Exaggerated acetaldehyde response after ethanol administration during pregnancy and lactation in rats

Ethanol exposure during late gestation and nursing in the rat: effects upon maternal care, ethanol metabolism and infantile milk intake

Ethanol experiences, during late gestation as well as during nursing, modify the behavioral dynamics of the dam/pup dyad, and leads to heightened ethanol intake in the offspring. This study focuses on: a) behavioral and metabolic changes in intoxicated dams with previous exposure to ethanol during pregnancy and b) infantile consumption of milk when the dam is either under the effects of ethanol or sober. Pregnant rats received water, 1.0 or 2.0 g/kg ethanol, and were administered with water or ethanol during the postpartum period. Intoxication during nursing disrupted the capability of the dam to retrieve the pups and to adopt a crouching posture. These disruptions were attenuated when dams had exposure to ethanol during pregnancy. Ethanol experiences during gestation did not affect pharmacokinetic processes during nursing, whereas progressive postpartum ethanol experience resulted in metabolic tolerance. Pups suckling from intoxicated dams, with previous ethanol experiences, ingested more milk than did infants suckling from ethanol-intoxicated dams without such experience. Ethanol gestational experience results in subsequent resistance to the drug's disruptions in maternal care. Consequently, better maternal care by an intoxicated dam with ethanol experience during gestation facilitates access of pups to milk which could be contaminated with ethanol.

Lactational state modifies alcohol pharmacokinetics in women

BACKGROUND

Given the physiological adaptations of the digestive system during lactation, the present study tested the hypothesis that lactation alters alcohol pharmacokinetics.

METHODS

Lactating women who were exclusively breastfeeding a 2- to 5-month-old infant and 2 control groups of nonlactating women were studied. The first control group consisted of women who were exclusively formula-feeding similarly aged infants, whereas the other consisted of women who had never given birth. A within-subjects design study was conducted such that women drank a 0.4 g/kg dose of alcohol following a 12-hour overnight fast during one test session (fasted condition) or 60 minutes after consuming a standard breakfast during the other (fed condition). Blood alcohol concentration (BAC) levels and mood states were obtained at fixed intervals before and after alcohol consumption.

RESULTS

Under both conditions, the resultant BAC levels at each time point were significantly lower and the area under the blood alcohol time curve were significantly smaller in lactating women when compared with the 2 groups of nonlactating women. That such changes were due to lactation per se and not due to recent parturient events was suggested by the finding that alcohol pharmacokinetics of nonlactating mothers, who were tested at a similar time postpartum, were no different from women who had never given birth. Despite lower BAC levels in lactating mothers, there were no significant differences among the 3 groups of women in the stimulant effects of alcohol. However, lactating women did differ in the sedative effects of alcohol when compared with nulliparous but not formula-feeding mothers. That is, both groups of parous women felt sedated for shorter periods of time when compared with nulliparous women.

CONCLUSIONS

The systemic availability of alcohol was diminished during lactation. However, the reduced availability of alcohol in lactating women did not result in corresponding changes in the subjective effects of alcohol.

Effects of prenatal ethanol exposure and sex on the arginine vasopressin response to hemorrhage in the rat

AVP synthesis, storage, and osmotically stimulated release are reduced in young adult rats exposed prenatally to ethanol (PE). Whether the reduced release of AVP to the osmotic stimulus is due to impairment of the vasopressin system or specifically to an osmoreceptor-mediated release is not known. The present experiments were done, therefore, to determine whether a hemorrhage-induced AVP response would also be diminished in PE-exposed rats. Pregnant rats were fed either a control liquid diet [no prenatal ethanol (NPE)] or a liquid diet with 35% of the calories from ethanol from days 7-21 of pregnancy. Offspring were weaned at 3 wk of life. At 11 wk of age, femoral arterial catheters were surgically placed, and blood volumes were determined at 12 wk. Three days later, two hemorrhages of 10% of the blood volume were performed with samples taken before and 10 min after the hemorrhages. After a 20% blood loss, plasma AVP was 19% higher in NPE rats than in the PE rats despite no differences in mean arterial blood pressure (MABP). Also, hypothalamic AVP mRNA and pituitary AVP content were reduced in PE rats. Furthermore, confirming an earlier report of sex differences in AVP release, the hemorrhage-induced hormone response was twofold greater in female rats than male rats, regardless of previous ethanol exposure. These studies demonstrate that the AVP response to hemorrhage is reduced in PE rats independently of differences in MABP. The data are compatible with a theory of a reduced number of hemorrhage-responsive vasopressinergic neurons capable of stimulated AVP release in PE rats.

The effects of pregnancy on ethanol clearance

We have studied the effects of pregnancy on ethanol clearance rates and on blood and urine ethanol concentrations (BECs and UECs) in adult Sprague-Dawley rats infused with ethanol intragastrically. Pregnant rats had greater ethanol clearance following an intragastric or intravenous ethanol bolus (3 or 0.75 g/kg, respectively) relative to non-pregnant rats (p<0.05). Pregnant rats infused with ethanol-containing diets for several days had lower (p<0.05) UECs than non-pregnant rats when given the same dose of ethanol. Non-pregnant rats infused ethanol-containing diets at two levels of calories (the higher caloric intake required by pregnant rats [220 kca/kg75/d] or the normal calories required for non-pregnant rats [187 kcal/kg75/d]) had statistically equal UECs, suggesting that increased caloric intake was not responsible for the effect of pregnancy. While the activity of hepatic alcohol dehydrogenase (ADH) did not differ with pregnancy, gastric ADH activity was increased (p<0.001). Furthermore, total hepatic aldehyde dehydrogenase (ALDH) and hepatic mitrochrondrial protein were increased (p<0.05) and hepatic CYP2E1 activity was suppressed (p<0.05). The results suggest that pregnancy increases ethanol elimination in pregnant rats by: 1) induction of gastric ADH; 2) elevated hepatic ALDH activity; and 3) increased mitochondrial respiration. The greater ethanol clearance results in lower tissue ethanol concentrations achieved during pregnancy for a given dose, and this may have clinical significance as a mechanism to protect the growing fetus from ethanol toxicity.

Changes in the enterocyte cytoskeleton in newborn rats exposed to ethanol in utero

BACKGROUND

Cytoskeletal changes after longterm exposure to ethanol have been described in a number of cell types in adult rat and humans. These changes can play a key part in the impairment of nutrient assimilation and postnatal growth retardation after prenatal damage of the intestinal epithelium produced by ethanol intake.

AIMS

To determine, in the newborn rat, which cytoskeletal proteins are affected by longterm ethanol exposure in utero and to what extent.

ANIMALS

The offspring of two experimental groups of female Wistar rats: ethanol treated group receiving up to 25% (w/v) of ethanol in the drinking fluid and control group receiving water as drinking fluid.

METHODS

Single and double electron microscopy immunolocalisation and label density estimation of cytoskeletal proteins on sections of proximal small intestine incubated with monoclonal antibodies against actin, alpha-tubulin, cytokeratin (polypeptides 1, 5, 6, 7, 8, 10, 11, and 18), and with a polyclonal antibody anti-beta 1,4-galactosyl transferase as trans golgi (TG) or trans golgi network (TGN) marker, or both. SDS-PAGE technique was also performed on cytoskeletal enriched fractions from small intestine. Western blotting analysis was carried out by incubation with the same antibodies used for immunolocalisation.

RESULTS

Intestinal epithelium of newborn rats from the ethanol treated group showed an overexpression of cytoskeletal polypeptides ranging from 39 to 54 kDa, affecting actin and some cytokeratins, but not tubulin. Furthermore, a cytokeratin related polypeptide of 28-29 kDa was identified together with an increase in free ubiquitin in the same group. It was noteworthy that actin and cytokeratin were abnormally located in the TG or the TGN, or both.

CONCLUSIONS

Longterm exposure to ethanol in utero causes severe dysfunction in the cytoskeleton of the developing intestinal epithelium. Actin and cytokeratins, which are involved in cytoskeleton anchoring to plasma membrane and cell adhesion, are particularly affected, showing overexpression, impaired proteolysis, and mislocalisation.

Effects of acetaldehyde on membrane potentials of sinus node pacemaker fibers

The experiments reported here were performed to characterize the effects of acetaldehyde on membrane potentials (MP) of sinus node subsidiary pacemaker fibers in the absence and presence of adrenergic and cholinergic blockade. Guinea pig sinoatrial preparations were superfused with Tyrode's solution at 37 degrees C while electrically stimulated at 5 Hz. Intracellular microelectrodes were used to record the MP of sinus node subsidiary pacemaker fibers. Acetaldehyde 3 x 10(-6) M and 3 x 10(-3) M had no effect on maximum diastolic potential (MDP), while 3 x 10(-5) M and 3 x 10(-2) M exerted a depolarizing effect on the MDP, without affecting the overshoot (OS). The fall in MDP was associated with a reduction in the amplitude of the action potential (AAP) and the maximum velocity of phase 0 (Vmax 0). The depressant effect of acetaldehyde on MDP was not abolished by adrenergic blockers or atropine. Concentrations of acetaldehyde between 3 x 10(-5) and 3 x 10(-2) M prolonged the action potential duration (APD). Acetaldehyde 3 x 10(-3) M did not affect MDP even in the presence of atropine or propranolol. The APD-prolonging effect of acetaldehyde was not abolished by adrenergic blockers. In summary, the actions of acetaldehyde on MDP and APD were independent of adrenergic and cholinergic mechanisms.

Experimental methods of ethanol administration

Techniques are reviewed for the experimental feeding of alcohol, including a liquid diet procedure invented 25 years ago. This technique results in much higher ethanol intake than with other approaches. As a consequence, various complications observed in alcoholics can be reproduced in animal models. These include fatty liver, hyperlipemia, various metabolic and endocrine disorders, tolerance to ethanol and other drugs, physical dependence and withdrawal and, in the baboon, liver fibrosis and cirrhosis. Variations of the liquid diet formulation are compared, and adequacy of nutrition in terms of minerals, vitamins, lipotropes, carbohydrates and proteins is discussed. The importance of selecting proper controls is emphasized. The respective advantages of three standardized basic rat formulas are reviewed: (i) an all-purpose (35% fat) diet, comparable to the diet previously referred to as the "Lieber-DeCarli formula" and suitable for most experimental applications, particularly those intended to mimic the clinical situation in which the various effects of alcohol occur in the setting of hepatic changes characterized by a fatty liver; (ii) a low-fat diet comparable in all respects to the preceding diet but with a lower fat content, intended to minimize the hepatic changes, and (iii) a high-protein formula particularly useful in those circumstances in which an oversupply of dietary protein might be recommended (i.e. pregnancy). Variations of this technique, including continuous intragastric infusion, are also discussed. It is concluded that, for most experimental studies of chronic alcohol consumption, the liquid diet technique provides one of the most efficient tools to study the effects of ethanol under controlled nutritional conditions because it allows for alcohol consumption of clinical relevance and offers flexibility to adjust to special experimental or physiologic needs by allowing for various substitutions required for a particular experimental design, including changes in lipids, proteins or other dietary constituents. The technique also facilitates the comparison with controls by simplifying the pair feeding and is the best procedure available for the study of the toxic effects of alcohol and their interactions with deficiency or excess of various nutrients.

Effects of acetaldehyde on the automaticity of the guinea pig sinus node

The objective of this investigation was to characterize the effects of acetaldehyde (ACA) on sinus node automaticity (SNA). Guinea pig sinoatrial preparations superfused with Tyrode's solution at 37 degrees C were used. Intracellular microelectrodes were used to monitor SN rate (SNR). Acetaldehyde 3 X 10(-5) M had no effect on SNR, while 3 X 10(-3) M had a positive chronotropic action. The increase in SNR was associated with an increase in the slope of the slow diastolic depolarization (SDD) of subsidiary pacemaker fibers, with no change in the maximum diastolic potential (MDP). Acetaldehyde 3 X 10(-2) M exerted a biphasic effect: the SNR was enhanced and then depressed. Propranolol blocked the positive component of this chronotropic action. The negative component was not modified by propranolol, phentolamine, or atropine. It is concluded that ACA exerts both positive and negative chronotropic actions on the guinea pig sinus node. The positive component of this biphasic effect is mediated through a beta-adrenergic mechanism and it is associated with an increase in the SDD. The negative component is not due to alpha- or beta-adrenergic or muscarinic stimulation.

Comparative metabolic effects of chronic ethanol intake and undernutrition in pregnant rats and their fetuses

Female rats receiving ethanol in the drinking water before and during gestation (ET) were compared to pair-fed animals (PF) and normal controls (C) fed ad libitum. On the 21st day of gestation the maternal body and liver weight, blood glucose, and plasma protein concentrations were lower in ET and PF animals as compared to C. In contrast to C or PF mothers, ET-fed mothers had higher circulating beta-hydroxybutyrate and triacyglyceride levels and beta-hydroxy-butyrate/acetoacetate ratio. Liver triacylglycerides were increased whereas liver glycogen concentration was reduced in ET-fed animals. Only fetal body and liver weights and blood glucose were lower in both ET and PF than in C. Blood beta-hydroxybutyrate was increased and liver glycogen was decreased only in ET fetuses. There were no differences among the groups in fetal circulating beta-hydroxy-butyrate/acetoacetate ratio, plasma proteins, and triacylglycerides or liver triacyglyceride content. Results indicate that certain changes in ET mothers are specifically produced by the ethanol intake rather than undernutrition. Further, metabolic changes occurring in the fetus are influenced by the ethanol effects in the mother and these actions may be added to those directly produced by the ethanol crossing the placenta. However, the collaterals were three times more likely to report more drinking days than the patients; 40.4% (86/213) of the cohabiting contacts reported more drinking days compared to 12.7% (27/213) of the patients reporting more drinking days (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acetaldehyde on polymerization of microtubule proteins

The in vitro effects of ethanol and acetaldehyde on polymerization of calf brain microtubular proteins (MTP) were examined. While ethanol up to 100 mM had no effect on the polymerization of MTP, acetaldehyde above 0.5 mM had an inhibitory effect. This effect was not dependent on the presence of microtubule-associated proteins (MAPs), since acetaldehyde had a similar effect on the polymerization of highly purified tubulin. Electron microscopy revealed that the number and the length of microtubules at equilibrium was reduced by the presence of acetaldehyde. Acetaldehyde raised the critical concentration for tubulin assembly and caused greater inhibition at lower tubulin concentrations. Acetaldehyde augmented the depolymerizing effects of Ca2+ on preassembled microtubules. In addition, acetaldehyde itself caused depolymerization of microtubules but only in the absence of MAPs. Long-term (19.5 h) incubation of MTP with acetaldehyde led to significant loss of polymerization ability which could not be reversed by removal of acetaldehyde. This loss of activity was apparently independent of the observed formation of reducible adducts between acetaldehyde and MTP.

Alcohol and acetaldehyde in rat's milk following ethanol administration

Alcohol and acetaldehyde were measured in milk and peripheral blood in chronic alcoholic rats, at 5 and 15 days of lactation. Ethanol in blood increased throughout lactation and the levels of acetaldehyde were much higher than in nonlactating alcoholic rats. The concentration of acetaldehyde in milk was always ca. 50% of that in blood, whereas that of ethanol varied within the range of 44-80% of the blood levels. Blood alcohol levels in the corresponding sucking pups were much lower than in maternal blood and increased throughout lactation. The time course of ethanol and acetaldehyde concentration in blood and milk were determined in normal lactating rats after cyanamide (40 mg/kg) and ethanol administration (2 or 4 g/kg). Milk alcohol reached higher concentrations than in blood within the first hour of ethanol administration, decreasing and remaining constant thereafter at ca. 65% of those in blood. Acetaldehyde levels in milk were always 35-45% lower than in blood. No alcohol dehydrogenase activity was found in homogenates of mammary tissue; however there was some aldehyde dehydrogenase activity. A significant decrease in mammary tissue aldehyde dehydrogenase was found in chronic alcoholic rats. The role of this enzyme is discussed.

Chronic ethanol intake in lactating rats: milk analysis

Milk was analyzed at 5 and 15 days of lactation in rats fed an ethanol liquid diet or appropriate control diet. Alcoholic rats showed blood ethanol levels as high as 43 mM at the end of lactation. Milk from ethanol-fed rats showed an increase in pH, protein and lipids and a decrease in lactose, compared with controls. Chronic ethanol consumption seems to reduce the yield of milk. The nutritional status of sucklings from alcoholic mothers seems to be related more to the quantity of milk than to its quality.

Blood acetaldehyde response to ethanol ingestion during the reproductive cycle of the female rat

Acetaldehyde could mediate a number of the toxic effects of alcohol both in females and their offspring. Thus, we assessed the blood acetaldehyde response to ethanol (3 g/kg) at various stages of the female reproductive cycle. Blood levels were low throughout the various phases of the estrous cycle and during most of pregnancy. By contrast, a 4-fold rise in maternal blood acetaldehyde occurred at the end of pregnancy (day 20), continued to increase during lactation (17-fold at day 14) and returned to non-pregnant values after weaning or after pup removal at birth. Both enhanced rate of ethanol oxidation and decreased activity of the low Km aldehyde dehydrogenase in liver mitochondria contributed to the increased acetaldehyde levels. Acetaldehyde was detectable in fetal blood, but only a small fraction of the high maternal values in pregnancy reached the fetus through the umbilical vein. Chronic alcohol administration resulted in decreased fetal size and striking enlargement of the placenta with possible implications for abnormal fetal development. Thus, the high maternal acetaldehyde levels at the end of pregnancy may exert deleterious effects on many maternal organs, including those (such as placenta) which are required for normal fetal development.