Genetic determination of mortality rate in Danish dairy cows: A multivariate competing risk analysis based on the number of survived lactations.

Dairy cow mortality has been steadily increasing during the last 2 decades in Denmark. This study aims to verify whether genetic mechanisms might be contributing to this increase. To do so, the records of 880,480 Holstein, 142,306 Jersey, and 85,206 Red Danish dairy cows calving from 1990 to 2006 were retrieved from the Danish Cattle register. Two causes of culling of cows were considered: death and slaughtering. Bivariate competing risk genetic models with a sire model structure were used to describe the death and the slaughtering rates simultaneously. The models included 2 random components: a sire random component with pedigree representing the sire genetic effects and a herd-year-season component. Moreover, the level of heterozygosity and the sire breed proportions were included in the models as covariates to account for potential nonadditive genetic effects due to the massive introduction of genetic material from other populations. The correlations between the sire components for death rate and slaughter rate were negative and small for the 3 populations, suggesting the existence of specific genetic mechanisms for each culling reason and common concurrent genetic mechanisms. In the Holstein population, the effects of the changes in the level of heterozygosity, breed composition, and the increasing genetic trend acted in the same direction, increasing the death rate in recent years. In the Jersey population, the effects of the level of heterozygosity and the breed proportion were small, and only the increasing genetic trend can be pointed as a genetic cause to the observed increase in the mortality rate. In the Red Danish population, neither the time-development pattern of the genetic trend nor the changes in the level of heterozygosity and breed composition could be causing the observed increase in the mortality; thus, nongenetic factors must be causing this negative development.

Genetic parameters of the piglet mortality traits stillborn, weak at birth, starvation, crushing, and miscellaneous in crossbred pigs.

This study aimed to estimate genetic parameters for the mortality causes stillborn, weak at birth, starvation, crushing, and miscellaneous in crossbred piglets produced by crossbred dams. Data were collected in a single Danish commercial herd from October 2006 to July 2008 and consisted of 34,194 piglets (2,152 litters), which originated from 195 Danish Duroc sires and 955 crossbreds between Danish Landrace and Danish Yorkshire dams. Of the 34,194 piglets born, 11.5% were stillborn, 4.2% were crushed by the sow, 2.7% died due to starvation, 2.3% were weak at birth, and 2.2% died of miscellaneous causes before weaning. The first 4 mentioned causes were analyzed multivariately using a generalized linear mixed model with a probit link function, including the genetic effect of both sire and dam. Heritabilities based on the sire component ranged between 0.08 for stillborn and 0.21 for starvation whereas heritabilities based on the dam component ranged between 0.01 for miscellaneous and 0.24 for stillborn, indicating that reducing piglet mortality through genetic selection is possible. The expected observed responses to selection would, however, be low. The genetic correlations between mortality traits based on the sire component ranged from -0.05 between stillborn and starvation to 0.35 between stillborn and weak at birth whereas genetic correlations based on the dam component ranged from -0.11 between weak at birth and starvation to 0.76 between crushing and starvation. There seemed to be a favorable relationship between the 2 traits stillborn and weak at birth and between crushing and starvation, implying that care should be taken with correct recordings of mortality causes. The genetic correlation precision was rather low, and if nonadditive effects are not accounted for, there may be unexpected correlated responses among the different mortality causes in the crossbred mortalities.

Genetic variation of contact dermatitis in broilers.

This study aimed to investigate the presence of genetic variation in footpad dermatitis (FPD) and hock burns (HB) and the possibility to genetically select against these. A field trial including 10 commercial broiler lines (n = 102 to 265) was carried out at 2 Dutch farms. Footpad dermatitis and HB were subjectively scored at approximately 4, 5, and 7 wk on a scale from 0 through 5. Genetic parameters were estimated in 2 lines based on a larger data set. The overall agreement of repeated FPD and HB scores was high (0.66 to 0.86) and the scoring system was, therefore, considered reliable. Kendall's tau between left and right scores was lower than 1 (FPD: 0.73 and HB: 0.57), and both left and right FPD and HB must, therefore, be evaluated. High prevalences of FPD, but also HB, were achieved in the field trial, but lower prevalences may be sufficient for genetic evaluations and would be less detrimental to welfare. Genetic variation between and within lines was present for both FPD and HB as indicated by between-line differences and heritabilities, and selection against FPD and HB is, therefore, possible. It is important that selection is done against both FPD and HB, and such selection should not have a negative influence on the genetic improvement in BW. In contrast, continued selection for increased BW while ignoring FPD in the breeding goal is likely to lead to an increased propensity to develop FPD in broilers.

Genetic parameters for oocyte number and embryo production within a bovine ovum pick-up-in vitro production embryo-production program.

Genetic factors influencing the outcome of bovine ovum pick-up-in vitro production (OPU-IVP) and its relation to female fertility were investigated. For the first time, genetic parameters were estimated for the number of cumulus-oocyte complexes (Ncoc), quality of cumulus-oocyte complexes (Qcoc), number and proportion of cleaved embryos at Day 4 (Ncleav(D4), Pcleav(D4)), and number and proportion of total and transferable embryos at Day 7 of culture (Nemb(D7), Pemb(D7) and NTemb(D7), PTemb(D7), respectively). Data were recorded by CRV (formally Holland Genetics) from the OPU-IVP program from January 1995 to March 2006. Data were collected from 1508 Holstein female donors, both cows and pregnant virgin heifers, with a total of 18,702 OPU sessions. Data were analyzed with repeated-measure sire models with permanent environment effect using ASREML (Holstein Friesian). Estimates of heritability were 0.25 for Ncoc, 0.09 for Qcoc, 0.19 for Ncleav(D4), 0.21 for Nemb(D7), 0.16 for NTemb(D7), 0.07 for Pcleav(D4), 0.12 for Pemb(D7), and 0.10 for PTemb(D7). Genetic correlation between Ncoc and Qcoc was close to zero, whereas genetic correlations between Ncoc and the number of embryos were positive and moderate to high for Nemb(D7) (0.47), NTemb(D7) (0.52), and Ncleav(D4) (0.85). Genetic correlations between Ncoc and percentages of embryos (Pcleav(D4), Pemb(D7), and PTemb(D7)) were all close to zero. Phenotypic correlations were in line with genetic correlations. Genetic and phenotypic correlations between Qcoc and all other traits were not significant except for the phenotypic correlations between Qcoc and number of embryos, which were negative and low to moderate for Nemb(D7) (-0.20), NTemb(D7) (-0.24), and Ncleav(D4) (-0.43). Results suggest that cumulus-oocyte complex (COC) quality, based on cumulus investment, is independent from the total number of COCs collected via OPU and that in general, a higher number of COCs will lead to a higher number of embryos produced. The correlation between the estimated breeding values for Ncoc and PTemb(D7) of sires in this study and the sires breeding index for female-fertility based on the Dutch cattle population was close to zero. This study revealed OPU-IVP traits (Nemb(D7), NTemb(D7), and Ncoc) that could be of potential value for selection. Introduction of such traits in breeding programs would enhance the number of offspring from superior donors as well as improve the cost efficiency of OPU-IVP programs.

Modeling variability in immunocompetence and immunoresponsiveness.

The purposes of this paper were to 1) develop a stochastic model that would reflect observed variation between animals and across ages in immunocompetence and responsiveness; and 2) illustrate consequences of this variability for the statistical power of genotype comparisons and selection. A stochastic model of immunocompetence development and responsiveness kinetics was developed. This model enabled variability in immunological variables to be taken into account in the evaluation of challenge and measurement strategies for selection. The characteristics of the variation in model output reflect those observed in the literature, to the extent that variation in the literature shows a consistent pattern; knowledge of true variation and patterns of variation in immunological variables is limited. The model created correlations between immunocompetence and immunoresponsiveness components, as well as correlations within each component across time. These correlations were generally in agreement with literature estimates, where available. The model enabled predictions of the effectiveness of selection for improved health through immunocompetence or immunoresponsiveness. It was predicted that effective selection for increased general immunocompetence to improve health should be done only when baseline immunity has matured. Further, the model implied that selection is unlikely to be successful if it is based only on a single measurement. Problems with low statistical power to detect differences between genotypes can be reduced by increasing challenge age in the experimental design, and one should ensure that the effects of maternal immunity are minimal when the challenge is done. The ability to detect differences between different groups of animals differs substantially with measurement timing because of low repeatabilities of immunocompetence and responsiveness across time. In general, the probability of detecting differences becomes higher when the challenge age is increased. Consequently, both the age at selection and the age at which information is gathered for selection must be considered carefully when designing genetic evaluations.

Modeling immunocompetence development and immunoresponsiveness to challenge in chicks.

The purpose of this study was 2-fold: 1) to develop a deterministic model that describes the development of immunocompetence and the kinetics of immunoresponsiveness to a pathogenic challenge in chicks and 2) to use this model to illustrate the importance of factors in experimental design, such as type of variable measured, measurement timing, and challenge age. Difficulties in evaluating immunological variables hinder attempts to improve animal health through selection on immunological variables. In young chicks, evaluating immunological variables is additionally complicated by immune system development and maternal immunity. The evaluation of immunocompetence and immunoresponsiveness and the definition of appropriate challenge and measurement strategies may be enabled through a mathematical model that captures the key components of the immune system and its development. Therefore, a model was developed that describes the development of immunocompetence as well as the kinetics of immunoresponsiveness to a pathogenic extracellular bacterial challenge in an individual chick from 0 to 56 d of age. The model consisted of 4 components describing immunocompetence (maternal and baseline immunity) and immunoresponsiveness (acute phase and antibody response). Individual component equations generally fit published data adequately. Four scenarios that represented combinations of challenge age and measurement timing were simulated. In each scenario, the immunoresponsiveness to a particular challenge was compared for 3 different levels of baseline immunity, representing 3 broiler genotypes. It was illustrated that experimental design (type of immunoresponsiveness measured, measurement timing, and challenge age) can have an important effect on the ranking of genotypes, groups, or individuals and on the reliability of extrapolations based on this ranking. It is concluded that this model is a potentially useful tool in the definition of appropriate challenge and measurement strategies when evaluating immunocompetence and immunoresponsiveness. Further, it may be used as a generator of hypotheses on global immunological relationships to be tested experimentally.

Role of thyroid hormones, maternal antibodies, and antibody response in the susceptibility to colibacillosis of broiler genotypes.

The purpose of this study was to investigate whether differences in susceptibility to colibacillosis are associated with maternal antibodies, antibody response, and alterations in thyroid hormones [triiodothyronine (T3) and thyroxine (T4)] and to investigate the effect of genotype on the changes in T3 and T4 during challenge and antibody response. A challenge experiment was executed in 2 trials. Per trial, 24 chicks per genotype were challenged, and 20 chicks per genotype were controls. At 7 d of age, challenged chicks were intratracheally inoculated with 0.3 mL of Escherichia coli O78K80 and controls with 0.3 mL of PBS. All chicks were euthanized at 14 or 15 d. Thyroid hormone plasma concentrations and E. coli-specific antibody titers (AB) were measured at 7 d (T(3 d7), T(4 d7), and AB(d7)) and 14 or 15 d (change from 7 to 14 or 15 d was analyzed: DeltaT(3), DeltaT(4), and DeltaAB). Susceptibility was defined based on mortality, lesions, growth retardation, and eating behavior. There was a significant effect of challenge on T(3 d7); probably due to eating pattern in association with circadian rhythm. The challenge group was suggested to have functional hypothyroidism relative to the control group, indicating metabolic changes due to the challenge, and it was indicated that an antibody response was elicited. Differences in susceptibility were not significantly related to differences in T(3 d7), T(4 d7), DeltaT(3), or DeltaT(4) or to maternal antibodies (AB(d7)), but the antibody response tended to increase (decreasing DeltaAB) with increasing susceptibility. There were indications of genetic variation in T(4 d7), DeltaT(4), AB(d7), and DeltaAB, but there was no observed effect of genotype on DeltaT(3) and DeltaT(4) during challenge or on the antibody response. Further, there were indications that selection for growth traits has resulted in alterations in DeltaT(4) due to challenge, as indicated by a lower DeltaT(4) in the challenge group relative to the control group for more intensively selected genotypes as opposed to a higher DeltaT(4) for less intensively selected genotypes.

Defining susceptibility of broiler chicks to colibacillosis.

This study aimed to define the susceptibility of broilers to colibacillosis through quantification of clinical responses and to examine the relationship between susceptibility and growth retardation. A challenge experiment was carried out twice. In each trial, 192 chicks were challenged intratracheally with Escherichia coli (E. coli) at 7 days of age and 160 chicks served as controls. Surviving chicks were euthanized at 14 or 15 days. Parameters measured were: daily mortality, lesion scores, body weight at 1, 4, 7, 10, 12 and 14 or 15 days and feeding behaviour at 6, 11 and 13 days. The results were reproducible, and increasing susceptibility to colibacillosis was defined by four categories: chicks without lesions, chicks with airsacculitis but no systemic lesions, chicks with systemic lesions, and chicks that die. Increasing susceptibility was associated with increasing growth retardation, but growth retardation was not inevitably linked to challenge with E. coli.

Genetic variation among broiler genotypes in susceptibility to colibacillosis.

Selection for reduced susceptibility to colibacillosis in broilers may contribute to the prevention of colibacillosis. Such selection should focus on the responses to Escherichia coli rather than the associated primary agent(s). The purpose of the current study was to examine whether genetic variation is present in the susceptibility to colibacillosis. This was achieved through an evaluation of the susceptibility to primary colibacillosis in 5 pure broiler lines, a slow-growing line, and two 2-way crosses of the pure lines (altogether referred to as genotypes). A challenge experiment was executed in 2 trials. Per trial, 24 chicks per genotype were challenged and 20 chicks per genotype were controls. At 7 d of age, challenged chicks were intratracheally inoculated with 0.3 mL of E. coli O78K80 solution, and controls with 0.3 mL of PBS. All chicks were euthanized at 14 or 15 d. Traits measured were mortality, lesion scores (airsacculitis, pericarditis, and perihepatitis) at 14 or 15 d, and BW at 1, 4, 7, 10, 12, and 14 or 15 d. An effect of genotype on mortality, lesion prevalence, and growth retardation was found, indicating the presence of genetic variation in susceptibility to colibacillosis, and suggesting that selection for reduced susceptibility is possible. There were large between-genotype differences in mortality (up to 46%) and in lesion prevalence (up to 41%). Growth retardation was not observed for any genotype in chicks without lesions, whereas genotypes differed from none to 20% growth retardation for chicks with airsacculitis but no systemic lesions, and up to 13% for chicks with systemic lesions. The heterosis in susceptibility and growth retardation was found to be either negative or absent, indicating that crossbreeding would not be an advantage for the selection for reduced susceptibility, and that test crossing is essential.

Genetic and phenotypic correlations between feather pecking and open-field response in laying hens at two different ages.

The object of this research was to study the relationship between feather pecking and open-field activity in laying hens at two different ages. A population of 550 birds of a laying hen cross was subjected to an open-field test at 5 and 29 weeks of age and to a social feather pecking test at 6 and 30 weeks of age. Factor analysis was used to identify underlying factors for each test: pecking behavior (social test) and open-field activity (open-field test). In young birds, a positive phenotypic correlation of 0.24 was found between high open-field activity and high levels of pecking behavior (ground pecking, preening, gentle feather pecking, and wall pecking). In adults, a similar genetic correlation of 0.62 was found. At adult age, the factor pecking behavior consisted mainly of gentle and severe feather pecking. Between ages, a strong, negative genetic correlation of -0.65 was found between open-field activity at young age and pecking behavior at adult age, indicating that open-field activity levels in young birds may predict pecking behavior in adult hens.

Heritability of feather pecking and open-field response of laying hens at two different ages.

The objective of the current study was to estimate heritabilities (h2) of feather pecking and open-field response of laying hens at two different ages. An F2 cross, originating from a high and a low feather pecking line of laying hens, was used for the experiment. Each of the 630 birds of the F2 cross was subjected to an open-field test (individual, 10 min) at 5 and 29 wk of age and to a social feather pecking test (groups of five birds on wood shavings, 30 min) at 6 and 30 wk of age. Both tests were performed in a square open field (1.25 x 1.25 m). Behavior was recorded directly from a monitor. Heritabilities of feather pecking and open-field behaviors were calculated. In the open-field test at 5 wk of age, high h2 were found for most traits, ranging from 0.20 for the frequency of flying to 0.49 for number of steps. In the social test at 6 wk, gentle feather pecking (0.12) and ground pecking (0.13) were found to be heritable. When both tests were repeated at 29 and 30 wk of age, h2 estimates were lower for the open-field test, ranging from 0.10 for duration of sitting to 0.20 for latency to first step. In the social test, however, higher h2 estimates of 0.15 for gentle feather pecking and 0.30 for ground pecking were found compared with 6 wk of age. In conclusion, gentle feather pecking and open-field behaviors may be used in selection against feather pecking.

Intra-individual variation and sex differences in gene expression of cytochromes P450 in circulating leukocytes.

To clarify partly inconsistent results in gene expression of cytochromes P450 (CYP) in the circulation, we undertook a systematic study over a long time period in 19 healthy men and women. CYP specific mRNA for 1A2, 1B1, 2E1 and 3A4 was studied in the leukocytes collected repeatedly on 20 occasions over a 10-week period. Our study revealed a varying pattern of CYP expression over time. CYP3A4 specific mRNA exhibited the largest intra-individual variation with an average coefficient of variation between 40 and 250%. CYP1B1 and CYP2E1 did not vary as much (39-110%). CYP1A2 was sporadically detected in only ten individuals, but varied considerably when measurable (61-256%). The expression in CYP1B1 was significantly higher in women than in men (P = 0.02). We conclude that CYP gene expression in blood varies considerably over time. It is conceivable that the variation reflects a hitherto unknown influence of exogenous or endogenous factors such as hormones, cytokines, and other circulating factors on the hematogeneous cytochromes.

Messenger ribonucleic acid levels of steroid 5 alpha-reductase 2 in human prostate predict the enzyme activity.

Testosterone is converted to dihydrotestosterone by 5 alpha-reductase2 in the prostate. Dihydrotestosterone controls cell division, and interindividual differences in prostatic 5 alpha-reductase 2 expression and activity may be a determinant of the risk of developing prostate cancer. However, little is known about interindividual differences in intraprostatic hormonal activity in vivo. To determine whether 5 alpha-reductase-specific messenger RNA (mRNA) is predictive of 5 alpha-reductase activity in prostatic tissue, we analyzed 30 prostatic tissue specimens from 15 Caucasian patients, 47--82 yr old. The mRNA was measured by RT-PCR. Five specimens consisted of cancer, whereas the remaining 25 were derived from benign prostate hyperplasia (BPH). We found a strong association between enzyme activity at pH 5.5 and the 5 alpha-reductase 2-specific mRNA expression when expressed on the basis of beta-actin [Spearman's rank-correlation coefficient (r(s)) = 0.81; 95% confidence interval, 0.64-0.91; P < 0.0001]. The expression of 5 alpha-reductase 2-specific mRNA in the cancer specimens was significantly lower than in the BPH tissue (P = 0.03). There was no difference in the expression of 5 alpha-reductase 1-specific mRNA in the cancer specimens, compared with BPH (P = 0.56). The strong association between 5 alpha-reductase activity at pH 5.5 and the 5 alpha-reductase 2-specific mRNA expression makes it possible to predict prostatic 5 alpha-reductase activity using core needle biopsies.

Insulin-like growth factor 1 (IGF-I) effects on sex-specific cytochrome P450 enzymes in normal and hypophysectomised male rats.

The role of growth hormone (GH) in the regulation of the sex-differentiated rat cytochrome P450 (CYP) enzymes has been extensively studied. However, little is known about the involvement of insulin-like growth factor I (IGF-I) as a mediator in this regulation. We wanted to study if IGF-I had effects on sex-differentiated CYP enzymes and to compare the effects of IGF-I to the effects of GH. IGF-I, GH or saline was administered continuously via osmotic minipumps to normal and hypophysectomised rats for seven days. After treatment, the expression of several sex-differentiated liver enzymes (CYP2C11, CYP2C12), the female-dominant steroid 5alpha-reductase, and the male-dominant CYP3A2 enzyme was studied at mRNA, protein and/or functional levels. Our results demonstrate that IGF-I has marked effects on the sex-specific expression of CYP2C11 and CYP2C12. The effects of IGF-I were similar to those of GH. In contrast, in hypophysectomised rats IGF-I gave effects opposite to those observed after GH treatment to normal rats on the CYP3A-associated cortisol 6beta-hydroxylation. No effects of IGF-I on the steroid 5alpha-reductase activity were observed.

Tricyclic antidepressants inhibit opioid receptor binding in human brain and hepatic morphine glucuronidation.

The opioid receptor binding in the human thalamic area was studied with U-69593 and naloxone as ligands for the kappa and mu receptors, respectively. The binding was inhibited by various tricyclic antidepressants including amitriptyline, nortriptyline, clomipramine and fluoxetine. The antidepressants tested had a slight selectivity for the kappa receptor type. The IC50-values for all tricyclic antidepressants tested were in the 10(-6) M concentration range. Morphine and tricyclic antidepressants are substrates of a liver microsomal uridine diphosphate glucuronyl transferase (UDPGT). The interaction of the tricyclic antidepressants with morphine glucuronidation was investigated in human liver microsomal preparations. All drugs inhibited the morphine UDPGT. In Dixon plots inhibition of the formation of morphine-3-glucuronide and morphine-6-glucuronide was non-competitive for nortriptyline, and competitive or mixed for amitriptyline and clomipramine. Lubrol PX activated the morphine-UDPGT four to five times. The degree of activation of the enzyme(s) was unaltered in presence of the inhibiting drugs. The inhibition was also observed at a tricyclic antidepressant/morphine concentration ratio close to that achieved in plasma from patients treated with these drugs.

Comparison of human fetal hepatic and adrenal cytochrome P450 activities with some major gestational steroids and ethylmorphine as substrates.

The immunoidentified human fetal liver and adrenal microsomal contents of cytochromes P450IIIA and P450XVIIA1 were compared to the metabolism of steroids and ethylmorphine. In fetal liver microsomes, 16 alpha-hydroxylation of dehydroepiandrosterone (DHA) was catalyzed at a high rate in almost all investigated specimens and accompanied by a high ethylmorphine N-demethylase activity. Progesterone 16 alpha- and 17 alpha-hydroxylation was found only in the livers with the highest DHA 16 alpha-hydroxylation activities, while 21-hydroxylation of progesterone was catalyzed only occasionally in these samples. In fetal adrenal microsomes, 21-hydroxylation of progesterone to 11-desoxycorticosterone (DOC) and 11-desoxycortisol (DOCOL) was catalyzed. In contrast to fetal liver, the adrenals also catalyzed the 17 alpha-hydroxylation of pregnenolone and the formation of DHA from 17 alpha-OH-pregnenolone. 16 alpha-hydroxylation of DHA and ethylmorphine N-demethylation were modest in the adrenals. P450IIIA/HLp was immunoidentified in all investigated liver specimens except two (18/20) in which no ethylmorphine N-demethylation or 16 alpha-hydroxylation of DHA was found. P450XVIIA1 bands were observed in 8/20 blots of liver specimens, but there was no correlation between the density of these bands and the 17 alpha-hydroxylation of progesterone. All 11 fetal adrenal samples catalyzed DHA 16 alpha-hydroxylation, although only 8 were positive for P450IIIA/HLp. All investigated adrenals were positive in regard of the P450XVIIA1 band, except one (8/9) with a low 17 alpha-hydroxylation of progesterone. All adrenal specimens catalyzed 21-hydroxylation of progesterone and contained P450C21 bands in immunoblots and all samples catalyzed the formation of DOC and DOCOL from progesterone. Our findings in the fetal livers show a correlation between the DHA 16 alpha-hydroxylation and immunoidentified P450IIIA/HLp bands. In adrenals, there was a correlation between the immunoidentified P450XVIIA1 bands and the 17 alpha-hydroxylation of progesterone.

A conspicuous down-regulating effect of morphine on essential steroid hydroxylation reactions and certain drug N-demethylations.

This study was conducted to explore the potency of morphine to induce reductions of specific cytochrome P450 isoenzyme functions. Male Sprague-Dawley rats were treated with escalating doses (20-125 mg/kg per day) of morphine for 2 weeks in order to study the effects on the following cytochrome P450 catalyzed reactions: 16 alpha-hydroxylation of dehydroepienderosterone (DHA) and progesterone; 17 alpha- and 21-hydroxylation of progesterone; N-demethylation of ethymorphine, codeine and morphine as well as O-dealkylation of ethylmorphine and codeine. 16 alpha-Hydroxylation of DHA and progesterone and 17 alpha-hydroxylation of progesterone decreased to 18, 12 and 10% of control activities, respectively. The N-demethylation of ethylmorphine and codeine decreased to 34 and 43% of control activities, respectively. Morphine treatment had no effect on the 21-hydroxylation reactions or the O-dealkylation of ethylmorphine or codeine. A monoclonal antibody (Mab) against rat liver cytochrome P450 2 c/RLM 5 exerted a 66-73% inhibition of the N-demethylation of ethylmorphine and codeine, respectively, whereas the O-dealkylation reactions were not affected. This Mab inhibited the 16 alpha- and 17 alpha-hydroxylation of DHA and progesterone, whereas the 21-hydroxylation reactions were unaffected. The steroid hydroxylation reactions in rat adrenals were not altered upon morphine treatment. Our data suggest that a major part of the 16 alpha- and 17 alpha-steroid hydroxylations are catalyzed by the same (or closely related) cytochrome(s) P450 as the opioid N-demethylation reactions.

The enantioselective glucuronidation of morphine in rats and humans. Evidence for the involvement of more than one UDP-glucuronosyltransferase isoenzyme.

The formation of morphine glucuronides is enantio- and regioselective in rats and humans. In rat liver microsomes, natural (-)-morphine formed only the 3-O-glucuronide, whereas the unnatural (+)-morphine formed glucuronides at both the 3-OH and 6-OH positions, with the 6-O-glucuronide being the principal product. In human liver microsomes, both the 3-OH-and 6-OH positions were glucuronidated with each of the enantiomers, with the 3-O-glucuronide being the major product with (-)-morphine, and the 6-OH position preferred with the (+)-enantiomer. By using a series of biochemical and biological situations such as induction by xenobiotics, ontogeny, selective inhibition and genetic deficiencies, which are considered to be diagnostic of UDP-glucuronosyltransferase heterogeneity, we determined that two UDP-glucuronosyltransferase isoenzymes were responsible for the glucuronidation of morphine in rat liver. One isoenzyme (the so-called "morphine UDP-glucuronosyltransferase") was responsible for the glucoronidation at the (-)-3-OH and (+)-6-OH positions of morphine, whereas the other formed only the (+)-morphine-3-glucuronide. Evidence from enzyme induction and the genetically deficient deficient Gunn rat suggested that bilirubin UDPGT may be responsible for the (+)-morphine-3-UDP-glucuronosyltransferase activity. In human kidney, glucuronidation of both (-)- and (+)-enantiomers at the 6-OH position was deficient, whereas the activity at the 3-OH positions was still present, which indicated the involvement of two UDP-glucuronosyltransferases in the glucuronidation of morphine in man, as well as rats.