymorphone, naloxone and naltrexone all inhibited 3H-opioid binding with very similar IC50 values, typically under 5 nM. At concentrations under 5 nM, the inhibition of all the compounds was reversible. At higher concentrations, however, much of the inhibition of the diacylhydrazones and azines was not freely reversible, in distinction to oxymorphone, naloxone and naltrexone. Washing after the incubation of membranes with the naloxone, naltrexone or oxymorphone (50 nM) returned binding to control levels. Despite the extensive washing, the diacylhydrazones, on the other hand, lowered binding by as much as 90%. Mu binding was most sensitive to wash-resistant binding. In general, the longer dihydrazide derivatives produced wash-resistant inhibition more effectively than either the shorter dihydrazide derivatives or the corresponding azines. The ability of these compounds to produce wash-resistant inhibition of binding probably did not result from a bivalent attachment of the ligand to two binding sites at once. Additional assymetric azines and diacylhydrazones unable to bind simultaneously to two sites still produced wash-resistant inhibition of binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Irreversible opiate agonists and antagonists. III. Phenylhydrazone derivatives of naloxone and oxymorphone.

In view of previous studies indicating that the irreversible properties of opiate azines such as naloxonazine are not due to a bivalent mechanism, we have synthesized a series of opiate hydrazones. In standard competition assays which measure both reversible and irreversible inhibition of binding, the hydrazone derivatives lowered radiolabeled opioid binding almost as well as naloxone and oxymorphone. However, the phenylhydrazone derivatives produced a profound wash-resistant inhibition of binding. The similar potencies of the methylhydrazine and phenylhydrazine derivatives in standard competition studies contrasted significantly with their effectiveness in eliciting wash-resistant inhibition of binding, suggesting the importance of the phenyl group in the production of wash-resistant inhibition. The p-nitrophenyl hydrazones were the most effective wash-irreversible inhibitors. Although oxymorphonazine does not irreversibly inhibit radiolabeled opioid binding as effectively as naloxonazine or naltrexonazine, the oxymorphone phenylhydrazones were as potent as their corresponding naloxone compounds. Incubation of [3H]naloxone-p-nitrophenylhydrazone with albumin demonstrated significant incorporation of radiolabel into the protein after sodium dodecylsulfate gel electrophoresis. This suggests that the phenylhydrazones have significant reactivities toward proteins and might produce their irreversible actions through covalent interactions.

Albumins↗
PubMed1985

Testing and evaluation of opiate analgesics and antagonists.

In recent years many advances have been made in our understanding of how opiates function as modulators of pain. These discoveries have in turn led to substantial improvements in the methodology available for the testing of newly synthesized opiates. Preliminary in vitro assays can now define opiate receptor selectivity and also classify a drug as a pure or mixed agonist-antagonist. These results can then be verified by in vivo behavioral or neurochemical studies using laboratory animals. This protocol, which involves tests that are relatively simple and inexpensive to conduct, yields reproducible results which provide insight into the study design required for the clinical evaluation of the new agents. Considering the complexity of the problem involved in modifying the pharmacological profile of an opiate, the progress that has been made in the methodology for evaluating these substances is commendable.

Analgesics, Opioid↗
PubMed1984

Immunological probe of estrogen biosynthesis. Evidence for the 2 beta-hydroxylative pathway in aromatization of androgens.

The terminal hydroxylation in placental estrogen biosynthesis from androgens is at the 2 beta position. The 2 beta-hydroxy-19-oxoandrogen derivative collapses nonenzymatically to estrogen and is therefore the proximate precursor of the female hormone. To establish the role of this pathway in biological aromatization, an immunological approach was employed in which an antibody was obtained which recognizes 2 beta-hydroxy-19-oxygenated androgens but not intermediates oxygenated at C-19 only. Binding of the 2 beta-hydroxy-19-oxo intermediate by the antibody stabilizes it so that its nonenzymatic transformation to estrogen is delayed and results in slower estrogen formation. When placental microsomes were incubated with [1,2-3H]androstenedione in the presence of the antibody antiserum, a 50% decrease in [3H]estradiol formation and 3H2O release was observed when compared with identical incubations containing normal rabbit serum alone. This inhibition is blocked when the antibody is inactivated by presaturation with 2 beta, 19-dihydroxyandrostenedione. Precipitation of immunoglobulins from the incubations followed by heating liberated the 2 beta-hydroxy-19-oxo intermediate (30%) from the antibody, and resulted in its nonenzymatic collapse to estrogen with concomitant release of 3H2O. Control normal rabbit serum or blocked antibody incubations did not show a similar increase in [3H]estradiol or 3H2O yields in the precipitate. Heat treatment (90 degrees C) of the antibody but not normal rabbit serum incubations resulted in a similar increase in [3H]estradiol and 3H2O yields. These results are consistent with the hypothesis that the final and rate-determining hydroxylation in aromatization of androgens is at the 2 beta position and that this pathway is the dominant, if not the sole, route of estrogen biosynthesis by placental aromatase. The antibody probe also permits the characterization of aromatization mechanisms in tissues other than the placenta.

Androgens↗
PubMed1984

Chronic naloxone increases opiate binding in SHR and WKY rats.

We have previously reported that chronic administration of naloxone to SHR and WKY rats results in a significant increase in their systolic blood pressure relative to control animals. In the present study we show that chronic naloxone is also accompanied by a marked increase in the number of brain opiate receptors. Although the relative difference in blood pressure diminishes with increasing maturity, the elevation in brain opiate receptors remains in the treated animals. Mechanisms for these differential effects are discussed.

Aging↗
PubMed1984

Catechol estrogen formation and metabolism in brain tissue: comparison of tritium release from different positions in ring A of the steroid.

Catechol estrogens labeled with 3H at different positions in rings A and B of the steroid were synthesized by chemical or enzymatic methods, and their oxidative transformation by male rat brain microsomes was followed by the transfer of 3H into 3H2O. This reaction was shown to occur more readily with the catechol estrogens than with the parent steroid and was also influenced by the position of the radiolabel. Tritium was displaced less readily from C-1 than from C-2 or C-4 of the aromatic ring. Spermine, which is known to increase cytochrome P-450-mediated hydroxylation reactions, had no effect on the release of 3H from ring A of either estradiol or 2-hydroxyestradiol with rat brain microsomes in contrast to liver. Glutathione and other thiols were able to cause a rapid loss of 3H from labeled catechol estrogens, even in the absence of tissue, but in double label experiments with [4-3H]- and [4-14C]2-hydroxyestradiol, the isotope ratio in the recovered catechol estrogen was unchanged. The results illustrate some of the problems in determining accurately the metabolism of estrogens by measuring 3H2O formation when aromatic hydroxylation is involved and also highlight the possible interaction of the catechol estrogens with cellular nucleophiles such as glutathione.

Animals↗
PubMed1984

Interaction of naloxone and sodium chloride intake on body weight gain in WKY and SHR rats.

Although a possible role for endogenous opioids in the regulation of feeding behavior has been proposed, little direct information is available concerning the impact of long term opiate antagonist treatment on body weight. Therefore, the effect of chronic exposure to naloxone on body weight was examined in WKY and SHR rats. Since the affinity of opiate antagonists for the receptor is increased by the presence of sodium ions, body weight was also determined in animals receiving a diet containing either 0.48% or 4% sodium chloride. Naloxone does not affect body weight in either strain of animals fed a normal (0.48% NaCl, Purina) diet. However, WKY rats fed the diet elevated in sodium chloride showed an increase in body weight which is blocked by treatment with naloxone. In contrast, SHR rats fed this diet weighed less than control animals receiving the normal diet, and naloxone did not decrease their weights further. These results suggest that naloxone may impact on mechanisms which regulate body weight, but is not capable of decreasing weight below a set point in either WKY or SHR rats.

Animals↗
PubMed1983

Naloxone, a specific opioid antagonist, reverses chronic idiopathic constipation.

Two patients with long-standing idiopathic chronic constipation, which responded only to large daily doses of laxatives and additional suppositories and enemas, were treated with the specific opioid antagonist, naloxone, on a single-blind crossover basis. Both patients responded to naloxone treatment, with increased passage of faeces and increased wet and dry faecal weight. Although naloxone is poorly absorbed after oral administration, there was a positive response during oral as well as intravenous treatment, suggesting that the primary effect of naloxone is at specific opiate receptor sites in the myenteric plexus and other neural and endocrine cells of the intestinal wall.

Administration, Oral↗
PubMed1982

Irreversible opiate agonists and antagonists: the 14-hydroxydihydromorphinone azines.

Further investigations into the molecular actions of the 14-hydroxydihydromorphinone hydrazones (naloxazone, oxymorphazone, and naltrexazone) have suggested that their irreversible actions can be explained by the formation of their azines. These azines, naloxonazine, naltrexonazine, and oxymorphonazine, irreversibly block opiate binding in vitro 20- to 40-fold more potently than their corresponding hydrozones, naloxazone, naltrexazone, and oxymorphazone. The blockade of binding by naloxonazine shows the same selectivity for high affinity, or mu1, sites as naloxazone.

Animals↗
PubMed1980

Long-acting opiate agonists and antagonists: 14-hydroxydihydromorphinone hydrazones.

Two new long-acting hydrazone derivatives of 14-hydroxydihydromorphinones have been synthesized, oxymorphazone and naltrexazone. Both derivatives show high affinity for opiate binding sites in vitro, similar to naloxazone, the hydrazone analogue of naloxone. Sodium and manganese shifts imply that naltrexazone, like naloxazone, is a pure antagonist. By contrast, oxymorphazone inhibition of receptor binding is dramatically reduced by sodium and potentiated by manganese, suggesting it is an agonist. When given in vivo, all agents produce a significant inhibition of receptor binding for over 24 h despite extensive washing of the brain homogenates. Oxymorphone, naltrexone, and naloxone are without effect. Twenty-four hours after in vivo administration of oxymorphazone, 82% of mice are still analgetic compared to only 17% of oxymorphone-treated mice (p less than 0.005). Twenty-four hours after naltexazone or naloxazone treatment all mice were protected from morphine analgesia (12 mg/kg; p less than 0.005), while naltrexone- and naloxone-treated animals did not differ significantly from saline-treated controls.

Analgesics, Opioid↗
PubMed1980

Opiate regulation of estradiol-2-hydroxylase in brains of male rats: mechanism for control of pituitary hormone secretion.

Treatment of male rats with a single high dose of morphine (10 mg/kg, subcutaneously) results in a dramatic suppression of brain estradiol-2-hydroxylase activity. The suppression is blocked by naloxone and is decreased upon the development of tolerance. The injection of naloxone (0.4 mg/kg) alone produces a significant increase in brain estradiol-2-hydroxylase activity over control levels. The effects of the opiate agonists and antagonists on the activity of this brain enzyme coincide in degree and direction with their effects on plasma lutropin (luteinizing hormone) concentrations. Because the 2-hydroxyestrogens were shown to induce pituitary lutropin release, the present results indicate that the action of opiates, endogenous or exogenous, on pituitary gonadotropin release can be mediated by brain catechol estrogens.

Animals↗