6-Mercaptopurine treatment of pregnant mice: effects on second and third generations

Management of acute and recurrent pericarditis in pregnancy

This review summarizes the currently available evidence on the management of acute and recurrent pericarditis during pregnancy, focusing on the safety of diagnostic procedures and treatment options for the mother and foetus. Family planning should be addressed in women with recurrent pericarditis of reproductive age and adjustment of therapy should be considered before a planned pregnancy. The treatment of pericarditis in pregnancy is similar to that for non-pregnant women but considers current knowledge on drug safety during pregnancy and lactation. The largest case series on this topic described 21 pregnancies with idiopathic recurrent pericarditis. Pregnancy should be planned in a phase of disease quiescence. Non-steroidal anti-inflammatory drugs can be used at high dosages until the 20th week of gestation (except low-dose aspirin 100 mg/die). Colchicine is allowed until gravindex positivity; after this period, administration of this drug during pregnancy and lactation should be discussed with the mother if its use is important to control recurrent pericarditis. Prednisone is safe if used at low-medium doses (2,5 - 10 mg/die). General outcomes of pregnancy in patients with pericarditis are good when the mothers are followed by a multidisciplinary team with experience in the field.

Maternal, foetal and child consequences of immunosuppressive drugs during pregnancy in women with organ transplant: a review

Although pregnancy remains exceptional in women after heart, liver or lung transplant, obstetricians and nephrologists are regularly confronted with pregnancy in renal transplant recipients. National and international registries have described the epidemiology of maternal, foetal and neonatal complications, and transplantation societies have published recommendations on the monitoring of these high-risk pregnancies. In this review, we summarize the existing data on maternal and foetal complications of pregnancies in women after renal transplant, especially the management of immunosuppression. We also describe the few available data on the middle- and long-term outcomes of their children who were exposed in utero to immunosuppressive drugs.

Problems Associated with Pregnancy in Renal Allograft Recipients

Of 18 pregnancies in 11 renal transplant recipients, three were terminated and in the remaining 15 (in 8 women) there were 10 live births (including one set of twins), five intrauterine deaths, and one spontaneous abortion. Graft function deteriorated in six women, from obstruction of the transplanted ureter in two, recurrent glomerulonephritis in two, rejection in one, and pelvi-ureteric junction obstruction in one. Hypertension worsened or developed in all but one of the pregnancies and proteinuria appeared in eight. Of the 10 live births only one reached 38 weeks gestation (mean 35 weeks) and four neonates were small for gestational age. One infant died early from intraventricular hemorrhage and hyaline membrane disease, one fetus had hydrocephalus, and the others were normal. Factors associated with a poor fetal outcome were deterioration in graft function during pregnancy, pre-existing hypertension, or the development of hypertension before the third trimester

Anti-inflammatory and immunosuppressive drugs and reproduction

Rheumatic diseases in women of childbearing years may necessitate drug treatment during a pregnancy, to control maternal disease activity and to ensure a successful pregnancy outcome. This survey is based on a consensus workshop of international experts discussing effects of anti-inflammatory, immunosuppressive and biological drugs during pregnancy and lactation. In addition, effects of these drugs on male and female fertility and possible long-term effects on infants exposed to drugs antenatally are discussed where data were available. Recommendations for drug treatment during pregnancy and lactation are given.

Complications of pregnancy and child development after cessation of treatment with 6-mercaptopurine for inflammatory bowel disease

PURPOSE

6-Mercaptopurine (6-MP) has proven efficacy in the therapy of inflammatory bowel disease. Its teratogenicity is demonstrated in animal studies when used at very high doses, whereas human data suggest that 6-MP at maintenance doses is safe. We report the outcome of 72 pregnancies in patients with inflammatory bowel disease who were previously treated with 6-MP with three different doses of 50, 75, and 100 mg/d, for a median duration of 18 months, along with long-term follow-up of the children.

METHODS

We have compared the outcome of pregnancies and development of the offspring in the following two groups: group 1, patients with inflammatory bowel disease who conceived 6 months to 22 years after stopping 6-MP (median 72 months); and group 2, patients with inflammatory bowel disease who never received 6-MP prior to conception. All pregnancies were evaluated in terms of outcome: live full-term birth, premature delivery, stillbirth, spontaneous abortion, ectopic pregnancy, and therapeutic dilatation and curettage. Data on children were obtained regarding birth weight, congenital anomalies, and development.

RESULTS

Group 1 included 72 pregnancies carried by 29 women. There were 51 live births (4 premature), 16 spontaneous abortions, 1 stillbirth, 2 therapeutic abortions due to abnormal amniocentesis, and 2 ectopic pregnancies. The total incidence of fetal loss was 29.2%. In group 2, 75 women had 140 pregnancies resulting in 120 live births (8 premature), 18 spontaneous abortions, and 2 stillbirths. There were no cases of ectopic pregnancies or abnormal amniocentesis. The total incidence of fetal loss was 14.3%. There was no increase in the incidence of developmental defects when the mothers had been treated with 6-MP prior to pregnancy.

CONCLUSIONS

The incidence of fetal loss is higher in women with inflammatory bowel disease who had been previously treated with 6-MP compared with those who had not. Whether this was related to the older age at conception in 6-MP group, longer duration of disease, initially more severe disease, or use of 6-MP we cannot tell.

Risks to the children born to mothers with autoimmune diseases

This article reviews current information regarding the development and long-term effects on children born to women with connective tissue diseases. There are few data on specific effects attributed to the underlying maternal disease, but fetal growth restriction and preterm birth are relatively common. Antenatal use of prednisone as treatment for these disorders appears to be safe, and most children have developed normally. However, there is growing concern that prolonged fetal exposure to other glucocorticoids such as dexamethasone or betamethasone may lead to decreased growth and abnormal neuronal development. Low birth weight is reportedly associated with long-term medical complications such as adult-onset hypertension. Evidence also suggests that immunosuppressive agents taken during pregnancy might predispose the progeny to autoimmune disorders, malignancies and reproductive problems. Further research is warranted to determine that there are no unrecognized long-term risks to the offspring of these women.

Pregnancy in renal transplant recipients

Most women of childbearing age who receive a renal transplant have a return of normal menses and have the ability to become pregnant. Most studies indicate that pregnancy does not adversely affect the transplant kidney's survival as long as renal function is good and serum creatinine is stable before pregnancy. The experience with immunosuppressive drugs has been surprisingly reassuring with no increase in congenital anomalies with cyclosporine, prednisone, and azathioprine. There is little experience with newer drugs. Pregnant transplant recipients need to be monitored for opportunistic infections, which may adversely affect the fetus, including herpes, toxoplasmosis, and CMV. Hypertension, urinary tract infections, and anemia are other common problems in pregnant transplant recipients. Despite a high frequency of premature births, over 80% of pregnancies result in surviving infants.

Autoimmune and pregnancy complications in the daughter of a kidney transplant patient

BACKGROUND

Immunosuppressive agents taken by pregnant organ transplant recipients readily cross the placenta during development of the fetal immune system. There are few data on the long-term implications for the progeny, but evidence from animal studies suggest that second and third generations of organ transplant patients may be at risk for autoimmune disorders and reproductive problems.

METHODS

We present the 23-year-old daughter of a renal allograft recipient exposed to azathioprine 75 mg/day and prednisone 5 mg/day throughout her mother's pregnancy.

RESULTS

During the daughter's first pregnancy, she developed multiple autoantibodies, Raynaud's phenomenon, and fetal death occurred at 20 weeks gestation. The second pregnancy was complicated by systemic lupus erythematosus, preeclampsia, and the birth of a preterm male infant.

CONCLUSIONS

It is uncertain whether the autoimmune manifestations and obstetric complications in this patient were related to fetal exposure to immunosuppressive drugs. Nevertheless, further studies on the health and pregnancies of adult offspring of transplant patients are warranted.

Drugs in pregnancy. Renal disease

The management of pregnant women with renal impairment presents a major challenge to obstetricians, nephrologists, and ultimately paediatricians. As renal failure progresses there is an increase in both maternal and fetal complications. Often these women have intercurrent medical conditions and, prior to conception, are receiving a broad range of prescribed medications. A successful obstetric outcome relies upon careful pre-pregnancy counselling and planning, obsessive monitoring during pregnancy, and close liaison between different specialist teams. Experience is mounting in the management of pregnant transplant recipients, but the introduction of newer immunosuppressive agents which have great promise in prolonging graft survival present new problems for those recipients of a kidney transplant who are planning to conceive. We review drug prescription for pregnant patients with renal impairment, end-stage renal failure, or a kidney transplant.

Treating inflammatory bowel disease during pregnancy: risks and safety of drug therapy

The safety of drug therapy for inflammatory bowel disease during pregnancy is an important clinical concern. Current available information is largely derived from animal studies and clinical experience among patients with inflammatory bowel disease and autoimmune disorders and organ transplant recipients. However, these data are confounded by various factors including difficulty projecting the results of animal studies to humans, methodological deficiencies of some studies, insufficient experience with certain agents, difficulty distinguishing the fetal effects of underlying disease from drug therapy and a need to consider the impact of background rates of adverse fetal outcomes which apply to all pregnancies. In inflammatory bowel disease, the effects of active inflammation on the fetus are believed to be more harmful than those of drug treatment, and therapy is often justified to induce or maintain remission during pregnancy. The choice of appropriate treatment is determined by the severity of the disease and the potential for drug toxicity. No causal relationship has been established between exposure to sulfasalazine or other 5-aminosalicylic acid drugs and the development of congenital malformations. These drugs may be used with relative safety during pregnancy and lactation. Considerable experience with corticosteroids have shown them to pose very small risk to the developing fetus. Current evidence indicates that maternal use of azathioprine is not associated with an increased risk of congenital malformations, though impaired fetal immunity, growth retardation or prematurity is occasionally observed. Preliminary evidence derived from patients with inflammatory bowel disease show no significant fetal toxicity following first trimester exposure to mercaptopurine, though its elective use in pregnancy is controversial. Cyclosporin is not teratogenic, but may be associated with growth retardation and prematurity. Pregnancy should be avoided in women treated with methotrexate because of its known abortifacient effects and risk of causing typical malformations. Although treatment with metronidazole or ciprofloxacin for short durations appear to be devoid of adverse fetal reactions, the effect of prolonged exposure as required in Crohn's disease remains unknown.

Pregnancy in chronic renal insufficiency and end-stage renal disease

Childbearing is important to women with renal disease, but pregnancy has generally been regarded as very high risk in these women. In this review, an attempt is made to clarify the nature and severity of those risks in the settings of chronic renal insufficiency and end-stage renal disease, including dialysis patients and transplant recipients. Hypertension is the most common life-threatening problem in all three groups. A wide range of antihypertensive medications have been used, with angiotensin-converting enzyme inhibitors the only drugs absolutely contraindicated because of their association with neonatal anuria, pulmonary hypoplasia, and neonatal death. Women with serum creatinine levels of 1.4 mg/dL or greater are at risk for accelerated loss of renal function compared with women who don't become pregnant. Transplant recipients have a risk for loss of renal function similar to controls as long as renal function is well preserved. The frequency of conception is decreased in women with renal insufficiency and markedly decreased in dialysis patients (0.5% per year). Return of fertility is the rule in transplant recipients. Exposure to immunosuppressive drugs, including prednisone, azathioprine, cyclosporine, and tacrolimus, has not been associated with an increase in congenital anomalies. These drugs, particularly cyclosporine, have been associated with small-for-gestational-age babies. Transplant recipients are at risk for infections that have implications for the fetus, including cytomegalovirus, herpes simplex, and toxoplasmosis. All groups have an increased risk for prematurity and intrauterine growth restriction. The percentage of pregnancies resulting in surviving infants in women with renal insufficiency and transplant recipients ranges from 70% to 100%. For women who conceive after starting dialysis, the likelihood of a surviving infant is approximately 50%.

Drug safety issues in pregnancy following transplantation and immunosuppression: effects and outcomes

Successful pregnancy outcomes are possible after solid organ transplantation. While there are risks to mother and fetus, there has not been an increased incidence of malformations noted in the newborn of the transplant recipient. It is essential that there is closely coordinated care that involves the transplant team and an obstetrician in order to obtain a favourable outcome. Current data from the literature, as well as from reports from the National Transplantation Pregnancy Registry (NTPR), support the concept that immunosuppression be maintained at appropriate levels during pregnancy. At present, most immunosuppressive maintenance regimens include combination therapy, usually cyclosporin or tacrolimus based. Most female transplant recipients will be receiving maintenance therapy prior to and during pregnancy. For some agents, including monoclonal antibodies and mycophenolate mofetil, there is either no animal reproductive information or there are concerns about reproductive safety. The optimal (lowest risk) transplant recipient can be defined by pre-conception criteria which include good transplant graft function, no evidence of rejection, minimum 1 to 2 years post-transplant and no or well controlled hypertension. For these women pregnancy generally proceeds without significant adverse effects on mother and child. It is of note that the epidemiological data available to date on azathioprine-based regimens are favourable in the setting of a category D agent (i.e. one that can cause fetal harm). Thus, there is still much to learn regarding potential toxicities of immunosuppressive agents. The effect of improved immunosuppressive regimens which use newer or more potent (and potentially more toxic) agents will require further study.

Genetic toxicities of human teratogens

Birth defects cause a myriad of societal problems and place tremendous anguish on the affected individual and his or her family. Current estimates categorize about 3% of all newborn infants as having some form of birth defect or congenital anomaly. As more precise means of detecting subtle anomalies become available this estimate, no doubt, will increase. Even though birth defects have been observed in newborns throughout history, our knowledge about the causes and mechanisms through which these defects are manifested is limited. For example, it has been estimated that around 20% of all birth defects are due to gene mutations, 5-10% to chromosomal abnormalities, and another 5-10% to exposure to a known teratogenic agent or maternal factor [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis. Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500; K. Nelson, L.B. Holmes Malformations due to presumed spontaneous mutations in newborn infants, N. Engl. J. Med. 320 (1989) 19-23.]. Together, these percentages account for only 30-40%, leaving the etiology of more than half of all human birth defects unexplained. It has been speculated that environmental factors account for no more than one-tenth of all congenital anomalies [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis, Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500]. Furthermore, since there is no evidence in humans that the exposure of an individual to any mutagen measurably increases the risk of congenital anomalies in his or her offspring' [J.F. Crow, C. Denniston, Mutation in human populations, Adv. Human Genet. 14 (1985) 59-121; J.M. Friedman, J.E. Polifka, Teratogenic Effects of Drugs: A Resource for Clinicians (TERIS). The John Hopkins University Press, Baltimore, 1994], the mutagenic activity of environmental agents and drugs as a factor in teratogenesis has been given very little attention. Epigenetic activity has also been given only limited consideration as a mechanism for teratogenesis. As new molecular methods are developed for assessing processes associated with teratogenesis, especially those with a genetic or an epigenetic basis, additional environmental factors may be identified. These are especially important because they are potentially preventable. This paper examines the relationships between chemicals identified as human teratogens (agents that cause birth defects) and their mutagenic activity as evaluated in one or more of the established short-term bioassays currently used to measure such damage. Those agents lacking mutagenic activity but with published evidence that they may otherwise alter the expressions or regulate interactions of the genetic material, i.e. exhibit epigenetic activity, have likewise been identified. The information used in making these comparisons comes from the published literature as well as from unpublished data of the U.S. National Toxicology Program (NTP).

Immunosuppressive drug use during pregnancy

Women with rheumatic diseases frequently need treatment throughout pregnancy and lactation. Physicians must confront the dual challenge of monitoring the possible effects of the underlying maternal disease and the medications on both mother and child. It is essential that the maternal disease be well controlled before, during, and after pregnancy to ensure the best possible outcome for the mother and child. Corticosteroids have been used extensively and safely in pregnant patients with systemic lupus erythematosus and rheumatoid arthritis; there have been no reports of congenital malformations in the exposed infants. There is considerable experience using azathioprine during pregnancy if the maternal condition requires use of a cytotoxic drug; there has been no increased risk of congenital malformations in the exposed infants. There is limited information on the safety of other medications, including 6-mercaptopurine, cyclophosphamide, and cyclosporine. Methotrexate is contraindicated during pregnancy, and chlorambucil should be avoided because there are other effective immunosuppressive agents available for use. Corticosteroids (prednisone and methylprednisolone) can be used safely during lactation. All other immunosuppressive medications, azathioprine and 6-mercaptopurine, chlorambucil, cyclophosphamide, cyclosporine, and methotrexate, are contraindicated during lactation.

Long-term follow-up of patients with Crohn's disease treated with azathioprine or 6-mercaptopurine

BACKGROUND

Crohn's ulcerative gastrointestinal disease is presently managed through a variety of medical interventions, including-according to severity of illness-anti-inflammatory, immunosuppressive, and corticosteroid agents; and with remedial surgery to correct anatomical abnormalities caused by disease processes. The immunosuppressant azathioprine (or its metabolite, 6-mercaptopurine) is considered an efficient maintenance therapy for Crohn's, but there is always concern about bone-marrow suppression, liver damage, and other adverse effects. For how long persons with this disease should be given these drugs has not been determined.

METHODS

Patients who were treated with azathioprine or 6-mercaptopurine for more than 6 months, and who were in prolonged clinical remission (> 6 months without steroids) were followed. The time-to-relapse was analysed in those on treatment, in those who stopped treatment for reasons other than a relapse, and in the whole sample, taking into account that they could be treated with the drugs or not, as a function of time. The influence of concomitant variables on time-to-relapse rate was examined using the Cox proportional hazard model.

FINDINGS

In the 157 patients who continued to take the therapy, cumulative probabilities of relapse at 1 and 5 years were 11% and 32% respectively. Female gender, younger age, and a time for achieving remission more than 6 months were associated with a higher risk of relapse. In 42 patients who stopped therapy, probabilities of relapse at 1 and 5 years were 38% and 75%, respectively. Male gender, younger age and duration of remission less than 4 years were associated with a higher risk of relapse. After 4 years of remission on these drugs, the risk of relapse appeared to be similar, whether the therapy was maintained or stopped.

INTERPRETATION

Taking into account the potential risks of long-term immunosuppressive therapy, the usefulness of maintaining azathioprine or 6-mercaptopurine in patients who have been in remission for more than 4 years is questionable.

Pregnancy in renal allograft recipients: problems, prognosis and practicalities

Improvements in reproductive function invariably follow renal transplantation. The possibility of conception in women of childbearing age emphasizes the need for compassionate and comprehensive counselling. Couples who want a child should be encouraged to discuss all the implications. Therapeutic abortion is undertaken in 20% of conceptions and the spontaneous abortion rate is about 14%, the same as for the normal population. Of the conceptions that continue beyond the first trimester, 93% end successfully. In most women, renal function is augmented during pregnancy, but permanent impairment occurs in 15% of pregnancies. In others there may be transient deterioration in late pregnancy (with or without proteinuria). There is a 30% chance of developing hypertension, pre-eclampsia or both. Preterm delivery occurs in 45-60%, and intrauterine growth retardation in at least 20% of pregnancies. Despite its pelvic location, the transplanted kidney rarely produces dystocia and is not injured during vaginal delivery. Caesarean section should be reserved for obstetric reasons only. Neonatal complications include respiratory distress syndrome, leucopenia, thrombocytopenia, adrenocortical insufficiency and infection. No predominant or frequent developmental abnormalities have been described and data on infancy and childhood are encouraging. Future clinical and laboratory research needs to focus on improving prepregnancy assessment criteria, better understanding of the mechanisms of gestational renal dysfunction, proteinuria and the rare, but devastating, accelerated rejection, assessing the side-effects and implications of immunosuppression in pregnancy and learning more about the remote effects of pregnancy on both renal prognosis and the offspring.

Functional effects of glucocorticoid exposure during fetal life

1. Pregnant rats were exposed to hydrocortisone in a dose of 10 mg/kg on days 9-11 or days 13-15 of gestation. The offsprings born to these mothers were observed for their behavioral development and the response to kainic acid during the infantile period. The response to kainic acid was assessed by the frequency of wet-dog shakes behavior and limbic seizures. 2. The growth rate in the infantile offspring of the 13-15dHc-F1 group showed a slight but significant decrease. 3. All the 13-15dHc-F1 rats exhibited the rearing activity in an open-field at 17 days of age, earlier than in the controls. 4. The ambulatory activity in the 9-11dHc-F1 rats showed a significant decrease at 15 and 17 days of age, whereas no change was shown in the 9-11dHc-F1 rats. 5. The frequency of the wet-dog shakes during the 60 minutes observation after the s.c. injection of 9 mg/kg kainic acid was significantly low in both the 9-11dHc-F1 and 13-15dHc-F1 groups as compared with that in the controls when tested at 25 days of age. The decrease in the response to kainic acid was slightly greater in the 9-11dHC-F1 rats. 6. The frequency of seizures with forelimb clonus and rearing during the 60 minutes observation in the 13-15dHc-F1 was less than that in the controls, whereas no significant difference in the frequency of seizures between the 9-11dHc-F1 and paired control groups was noted. 7. The second generation rats raised from the 9-11dHc-F1 rats by brother-sister mating showed a decrease in the frequency in the kainic acid-induced wet-dog shakes as shown in the F1 offspring. No change in the response to kainic acid was shown in the 13-15dHc-F2 rats.

Pregnancy in organ transplant recipients

Pregnancy in women who are renal transplant recipients carries risks of hypertension and worsening of renal function for the mother and risks of prematurity, growth retardation, and infection in the infant. The risks for mother and child are greater if the transplant recipient has moderate renal insufficiency or hypertension prior to conception; even in patients with moderate renal insufficiency, birth of a viable infant is the rule. Pregnancy should not be discouraged in renal transplant recipients, but both mother and fetus should be carefully followed through the pregnancy and neonatal period. The restoration of fertility should be included as a benefit of transplant in discussions with young women deciding between dialysis and transplant for treatment of renal failure.

Gross and cellular analysis of 6-mercaptopurine-induced cleft palate in hamster

The present study analyzes the morphological, histochemical, and ultrastructural aspects of the pathogenesis of 6-mercaptopurine (6MP)-induced cleft palate in hamster fetuses. Gross and light microscopic observations indicated that 6MP stunts the growth of vertical palatal shelves and thus induces cleft palate. Ultrastructural analysis showed that, in contrast to controls, 6MP-induced alterations were first seen in the mesenchymal cells 24 hr after drug administration. The initial alterations were characterized by swelling of the nuclear membrane. During the next 12 hr, lysosomes were seen first in the mesenchymal cells and then in the cells of the medial edge epithelium (MEE) of the developing palatal primordia. The appearance of lysosomes was temporally abnormal and was interpreted as a sublethal response to 6MP treatment. Subsequently, the nuclear alterations and the lysosomes diminished; and 48 hr after 6MP administration, they were absent from the palatal tissues. Ninety hours after 6MP administration, unlike the controls (in which the palatal shelves were already fused), changes were seen at the epithelial-mesenchymal interface in the developing cleft palatal shelves. These changes were characterized by breakdown of the basal lamina and epithelial-mesenchymal contacts. Eventually, at term, the MEE of the vertical shelf stratified. It was suggested that 6MP affected cytodifferentiation in the palatal tissues during the critical phase of early vertical shelf development and thereby induced cleft palate.

Renal transplantation and pregnancy

Renal transplantation is usually accompanied by an improvement in reproductive function. The possibility of conception in women of childbearing age emphasizes the need for counseling, and couples who want a child should be encouraged to discuss all implications, with the advice based on strict guidelines. If a recipient becomes pregnant, she must be monitored as a high-risk patient. Management requires particular attention to BP control, renal function, and all infection, as well as fetal surveillance. Just under 40% of conceptions do not go beyond the first trimester, but of those that do, greater than 90% end successfully. In most patients, renal hemodynamics improve during gestation, but permanent impairment occurs in 15% of pregnancies. Other patients may experience transient deterioration in late pregnancy (with or without proteinuria). Patients have a 30% chance of developing hypertension, preeclampsia, or both. Despite its pelvic location, the transplanted kidney rarely produces dystocia and experiences no apparent mechanical injury during vaginal delivery. Thus, cesarean section should be reserved for obstetric reasons only. Aseptic technique, bacterial prophylaxis even for trivial surgery, and steroid augmentation are necessary. Preterm deliveries occur in 45% to 60%, and intrauterine growth retardation in at least 20%, of gestations. Neonatal complications include respiratory distress syndrome, leukopenia, thrombocytopenia, adrenocortical insufficiency, and infection. No predominant or frequent developmental abnormalities have been described, and data on infancy and childhood are encouraging. Future goals should be to improve prepregnancy assessment criteria, to reassess the rationale and implications of immunosuppression during pregnancy, and to monitor the remote effects of pregnancy on both renal prognosis and the offspring.

Testing for the chemical induction of aneuploidy in the male mouse

Dyad scores of metaphase II spermatocytes in the mouse have been used as an end point to assess the aneuploidy-inducing potential of three different chemicals; p-fluorophyalanine, phenylalanine and 6-mercaptopurine. The sensitivities of three different spermatogenic stages have been tested; pre-leptotene, zygotene and metaphase I. No effect was found at any treated stage for 6-mercaptopurine and phenylalanine. p-Fluorophenylalanine, when compared to control treatments, did, however, induce non-disjunction when applied at metaphase I. It also caused a delay to spermatogenesis when applied at this stage. The potential of mammalian test systems for the routine screening of chemicals as non-disjunction inducers, is discussed.

Importance of the route of administration for genetic differences in benzo[a]pyrene-induced in utero toxicity and teratogenicity

C57BL/6N (Ahb/Ahb) mice have a high-affinity Ah receptor in tissues, whereas AKR/J and DBA/2N (Ahd/Ahd) mice have a poor-affinity Ah receptor. The cytochrome P1-450 induction response (enhanced benzo[a]pyrene metabolism) occurs much more readily in Ahb/Ahb and Ahb/Ahd than in Ahd/Ahd mice, at any given dose of the inducer benzo[a]pyrene. Embryos from the AKR/J X (C57BL/6N)(AKR/J)F1 and the reciprocal backcross were studied during benzo[a]pyrene feeding of the pregnant females. Oral benzo[a]pyrene (120 mg/kg/day) given to pregnant Ahd/Ahd mice between gestational day 2 and 10 produces more intrauterine toxicity and malformations in Ahd/Ahd than Ahb/Ahd embryos. This striking allelic difference is not seen in pregnant Ahb/Ahd mice receiving oral benzo[a]pyrene. Pharmacokinetics studies with [3H]benzo[a]pyrene in the diet and high-performance liquid chromatographic analysis of benzo[a]pyrene metabolism in vitro by the maternal intestine, liver, and ovary and the embryos of control and oral benzo[a]pyrene-treated pregnant females are consistent with "first-pass elimination" kinetics and differences in benzo[a]pyrene metabolism by the embryos and/or placentas versus maternal tissues. In the pregnant Ahd/Ahd mouse receiving oral benzo[a]pyrene, little induction of benzo[a]pyrene metabolism occurs in her intestine and liver; this leads to much larger amounts of benzo[a]pyrene reaching her embryos, and genetic differences in toxicity and teratogenesis are manifest. In the pregnant Ahb/Ahd mouse receiving oral benzo[a]pyrene, benzo[a]pyrene metabolism is greatly enhanced in her intestine and liver; this leads to less benzo[a]pyrene reaching her embryos, much less intrauterine toxicity and malformations, and no genetic differences are manifest. More toxic metabolites (especially benzo[a]pyrene 1,6- and 3,6-quinones) are shown to occur in Ahd/Ahd embryos than in Ahb/Ahd embryos. In additional studies, no prenatal or neonatal "imprinting" effect in C57BL/6N mice by 2,3,7,8-tetrachlorodibenzo-p-dioxin or Aroclor 1254 on benzo[a]pyrene metabolism later in life was detectable. These genetic differences in intrauterine toxicity and teratogenicity induced by oral benzo[a]pyrene are just opposite those induced by intraperitoneal benzo[a]pyrene [Shum et al., '79; Hoshino et al., '81). The data in the present report emphasize the importance of the route of administration when the teratogen induces its own metabolism.