Effects of a novel fentanyl derivative on drug discrimination and learning in rhesus monkeys.

Three monkeys discriminated 1.78 mg/kg of mirfentanil while responding under a fixed-ratio 5 schedule of stimulus-shock termination. Two mirfentanil derivatives, OHM3295 and OHM10579, substituted for mirfentanil in all subjects. However, other drugs produced variable effects among monkeys; for example, mu and kappa opioid agonists and clonidine substituted for mirfentanil on some occasions in two monkeys. Cocaine, amphetamine, and ketamine did not substitute in any subject. Opioid antagonists did not attenuate the effects of mirfentanil. In monkeys responding under a repeated acquisition and performance procedure, errors increased only during the acquisition phase at doses of mirfentanil that decreased response rates. Thus, unlike fentanyl, the discriminative stimulus effects of mirfentanil do not appear to be mediated exclusively through opioid receptors. Finally, mirfentanil does not appear to disrupt complex behavioral processes.

Daily mirfentanil induces (cross-) tolerance to the rate-decreasing effects of morphine and not mirfentanil.

The fentanyl derivative mirfentanil has a novel set of behavioral effects in non-humans including low-efficacy opioid actions and non-opioid antinociceptive actions. This study evaluated the rate-decreasing effects of mirfentanil, morphine, naltrexone and ketamine in pigeons both prior to and during a period of chronic treatment with mirfentanil (3.2-17.8 mg/kg/day). Daily treatment with mirfentanil did not modify the rate-decreasing effects of mirfentanil or ketamine; however, daily treatment decreased sensitivity to the rate-decreasing effects of morphine and increased sensitivity to naltrexone. These results demonstrate a lack of tolerance to an apparently non-opioid action (rate-decreasing effect) of mirfentanil, which might predict a lack of tolerance to the non-opioid antinociceptive actions of this compound. These results further indicate that cross-tolerance (to morphine) and dependence (increased sensitivity to naltrexone) can occur in the absence of tolerance (to mirfentanil).

Pharmacological profile of a deuterium-substituted mirfentanil derivative, OHM10579, in rhesus monkeys.

The discriminative-stimulus, respiratory, and antinociceptive effects of OHM10579, an isotopic isomer of mirfentanil, were characterized in rhesus monkeys. In monkeys discriminating nalbuphine, 0.32 mg/kg of OHM10579 partially substituted for nalbuphine. In monkeys treated daily with 3.2 mg/kg of morphine and discriminating 0.01 mg/kg of naltrexone, 0.32 mg/kg of OHM10579 substituted for naltrexone. In morphine-abstinent monkeys, morphine reversed naltrexone-lever responding, an effect attenuated by OHM10579. The shift to the right in the morphine dose-effect curve was greater 2 h after 0.32 mg/kg of OHM10579 compared to 0.32 mg/kg of mirfentanil, indicating that OHM10579 has a longer duration of action than mirfentanil. In a warm-water tail-withdrawal procedure, 10 and 17.8 mg/kg of OHM10579 had antinociceptive effects that were not antagonized by naltrexone. Morphine decreased breathing in air to 48%, whereas the maximal decrease with OHM10579 was to 75% of control. OHM10579 attenuated hyperventilation induced by 5% CO2 and partially antagonized the respiratory-depressant effects of morphine. OHM10579 can be classified as a low-efficacy mu-opioid agonist with some nonopioid actions. These results indicate that the pharmacology of the mirfentanil isotope OHM10579 is similar to that of mirfentanil, but that OHM10579 might have a longer duration of action.

The rate-decreasing effects of fentanyl derivatives in pigeons before, during and after chronic morphine treatment.

Mirfentanil is a fentanyl derivative with non-opioid actions, including non-opioid antinociceptive effects in rhesus monkeys. The current study examined the rate-altering effects of mirfentanil and several other compounds in pigeons to assess: 1) the opioid and non-opioid actions of acutely-administered fentanyl derivatives; and 2) the development of cross-tolerance between each of these compounds and morphine. Seven pigeons responded under a fixed-ratio 20 (FR20) schedule of food delivery. In untreated pigeons, fentanyl, morphine, naltrexone, ketamine and three fentanyl derivatives (mirfentanil, OHM3463 and OHM3295) decreased rates of key pecking in a dose-related manner. Naltrexone (0.1-1.0 mg/kg) attenuated the effects of OHM3463 and not mirfentanil or OHM3295, suggesting non-opioid mediation of the rate-decreasing effects for the latter two fentanyl derivatives. Subjects were treated daily with morphine for 9 weeks, up to a dose of 100 mg/kg per day, during which time the dose-effect curves for morphine, fentanyl and OHM3463 shifted rightward 6-, 10- and 2-fold, respectively, indicating the development of tolerance to morphine and cross-tolerance to fentanyl and OHM3463. Dose-effect curves for ketamine, OHM3295 and mirfentanil were not shifted to the right during morphine treatment, and the dose-effect curve for naltrexone was shifted leftward 180-fold. To the extent that rate-decreasing effects are predictive of antinociceptive effects, these data suggest that some fentanyl derivatives might be useful therapeutics under conditions where tolerance develops to morphine-like opioids.

Behavioral effects and binding affinities of the fentanyl derivative OHM3507.

Several fentanyl derivatives have been reported to have novel pharmacologies that might be exploited for developing alternate approaches to the treatment of pain. The purpose of the current series of studies was to evaluate OHM3507, a novel fentanyl derivative reported to have an unusual pharmacological profile in nonprimate species. Similar to several other fentanyl derivatives with clinical potential, OHM3507 had the highest affinity (IC50 = 10 nM) for mu ([3H]D-Ala2,N-Me-Phe4,Gly5-OH-labeled) receptors with 6- and 176-fold lower affinity for delta ([3H]D-Pen2-D-Pen5-labeled), and kappa ([3H]ethylketocyclazocine-labeled) receptors, respectively. In rhesus monkeys, OHM3507 shared discriminative stimulus effects with morphine, increased tail-withdrawal latencies in a warm-water procedure of antinociception, decreased ventilation in monkeys breathing normal air or 5% CO2, and failed to modify accuracy on acquisition and performance tasks up to doses that decreased rates of food-maintained responding. The opioid antagonists naltrexone and naltrindole antagonized the behavioral effects of OHM3507 in a manner that was consistent with mu-receptor mediation. Although OHM3507 appeared to have low efficacy opioid actions in nonprimate species, results from the current studies clearly show this compound to have strong, fentanyl-like mu agonist actions in rhesus monkeys. These results provide another example of the sometimes poor predictability in the behavioral pharmacology of fentanyl derivatives among species, in this case between monkeys and rats, mice and rabbits, and demonstrates the need for evaluating new drugs under a broad range of conditions to increase the probability of identifying novel compounds that can be used to treat pain.

Mirfentanil antagonizes morphine-induced suppression of splenic NK activity in mice.

Mirfentanil [N-(2-pyrazinyl)-N-(1-phenethyl-4-piperidinyl)-2-furamide] was studied for its antinociceptive and immunomodulatory effects in mice Mirfentanil (1.0-32.0 mg/kg) increased tail-flick latency to a thermal stimulus and this effect was antagonized (94 +/- 2%) by naltrexone (10.0 mg/kg). Unlike naltrexone, the delta opioid selective antagonist naltrindole (20.0 mg/kg) had no effect on mirfentanil-induced analgesia. In a dose-dependent fashion, the mu-selective antagonists beta-funaltrexamine (1.0-40.0 mg/kg) and naloxonazine (1.0-35.0 mg/kg) blocked mirfentanil (10.0 mg/kg)-induced analgesia up to 75% of the maximum analgesic effect. Norbinaltorphimine (10.0 mg/kg) partially blocked (35%) the maximum analgesic effect following mirfentanil (10.0 mg/kg) administration. Single doses of mirfentanil (0.1-32.0 mg/kg) had no effect on splenic NK activity. However, preadministration of mirfentanil (1.0-10.0 mg/kg) blocked morphine-induced suppression of splenic NK activity. Collectively, the results suggest that mirfentanil is a novel opioid that induces antinociception predominately through mu opioid receptors but, unlike morphine or fentanyl, does not suppress splenic NK activity.

Fentanyl-related 4-heteroanilido piperidine OHM3295 augments splenic natural killer activity and induces analgesia through opioid receptor pathways.

Recently, the fentanyl-related compound OHM3295 has been shown to induce a naltrexone-sensitive, dose-related analgesia in CD1 mice. However, unlike morphine or fentanyl, which are potent immunosuppressive drugs, OHM3295 has been found to augment splenic natural killer (NK) activity in a dose-related and naltrexone-reversible manner. The present study investigated the type (delta, kappa or mu) of opioid receptor involved in analgesia and immunomodulation after acute administration of OHM3295. CD1 mice pretreated with beta-funaltrexamine (beta-FNA, 40.0 mg/kg) showed an insignificant induction of analgesia (8.4 +/- 3.7%) after 3.2 mg/kg OHM3295, whereas mice pretreated with vehicle, norbinaltorphimine (10.0 mg/kg) or naltrindole (20.0 mg/kg) exhibited 43.6 +/- 12.6% of maximal analgesia, as determined by the tail-flick latency test. Consistent with previous results, acute administration of OHM3295 (3.2 mg/kg) augmented splenic NK activity (20.7 +/- 3.4 lytic units [LU]) relative to vehicle-treated mice (8.2 +/- 0.7 LU). Pretreatment with beta-FNA (40.0 mg/kg) completely blocked (9.0 +/- 1.9 LU) OHM3295-mediated augmentation of NK activity, whereas pretreatment with norbinaltorphimine (10.0 mg/kg) partially blocked (15.8 +/- 2.2 LU) the drug-induced effect. However, pretreatment with naltrindole (20.0 mg/kg) did not antagonize OHM3295-induced increases in splenic NK activity but rather further enhanced (32.3 +/- 4.2 LU) the effect. NK-enriched effector cells from OHM3295-treated mice displayed an increase in conjugation with YAC-1 target cells, an increase in the percent killing of target cells and a significant increase in the number of active killer cells compared with NK-enriched effector cells from vehicle-treated mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral effects and receptor binding affinities of fentanyl derivatives in rhesus monkeys.

These studies examined the opioid receptor binding affinities and behavioral effects of several fentanyl derivatives in rhesus monkeys. OHM3295, OHM3296, OHM3326 and OHM3463 displayed high affinity for mu (IC50 = 7-66 nM) as compared to kappa (IC50 = 263-3255 nM) or delta (IC50 = 480-4500 nM) receptors as measured by their ability to displace [3H](D-Ala2-Me-Phe4,Glyol5)enkephalin, [3H](5,7,8[beta])-N-[2- (1-pyrrolidinyl)1-oxaspiro[4,5]dec-8-yl]benzeneacetamide and [3H](D-Pen2-D-Pen5)enkephalin, respectively. All four compounds maintained i.v. self-administration responding at rates above those maintained by the mu agonist alfentanil. In drug discrimination studies, OHM3463, OHM3326 and OHM3296 substituted completely for nalbuphine whereas OHM3295, and a related compound, mirfentanil, substituted partially for nalbuphine. In morphine-treated monkeys, OHM3295 substituted for naltrexone; in monkeys acutely deprived of morphine, only OHM3463 reversed naltrexone-lever responding. All four compounds had antinociceptive effects, although the extent to which these effects were accompanied by respiratory depression or modified by naltrexone, as well as the interactions between antinociceptive effects of fentanyl derivatives and alfentanil, varied markedly among compounds. Thus, OHM3463 shared effects with mu agonists (e.g., alfentanil) under all conditions; the other three compounds had opioid agonist effects under only a subset of conditions. Moreover, one of these compounds (OHM3295) antagonized the discriminative stimulus and antinociceptive effects of other mu agonists. Collectively, these compounds appear to vary on two dimensions: opioid efficacy and the contribution of nonopioid actions to their antinociceptive effects. Together with results obtained with other fentanyl derivatives (mirfentanil) under similar conditions, results of the current study suggest this chemical class might be especially fertile for the development of novel analgesics that might have reduced toxicity and abuse liability as compared to fentanyl and related compounds that are currently used in medicine.

OHM3295: a fentanyl-related 4-heteroanilido piperidine with analgesic effects but not suppressive effects on splenic NK activity in mice.

The immunoregulatory effects of fentanyl and a fentanyl-related compound, OHM3295, were studied in mice. Male CD1 mice treated with a range of fentanyl doses (0.1-1.0 mg/kg, subcutaneously) showed suppression of splenic natural killer (NK) activity following 0.25-0.50 mg/kg fentanyl dose but not higher (0.75-1.0 mg/kg) or lower (0.1 mg/kg) doses. Fentanyl (0.01-32.0 mg/kg) also induced dose-related analgesia as measured by an increase in tail flick latency; these analgesic effects were antagonized by naltrexone (1.0-10.0 mg/kg). Pretreatment with naltrexone (1.0-3.2 mg/kg) resulted in significant suppression of splenic NK activity following fentanyl (10.0-32.0 mg/kg) administration. In comparison to fentanyl, OHM3295 (3.2-25.0 mg/kg) augmented splenic NK activity in a naltrexone-reversible manner. Similar to fentanyl, OHM3295 (1.0-32.0 mg/kg) also induced a naltrexone-sensitive, dose-related analgesia as measured by an increase in tail flick latency. These results with OHM3295 demonstrate a novel profile of effects which includes naltrexone-sensitive analgesic effects in the absence of immunosuppressive effects. In addition, this is the first reported case in which a compound with opioid analgesic effects has been shown to potentiate natural killer cytolytic activity following in vivo administration.

New 1-(heterocyclylalkyl)-4-(propionanilido)-4-piperidinyl methyl ester and methylene methyl ether analgesics.

A series of new 1-(heterocyclyalkyl)-4-(propionanilido)-4-piperidinyl methyl esters and methylene methyl ethers have been synthesized and pharmacologically evaluated. In the mouse hot-plate test, the majority of compounds exhibited an analgesia (ED50 less than 1 mg/kg) superior to that of morphine. These studies revealed a pharmacological accommodation for many more structurally diverse and far bulkier aromatic ring systems than the corresponding components of the arylethyl groups of the prototypic methyl ester (carfentanil, 2) and methylene methyl ether (sufentanil, 3 and alfentanil, 4) 4-propionanilido analgesics. Compound 9A (methyl 1-[2-(1H-pyrazol-1-yl)-ethyl]-4-[(1-oxopropyl)phenylamino]-4- piperidinecarboxylate), which exhibited appreciable mu-opioid receptor affinity, was a more potent and short-acting analgesic, than alfentanil with less respiratory depression in the rat. On the other hand, the phthalimides 57A and 57B, which exhibited negligible affinity for opioid receptors associated with the mediation of nociceptive transmission (i.e., mu-, kappa-, and delta-subtypes), displayed analgesic efficacy in all antinociception tests. In addition, while 57B, compared to clinical opioids, showed a superior recovery of motor coordination after regaining of righting reflex from full anesthetic doses in the rat rotorod test, 57A showed significantly less depression of cardiovascular function at supraanalgesic doses in the isoflurane-anesthetized rat.

New 4-(heteroanilido)piperidines, structurally related to the pure opioid agonist fentanyl, with agonist and/or antagonist properties.

A research program based on certain heterocyclic modifications (12-50) of the fentanyl (1) molecule has generated a novel class of opioids. In the mouse hot-plate test, these compounds were weaker analgesics than 1. Two types of antagonists were observed in morphine-treated rabbits: those (e.g., 28) that reversed both respiratory depression and analgesia and those (e.g. 32) that selectively reversed respiratory depression. Evaluation of in vitro binding affinities to rat brain opioid receptors was inconclusive for a common locus of action for the agonist as well as the antagonist component. Further pharmacological evaluation of 32, N-(2-pyrazinyl)-N-(1-phenethyl-4-piperidinyl)-2-furamide, in the rat showed it to be a potent analgesic (ED50 = 0.07 mg/kg, tail-flick test) with little cardiovascular and respiratory depression when compared to fentanyl.

Synthesis and estrogen receptor selectivity of 1,1-bis(4-hydroxyphenyl)-2-(p-halophenyl)ethylenes.

A series of triarylethylenes (1a-e) were synthesized and evaluated for their ability to compete with [3H]estradiol for high-affinity estrogen receptors (ER) in immature rat uterine cytosol. All compounds showed affinity comparable to that of estradiol, with 1c having the highest affinity and the lowest calculated nonspecific binding of the para-halogenated members. Compound 1a had a higher affinity than did its chlorovinyl counterpart 1b, indicating that a vinyl hydrogen was suitable for high ER affinity in this series. Compound 1c was labeled with 3H ortho to one or both of its hydroxyls. Its ratio of specific to nonspecific binding in rat uterine cytosol, 3.2, was 140% of that of a related triarylethylene, 4-hydroxytamoxifen, and was 24% that of estradiol. Administration of [3H]-1c to immature female rats resulted in accumulation of 3H in uterine tissue which was decreased 39% when [3H]-1c was coadministered with estradiol. The major site of accumulation 1, 4, and 8 h after administration was in the intestinal tract. Chromatographic analysis showed that levels of 1c were less than those of 1c glucuronide in blood plasma, liver, and intestinal contents of rats 1 h after administration of 1c. Uterine 3H was comprised of 85% of 1c and 11% of 1c glucuronide. These results indicate that 1c undergoes ER-mediated uptake in the immature female rat, but selectivity is reduced due to nonspecific accumulation of free and conjugated 1c in uterine tissue.

Metabolism of nitromiphene (CI 628) in the immature female rat: role of gastrointestinal microflora in the biotransformation of a triarylethylene antiestrogen.

Nitromiphene (NIT; CI 628) is a triarylethylene antiestrogen shown to be effective in treatment of experimental breast cancer. We have studied the fate of NIT in the immature female rat, the animal model in which most of the biochemical studies of NIT have been carried out. NIT was eliminated mainly via the feces after i.p. administration, primarily as metabolites. One of these, a diphenylmethane derivative, p-[2-(N-pyrrolidinyl)ethoxy]-p'-methoxybenzophenone (PMB), was also eliminated in urine as such and as its O-demethyl and keto-reduced metabolites. In uterine and liver tissue, unchanged NIT was accompanied by demethyl NIT (CI 628M), PMB, and a diarylacetophenone derivative, p-[2-(N-pyrrolidinyl)ethoxy-p'-hydroxybenzhydryl phenyl ketone (demethyl KET). In vitro studies showed that O-demethyl NIT was produced in the presence of liver enzymes and that PMB and demethyl KET were produced in the presence of intestinal bacteria. These results suggested that PMB and demethyl KET accumulate in uterine and liver tissue due to reabsorption from the intestine after having been produced there from NIT and demethyl NIT, respectively. The effects of antiestrogens and their metabolites may be due in part to interaction with antiestrogen binding sites. Both demethyl KET and PMB had good affinity for such sites. Thus, these enteric bacterial metabolites not only have the ability to accumulate in vivo, but could, together with demethyl NIT, contribute to the antiestrogenic effects observed with NIT.

Substituted-vinyl hydroxytriarylethylenes, 1-[4-[2-(diethylamino) ethoxy]phenyl]-1-(4-hydroxyphenyl)-2-phenylethylenes: synthesis and effects on MCF 7 breast cancer cell proliferation.

A series of triarylethylene compounds related to 4-hydroxyclomiphene (2) in which the vinyl Cl substituent was replaced by ethyl (5), Br (6), H (7), CN (8), or NO2 (9) substituents were synthesized to facilitate studies of the molecular actions of synthetic nonsteroidal antiestrogens. The relative binding affinities of these compounds for the estrogen receptor (ER) and the antiestrogen binding site (AEBS) in MCF 7 human mammary carcinoma cells were measured and correlated with the effects of these drugs on cell proliferation kinetics. Affinities for ER and AEBS were highly correlated, illustrating that vinyl substituents influence binding to ER and AEBS in a parallel manner. All compounds except 7 had biphasic effects on cell proliferation kinetics, indicating the presence of at least two distinct mechanisms by which hydroxytriarylethylenes inhibit breast cancer cell proliferation. In the concentration range 10(-10)-10(-8) M, cell proliferation was inhibited by 60-70%, these effects were estrogen-reversible, and the degree of growth inhibition was in the order Cl greater than Et greater than Br greater than NO2 greater than CN greater than H, which paralleled the order of affinities for ER. There was no further inhibition of cell growth between 10(-8) and 10(-6) M, but at concentrations greater than 10(-6) M there was a further dose-dependent decrease in cell growth mediated by mechanisms yet to be defined but apparently distinct from ER-mediated events. In both concentration ranges, growth inhibition was accompanied by accumulation of cells in the G1 phase of the cell cycle. These data, obtained with a novel series of hydroxytriarylethylenes, have enabled clear definition of two distinct mechanisms of growth inhibition by triarylethylene antiestrogens. They also indicate that among the vinyl substitutions examined to date the Cl substituent yields the most active molecule both in terms of affinity for ER and AEBS and potency as a growth inhibitory agent.

Comparative fates of clomiphene and tamoxifen in the immature female rat.

The triarylethylene antiestrogens clomiphene (CLO) and tamoxifen (TAM) have each been shown to be converted in vitro to "active" metabolites which may contribute to their antiestrogenic effects. We have studied the disposition of CLO and TAM in the immature female rat, the animal model with which the majority of biochemical studies of the effects of antiestrogens have been conducted. Both drugs were eliminated mainly by the feces after ip administration, with CLO being eliminated three times as efficiently (57%) as TAM (19%) over 24 hr. Most of the dose of CLO was eliminated unchanged; most of the dose of TAM was eliminated as metabolites, especially 4-hydroxy-TAM. TAM was accompanied by an array of metabolites in liver and uterine tissues 24 hr after ip injection. In contrast, injection of CLO resulted in negligible recoveries from these tissues of metabolites demonstrated to be produced in the presence of liver microsomal homogenates. Instead, a polar material of unidentified composition accompanied unchanged CLO in these tissues. These results reconfirm the fact that the effects of TAM are due in part to its metabolites and suggest that, in contrast, the effects of CLO are due mainly to unchanged drug.

Structural requirements for the pharmacological activity of nonsteroidal antiestrogens in vitro.

The structure-activity relationships of a tamoxifen (TAM) (Z-1-(4- beta-dimethylaminoethoxyphenyl)1,2-diphenylbut-1-ene) series have been investigated. The tamoxifen derivatives were assayed in vitro by their modulation of estradiol (E2)-stimulated prolactin synthesis in primary cultures of dispersed rat pituitary gland cells. Monohydroxylation of TAM in position 4 of the stilbene ring system was found to be the optimal substitution for binding to the estrogen receptor [relative binding affinity (RBA) = 234] and to inhibit E2 (1 nM)-stimulated prolactin synthesis (IC50 7 nM) by pituitary cells in primary culture. Substitution in positions 3 and 4 to form a catechol did not decrease affinity for the estrogen receptor (RBA = 252), and potency as an antiestrogen was maintained in the prolactin assay (IC50 20 nM) as long as oxidation of the catechol was prevented. All of the hydroxylated derivatives of tamoxifen tested were estrogen antagonists; however, removal of the alkylaminoethoxy side chain from TAM produced a full estrogen agonist with low potency (20 nM). In contrast, removal of the side chain from 4-hydroxytamoxifen (4-OH TAM) produced a partial agonist. A structural analogue of 4-OH TAM, 3-[beta-dimethylaminoethoxy]-11-ethyl-12-(4-hydroxyphenyl)5,6- dihydrodibenzo[a,e]-cyclooctene (7c) had a decreased potency (IC50 16 nM) compared with 4-OH TAM (IC50 4 nM in the same experiment) as an estrogen antagonist. If the side chain was changed from a dimethylaminoethoxy to glyceryl, antagonist activity was reduced (IC50 0.8 microM). An allyl side chain produced a compound with no antiestrogenic activity at concentrations up to 1 microM. An adaptation of Belleau's macromolecular perturbation theory is suggested to explain the interaction of agonists, antagonists, and partial agonists at the ligand binding site of the estrogen receptor.

Some chemical and biochemical aspects of liver microsomal metabolism of tamoxifen.

The triarylethylene antiestrogen tamoxifen (TAM) has been shown to undergo N-demethylation, 4-hydroxylation, and N-oxidation in animals and man. We have studied the effects of drug metabolism inhibitors metyrapone and SKF 525-A, and an inducer (phenobarbital), on these processes and on overall TAM metabolism, in the presence of rat and rabbit liver microsomes. In the rabbit, metyrapone had no significant inhibitory effects. In the rat, it inhibited N-demethylation by 40% at a concentration of 1 microM, while overall TAM metabolism and 4-hydroxylation were unaffected. SKF 525-A markedly inhibited all of these processes in both species. Enzymatic N-oxidation of TAM in the rat was unaffected by either inhibitor, suggesting this to be independent of cytochrome P-450. In the rat, phenobarbital pretreatment increased N-demethylation by 105% and decreased 4-hydroxylation by 48% compared to corresponding rates in untreated animals. Together with the results obtained with the inhibitors, these findings implicate participation of alternative isoenzymatic forms of cytochrome P-450 in N-demethylation and 4-hydroxylation of TAM. In the rat, the sum of the amounts of the three metabolites found was less than the amount of TAM metabolized, implying the existence of additional biotransformation routes. Radiochromatographic analysis of extracts of incubation mixtures showed the presence of the three known metabolites, plus two additional ones. The more polar of these was spectrally and chromatographically identical to authentic 4'-hydroxytamoxifen. The other one, which was slightly less polar than TAM, was tentatively identified as TAM epoxide.

Estrogen receptor binding and estrogenic/antiestrogenic effects of two new metabolites of nitromiphene, 2-[p-[2-nitro-1-(4-methoxyphenyl)-2-phenylvinyl]phenoxy]-N-ethylpyrrolidine.

Reduction of the triarylethylene antiestrogen 2-[p-[2-nitro-1-(4-methoxphenyl)-2-phenylvinyl]phenoxy]-N-ethylpyrrolidine (1) with sodium borohydride-stannous chloride afforded 2-(p-methoxyphenyl)-p'-(2-pyrrolidin-1-ylethoxy)deoxybenzoin (2). Incubation of 1 with rat cecal content suspension under aerobic or anaerobic conditions also resulted in the generation of 2. The lactam analogue of 1 (6) was prepared by condensation of 4-(2-bromoethoxy)-4'-methoxybenzophenone (3) with benzylmagnesium chloride, followed by dehydration, amidation with 2-pyrrolidinone, and nitration. A metabolite with chromatographic and spectral properties identical with those of 6 was found in extracts from incubation mixtures of 1 with phenobarbital-induced rat liver 9000g supernatant. Compound 2 did not exhibit appreciable binding to the rat uterine cytosol estrogen receptor at concentrations of up to 1 X 10(-6) M and had no estrogenic or antiestrogenic activity in the 3-day rat uterotropic assay. By contrast, 6 had estrogen receptor affinity somewhat greater than that of 1 and slightly greater estrogenic activity accompanied by reduced antiestrogenic activity in comparison with those of 1.