Effects of chronic prenatal ethanol exposure on hippocampal glutamate release in the postnatal guinea pig.

This study was designed to test the hypothesis that chronic prenatal ethanol exposure decreases basal and stimulated L-glutamate release in the hippocampus of young, postnatal guinea pigs. Timed, pregnant guinea pigs were randomly assigned to one of the following three chronic treatment groups: 4 g ethanol/kg maternal body weight/day, isocaloric-sucrose and pair-feeding to the ethanol group, and water. Each oral treatment was given daily throughout gestation. Spontaneous locomotor activity was increased on postnatal day (PD) 10, and brain and hippocampal weights were decreased on PD 12 in the offspring of the ethanol group compared with the isocaloric-sucrose/pair-fed and water groups. On PD 12, the 45 mM K(+)- and 10 microM veratridine-stimulated release of glutamate in transverse hippocampal slices was decreased in the ethanol group compared with the two control groups. This alteration in glutamate release produced by chronic prenatal ethanol exposure may decrease the efficiency of excitatory synaptic transmission in the hippocampus during postnatal life.     

In vitro ethanol exposure decreases potassium-stimulated, but not veratridine-stimulated, glutamate release in the guinea pig hippocampus.

In this study we determined the effect of in vitro ethanol exposure on stimulated glutamate release in transverse hippocampal slices (400-microm thickness) of the young postnatal guinea pig (PD 12) by using two chemical stimuli with different mechanisms of action. Ethanol (50 mM) decreased K+ (45 mM)-, but not veratridine (10 microM)-, stimulated glutamate release. The study findings demonstrate that in vitro ethanol exposure produces differential inhibition of stimulated glutamate release in the hippocampus, dependent on the stimulating agent.     

Effect of chronic maternal ethanol administration on glutamate and N-methyl-d-aspartate binding sites in the hippocampus of the near-term fetal guinea pig

The objective of this study was to determine the effect of chronic maternal administration of ethanol on hippocampal l-glutamate (glutamate) and N-methyl-d-aspartate (NMDA) binding sites in the near-term fetal guinea pig. Starting on gestational day (GD) 2, pregnant guinea pigs received one of the following oral treatments up to and including GD 62 (term, about GD 68): 4 g ethanol · kg maternal body weight⁻¹ · day⁻¹; isocaloric sucrose and pair-feeding; or water. Maternal blood ethanol concentration was determined at 1 h after the daily ethanol dose on GD 59. Fetuses were studied at GD 63 (mature, near-term fetus). Fetal body weight and brain weight were determined. The density (B_max) and affinity (K_d) of the glutamate and NMDA binding sites in the fetal hippocampus were measured using a radioligand membrane binding assay; saturation analysis was conducted on hippocampal synaptic membrane preparation (HSMP). Maternal blood ethanol concentration on GD 59 was 269 ± 111 (SD) mg/dl (59 ± 24 mM). There was no maternal or embryonic fetal lethality in any of the three treatment groups, and ethanol treatment did not affect maternal body weight gain compared with sucrose or water treatment. Fetal brain weight, but not body weight, was decreased in the ethanol treatment group compared with the sucrose and water treatment groups. The B_max values of the glutamate and NMDA binding sites were decreased in the ethanol treatment group compared with the sucrose and water treatment groups; there was no difference in the K_d values of the glutamate and NMDA binding sites among the three treatment groups. The data demonstrate that, in the guinea pig, chronic maternal administration of a binge-type ethanol regimen throughout gestation restricts brain growth and decreases the density of glutamate and NMDA binding sites in the hippocampus, as manifested in the mature fetus.     

The role of adenosine A1 receptor activation in ethanol-induced inhibition of stimulated glutamate release in the hippocampus of the fetal and adult guinea pig

The role of adenosine A₁ receptor activation in ethanol-induced inhibition of stimulated l-glutamate (Glu) release was determined in transverse hippocampal slices of the near-term fetal guinea pig and the adult guinea pig. Exposure of the slices to 48 mM ethanol inhibited K⁺-stimulated Glu efflux. Pretreatment with 8-cyclopentyltheophylline (CPT), a selective adenosine A₁ receptor antagonist, blocked the ethanol-induced inhibition of K⁺-stimulated Glu efflux in the near-term fetal and adult hippocampus. In the near-term fetus, 2-chloro-N⁶-cyclopentyladenosine (CCPA), a selective adenosine A₁ agonist, and exogenous adenosine each blocked K⁺-stimulated Glu efflux similar to that produced by 48 mM ethanol. In the adult, although K⁺ increased Glu efflux in the presence of CCPA or adenosine, the magnitude of increase was less than that of the K⁺-stimulated Glu efflux for the control condition. Exposure to ethanol alone or ethanol plus CPT produced a transient increase in endogenous adenosine efflux in the near-term fetal and adult hippocampus, which was not temporally related to the ethanol-induced inhibition of K⁺-stimulated Glu efflux. Overall, the data indicate that adenosine A₁ receptor activation mediates ethanol-induced inhibition of stimulated Glu release in the hippocampus of the near-term fetal and adult guinea pig.     

Glutamate and N-methyl-d-aspartate binding sites in the guinea pig hippocampus: Ontogeny and effect of acute in vitro ethanol exposure

The objectives of this study were to characterize the ontogeny of the l-glutamate (glutamate) and N-methyl-d-aspartate (NMDA) binding sites in the developing guinea pig hippocampus, and to determine the effect of acute in vitro ethanol exposure on these binding sites. Specific [³H]glutamate binding and NMDA-sensitive [³H]glutamate binding were determined using a guinea pig hippocampal synaptic membrane preparation (HSMP). To characterize the ontogeny of the density (B_max) and affinity (K_d) of the glutamate and NMDA binding sites, saturation analysis was conducted on HSMP of guinea pigs at gestational day (GD) 50 (immature fetus; term, GD 68), GD 62 (mature, near-term fetus), postnatal day (PD) 13 (neonate), and PD > 60 (adult). To examine the effect of ethanol on the glutamate and NMDA binding sites, HSMP of guinea pigs at GD 50, GD 62, PD 13, and PD > 60 was incubated with ethanol (0–100 mM), followed by determination of specific ['H]glutamate binding and NMDA-sensitive [³H]glutamate binding. To determine the effect of 50 mM ethanol on the B_max, and K_d of the glutamate and NMDA binding sites, HSMP of guinea pigs at GD 62 and PD > 60 was incubated with 0 or 50 mM ethanol followed by saturation analysis. The B_max, values of the hippocampal glutamate and NMDA binding sites were greater at GD 62 and PD 13 compared with GD 50 and PD > 60, but there was no change in the K_d of the binding sites throughout development. Ethanol did not alter hippocampal specific [³H]glutamate binding or NMDA-sensitive [³H]glutamate binding at any of the ages studied, and did not alter the hippocampal B_max or K_d of the glutamate or NMDA binding sites at GD 62 and PD > 60.     

Effects of chronic prenatal ethanol exposure on mitochondrial glutathione and 8-iso-prostaglandin F2alpha concentrations in the hippocampus of the perinatal guinea pig

It is hypothesised that oxidative stress is a key mechanism of ethanol neurobehavioural teratogenicity, resulting in altered endogenous antioxidant status and increased membrane lipid peroxidation in the hippocampus of chronic prenatal ethanol exposure (CPEE) offspring. To test this hypothesis, timed pregnant guinea-pigs (term, approximately gestational day (GD) 68) received chronic daily oral administration of (i) 4 g ethanol kg(-1) maternal bodyweight, (ii) isocaloric sucrose with pair feeding, or (iii) water. At GD 65 (term fetus) and postnatal day (PD) 0 (neonate), individual offspring were killed, the brain was excised and the hippocampi were dissected. Glutathione (GSH) concentration was measured in the cytosolic and mitochondrial fractions of hippocampal homogenate. The occurrence of lipid peroxidation was determined by measuring the concentration of 8-iso-prostaglandin F2+/- (8-iso-PGF2+/-). There was CPEE-induced decreased brain weight and hippocampal weight at GD 65 and PD 0, decreased mitochondrial GSH concentration in the hippocampus at PD 0, with no change in mitochondrial GSH concentration at GD 65 or cytosolic GSH concentration at GD 65 or PD 0, and no change in mitochondrial or whole-homogenate 8-iso-PGF2+/- concentration in the hippocampus at GD 65 or PD 0. The data demonstrate that CPEE produces selective mitochondrial dysfunction in the hippocampus of the neonatal guinea-pig, involving GSH depletion.     

Dose-dependent effects of prenatal ethanol exposure in the guinea pig

The guinea pig is an appropriate animal for studying ethanol central nervous system (CNS) teratogenesis due to its extensive prenatal CNS development. In order to establish an ethanol dosage regimen that produces CNS teratogenesis, the objective of this study was to characterize the dose-dependent effects of chronic ethanol administration on pregnancy outcome and locomotor activity of the offspring. Pregnant guinea pigs received one of the following oral treatments, via intubation into the oral cavity, throughout gestation: 3, 4, 5, or 6 g ethanol/kg maternal body weight/day; isocaloric sucrose and pair feeding; or water. The 5 and 6 g ethanol/kg/day regimens produced maternal death, spontaneous abortion, and perinatal death with at least 75% incidence; the 3 and 4 g ethanol/kg/day regimens produced little or no maternal, embryonic/fetal, or perinatal lethality. The 3 and 4 g ethanol/kg/day regimens did not affect other indices of pregnancy outcome compared with the respective isocaloric-sucrose pair-fed control animals and water-treated animals. The 3, 4, and 5 g ethanol/kg/day regimens increased spontaneous locomotor activity in the offspring, and there was a direct relationship between the magnitude of hyperactivity at days 10 and 60 of age and each of the ethanol dosage regimens and the maternal blood ethanol concentration on day 56 of gestation. The data demonstrate that, in the guinea pig, chronic oral administration of ethanol produces: (a) dose-dependent effects on pregnancy outcome, (b) hyperactivity in the offspring that is dose- (and maternal blood ethanol concentration-) and age-related, and (c) persistent hyperactivity into adulthood with minimal toxicity on pregnancy outcome for the 4 g ethanol/kg/day regimen.     

Chronic ethanol exposure alters MK-801 binding sites in the cerebral cortex of the near-term fetal guinea pig.

The mechanism of ethanol central nervous system (CNS) teratogenesis, resulting from chronic maternal ingestion of high-dose ethanol during pregnancy, is not clearly understood. One of the target sites for ethanol-induced damage in the developing brain is the cerebral cortex. It has been proposed that chronic prenatal ethanol exposure alters NMDA receptors in the developing cerebral cortex. To test this hypothesis, timed pregnant guinea pigs were administered one of the following oral treatments throughout gestation: 4 g ethanol/kg maternal body weight/day; isocaloric sucrose/pair-feeding; water; or no treatment (ad lib). Near-term fetuses were studied at gestational day (GD) 63 (term, about GD 68). This ethanol regimen produced a maternal blood ethanol concentration of 66+/-4 mM (304+/-19 mg/dl) at 1 h after the daily dose on GD 58. The chronic ethanol regimen decreased near-term fetal body weight (12-26% decrease), brain weight (23% decrease), and cerebral cortical weight (21% decrease), compared with the isocaloric sucrose/pair-feeding, and combined water/ad lib experimental groups. Saturation analysis of near-term fetal cerebral cortical membranes using a [3H]MK-801 radioligand binding assay demonstrated a decreased affinity and increased number of MK-801 binding sites for the chronic ethanol regimen compared with the control treatments. These data support the suggestion that upregulation of NMDA receptors in the cerebral cortex after chronic prenatal ethanol exposure could lead to NMDA receptor-mediated excitotoxicity in this brain region.     

Chronic prenatal ethanol exposure alters expression of central and peripheral insulin signaling molecules in adult guinea pig offspring

Maternal ethanol consumption during pregnancy can produce a range of teratogenic outcomes in offspring. The mechanism of ethanol teratogenicity is multi-faceted, but may involve alterations in insulin and insulin-like growth factor (IGF) signaling pathways. These pathways are not only important for metabolism, but are also critically involved in neuronal survival and plasticity, and they can be altered by chronic prenatal ethanol exposure (CPEE). The objective of this study was to test the hypothesis that CPEE alters expression of insulin and IGF signaling molecules in the prefrontal cortex and liver of adult guinea pig offspring. Pregnant Dunkin-Hartley-strain guinea pigs received ethanol (4 g/kg maternal body weight/day) or isocaloric-sucrose/pair-feeding (nutritional control) throughout gestation. Fasting blood glucose concentration was measured in male and female offspring at postnatal day 150–200, followed by euthanasia, collection of prefrontal cortex and liver, and RNA extraction. IGF-1, IGF-1 receptor (IGF-1R), IGF-2, IGF-2 receptor (IGF-2R), insulin receptor substrate (IRS)-1, IRS-2, and insulin receptor (INSR) mRNA expression levels were measured in tissues using quantitative real-time PCR. The mean maternal blood ethanol concentration was 281 ± 15 mg/dL at 1 h after the second divided dose of ethanol on GD 57. CPEE resulted in increased liver weight in adult offspring, but produced no difference in fasting blood glucose concentration compared with nutritional control. In the liver, CPEE decreased mRNA expression of IGF-1, IGF-1R, and IGF-2, and increased IRS-2 mRNA expression in male offspring only compared with nutritional control. Female CPEE offspring had decreased INSR hepatic mRNA expression compared with male CPEE offspring. In the prefrontal cortex, IRS-2 mRNA expression was increased in CPEE offspring compared with nutritional control. The data demonstrate that CPEE alters both central and peripheral expression of insulin and IGF signaling molecules at the mRNA level, which may be related to metabolic dysregulation in adult offspring. Furthermore, altered insulin and IGF signaling may be a mechanism of ethanol neurobehavioral teratogenicity.     

Effects of adolescent ethanol exposure on ethanol consumption in adult rats.

Ethanol exposure during early development could predispose an individual to increased ethanol consumption. Given the high prevalence of adolescent ethanol abuse, it is important to assess the potential impact of adolescent ethanol exposure on the development of alcohol drinking. The following study was designed to assess the initiation of ethanol consumption in adult rats after exposure to ethanol vapors during adolescence. Male Sprague-Dawley rats (n = 23) were exposed to ethanol vapor for 12 h per day for 10 consecutive days between postnatal days 30 and 40. Ethanol vapor exposure maintained blood ethanol levels averaging 250 mg/dl. All rats were subsequently trained to self-administer ethanol after a 52-day withdrawal period. When ethanol consumption was assessed in the adult rats (>3 months old) there were no significant differences in initiation or maintenance of ethanol self-administration between ethanol-exposed and control rats. In addition, there were no group differences in the ability of a noise stressor presented before the drinking session to transiently decrease ethanol intake. Overall, these findings indicate that forced exposure to ethanol vapor during adolescence does not seem to be sufficient to alter initiation or maintenance of limited-access ethanol self-administration.     

Prenatal exposure to ethanol decreases physiological plasticity in the hippocampus of the adult rat

Prenatal exposure to ethanol has been associated with birth defects ranging in severity from physical dysmorphias and profound mental retardation to more subtle compromises of cognitive and behavioral function. Recent evidence has shown the hippocampus to be damaged both morphologically and neurochemically after such exposure in experimental animals. The functional implications of these changes have just recently begun to be addressed. We now report that long-term potentiation and potassium-induced excitability are decreased in hippocampal slices from adult animals exposed to ethanol in-utero. These deficits reflect a decrease in the plasticity of the hippocampal formation. This alteration may be one factor contributing to the memory and learning deficits associated with in-utero exposure to ethanol.     

Effects of adolescent ethanol exposure on sleep in adult rats

Although adolescent ethanol (EtOH) exposure has been associated with long-lasting changes in brain function, little is known as to whether EtOH exposure during adolescence alters sleep and cortical arousal. This study examined protracted alterations in sleep in adult rats exposed to EtOH during adolescence. Adolescent male Wistar rats were exposed to EtOH vapor for 12 h/day for 5 weeks. Cortical electroencephalograms were obtained during 4-h recording sessions after 5 weeks of withdrawal from EtOH. Adolescent EtOH exposure significantly reduced the mean duration of slow-wave sleep (SWS) episodes and the total amount of time spent in SWS in EtOH-exposed rats, compared to controls. Spectral analysis revealed that adolescent EtOH exposure significantly increased cortical peak frequencies during SWS in the 2-4, 4-6, and 6-8 Hz bands. Taken together, our findings suggest that chronic EtOH exposure in adolescent rats reduces measures of SWS, an effect also seen as part of normal aging. Although the cellular and molecular mechanisms mediating the consequences of EtOH exposure on the aging process are not known, the similarities between adolescent EtOH exposure and aging merits further investigation.     

Nitric oxide synthase activity in the hippocampus,frontal cerebral cortex,and cerebellum of the guinea pig: Ontogeny and in vitro ethanol exposure

Decreased nitric oxide (NO) formation, resulting from inhibition of NO synthase (NOS), may be important in the pathogenesis of ethanol central nervous system teratogenesis. The objectives of this study were to determine the ontogeny of NOS activity in the hippocampus, frontal cerebral cortex, and cerebellum of the developing guinea pig, and to test the hypothesis that direct exposure to ethanol inhibits NOS activity in these brain regions at selected developmental ages. NOS activity was quantitated by an optimized radiometric assay. The ontogeny study demonstrated that NOS activity in the hippocampus and frontal cortex was not fully developed prenatally, and apparently increased during postnatal life to attain adult level of activity at postnatal day > 60. In the cerebellum, NOS activity increased during prenatal life to an apparent maximum in the mature near-term fetus at gestational day 63 (term, about 68 days), and then apparently declined during postnatal life to attain adult level of activity. In vitro ethanol exposure (25–100 mM) did not affect NOS activity in the hippocampus, frontal cortex, or cerebellum at any developmental age studied. These data indicate that, although the ontogeny of NOS activity varies between brain regions, ethanol does not directly affect NOS activity in the developing guinea pig. The effects of acute and chronic in utero ethanol exposure on NOS activity in these brain regions are currently being investigated.     

Prenatal exposure to ethanol decreases the sensitivity of the adult rat hippocampus to N-methyl-D-aspartate

Morphological, neurochemical, and electrophysiological studies suggest that the hippocampal formation is one of the brain regions most sensitive to the teratological consequences of prenatal exposure to ethanol. We now report that prenatal ethanol exposure results in a reduction in the sensitivity of the hippocampi of adult offspring to N-methyl-D-aspartate (NMDA). Moreover, it appears that reduced sensitivity to NMDA results from abnormal magnesium regulation of the NMDA receptor-channel complex. These deficits in hippocampal function may underlie some of the behavioral and learning deficits which are characteristic of the offspring of mothers that consume even moderate amounts of ethanol during pregnancy.     

Chronic ethanol exposure increases the non-dominant glucocorticoid,corticosterone, in the near-term pregnant guinea pig

Maternal-fetal signaling is critical for optimal fetal development and postnatal outcomes. Chronic ethanol exposure alters programming of the fetal hypothalamic-pituitary-adrenal (HPA) axis, resulting in a myriad of neurochemical and behavioral alterations in postnatal life. Based on a recent study which showed that human intra-partum fetal stress increased fetal secretion of corticosterone, the non-dominant glucocorticoid, this investigation tested the hypothesis that an established model of HPA axis programming, chronic maternal ethanol administration to the pregnant guinea pig, would result in preferential elevation of corticosterone, which is also the non-dominant glucocorticoid. Starting on gestational day (GD) 2, guinea pigs received oral administration of ethanol (4 g/kg maternal body weight/day) or isocaloric-sucrose/pair-feeding. Each treatment was administered daily and continued until GD 45, 55, or 65 (approximately 3 days pre-term), when pregnant animals were euthanized and fetuses delivered by Caesarean section. Maternal and fetal plasma samples were collected. After sample preparation (protein precipitation and C-18 solid phase extraction), plasma cortisol and corticosterone concentrations were determined simultaneously by liquid chromatography coupled to tandem mass spectrometry. As predicted, chronic ethanol exposure increased both fetal and maternal plasma corticosterone concentration in late gestation. In contrast, plasma cortisol did not differ across maternal treatments in maternal or fetal samples. The plasma concentration of both maternal glucocorticoids increased with gestational age. Thus, corticosterone, the non-dominant glucocorticoid, but not cortisol, was elevated by chronic ethanol exposure, which may have effects on HPA function in later life.     

The influence of acute ethanol exposure on growth hormone release in female rats.

This study investigates the site (hypothalamic or pituitary) at which ethanol (ETOH) alters GH release in female rats. Both the hypothalamic response to clonidine (CLON), an alpha 2-adrenergic agonist, and the pituitary response to growth-hormone releasing hormone (GRH) were tested. Jugular cannulae were inserted for drug administration and undisturbed blood sampling. ETOH was injected IP 24 and 1 h before experimentation. In animals receiving saline or ETOH (1, 2, or 3 g/kg), there was no response to CLON and no difference in GH levels between groups. On the other hand, there was a significant surge in GH release in response to a high dose of GRH (1000 ng/kg) in both saline controls and in ETOH (3 g/kg) animals. Although there was no difference in the height of the surge between groups, baseline GH levels were higher in animals that received ETOH. In response to a low dose of GRH (250 ng/kg) the GH surge was only significant in the ETOH animals. In animals receiving somatostatin antiserum (anti-SRIF; 0.5 ml) in combination with the low GRH dose, the surge in GH levels was significant in both saline and ETOH animals, however, the surge was higher in saline compared to ETOH animals. The results of this study suggest that: 1) ETOH alters the SRIF system (release of reception) in female rats and that this interaction is evident when GRH concentration is low, and 2) ETOH may also inhibit GH release by interfering with the GRH system, however, the site of this influence most likely does not involve an alpha 2-GRH component.     

The effect of acute ethanol exposure on clonidine-induced growth hormone release in male rats

The influence of acute ethanol (ETOH) on the regulation of GH release has not been clearly elucidated. In this study the effect of ETOH on clonidine (CLON)-induced GH secretion was examined. To test the effect of ETOH on CLON-induced GH release doses of 1, 2, and 3 g/kg ETOH in a 25% ETOH/saline solution or 10 ml/kg saline were injected IP 24 and 1 h before CLON (30 micrograms/kg BW IV). Blood samples were withdrawn through a chronic jugular cannula. ETOH was found to alter the GH surge, which occurred 15 min after CLON administration in controls, in a dose-dependent manner. The 1 g/kg dose reduced the GH surge slightly but not significantly. The 2 g/kg dose suppressed the GH surge which was significantly lower than in controls. The 3 g/kg dose eliminated the GH surge completely. To determine if pituitary GH release is directly influenced by ETOH, animals were injected with GRH (250 ng/kg IV) one hour after the second dose of ETOH (3 g/kg IP). There was no difference in the GH surge in control or ETOH-injected animals. Anti-SRIF administered 30 minutes before ETOH or saline did not alter the response to GRH. These results suggest that ETOH reduces the GH responsiveness to alpha 2-GRH stimulation.     

Effects of maternal administration of vitamins C and E on ethanol neurobehavioral teratogenicity in the guinea pig.

Consumption of ethanol during human pregnancy can produce a wide spectrum of teratogenic effects, including neurobehavioral dysfunction. This study, in the guinea pig, tested the hypothesis that chronic maternal administration of antioxidant vitamins C plus E, together with ethanol, mitigates ethanol neurobehavioral teratogenicity. Pregnant guinea pigs received one of the following four chronic oral regimens: ethanol and vitamins C plus E; ethanol and vitamin vehicle; isocaloric-sucrose/pair-feeding and vitamins C plus E; or isocaloric-sucrose/pair-feeding and vehicle. Vitamins C (250 mg) plus E (100mg) or vehicle were given daily, and ethanol (4 g/kg maternal body weight/day) (E) or isocaloric-sucrose/pair-feeding was given for 5 consecutive days followed by 2 days of no treatment each week throughout gestation. One neonate from selected litters was studied on postnatal day (PD) 0. Neurobehavioral function was determined by measuring task acquisition and task retention using an 8-day moving-platform version of the Morris water-maze task, starting on PD 45. Thereafter, in vivo electrophysiologic assessment of changes in hippocampal synaptic plasticity was conducted. There was an ethanol-induced decrease in neonatal brain weight compared with sucrose. The vitamins C plus E regimen protected hippocampal weight relative to brain weight in ethanol offspring, and mitigated the ethanol-induced deficit in the task-retention component of the water-maze task. However, in the sucrose group, this Vit regimen produced deficits in both task acquisition and task retention. The vitamins C plus E regimen did not mitigate the ethanol-induced impairment of hippocampal long-term potentiation. These results indicate that maternal administration of this high-dose vitamins C plus E regimen throughout gestation has limited efficacy and potential adverse effects as a therapeutic intervention for E neurobehavioral teratogenicity.     

Acute inhalation exposure of azodicarbonamide in the guinea pig

Humans have been exposed to azodicarbonamide (ADA) by inhalation where bulk quantities of ADA are handled in the workplace. Responses of some workers have led to concern for the potential irritant and sensitizing properties of inhaled ADA. This study examined the effects of inhaling ADA on lung structure and function of guinea pigs during and after an acute exposure. Groups of 20 guinea pigs were exposed to each of 3 concentrations of ADA (19, 58, and 97 mg/m3), plus air as a control, for 1 hr. Pulmonary function was measured before exposure (baseline), during exposure, immediately after exposure and 24 hr after exposure. Dynamic compliance (Cdyn), total pulmonary resistance (RL), tidal volume (VT), respiratory frequency and minute volume were measured. In addition, gross necropsies and histological examinations of respiratory tract tissues were done either immediately following the exposure or 24 hr after exposure. There were no effects of ADA exposure on gross necropsy, histology, Cdyn, or RL. Some significant, concentration-related decreases in VT, respiratory frequency and minute volume were seen. The magnitudes of these changes were small: the largest change was seen in minute volume, amounting to a 24% decrease in the high concentration group. Inhalation exposure of guinea pigs to ADA at concentrations of up to 97 mg/m3 resulted in minor changes in pulmonary function without any changes in lung histology.