Effect of D- and/or L-aspartic acids on feeding, drinking, urine outflow and core temperature

Orally Administered D-Aspartate Depresses Rectal Temperature and Alters Plasma Triacylglycerol and Glucose Concentrations in Broiler Chicks

L-Aspartate (L-Asp), D-aspartate (D-Asp) or their chemical conjugates plays important physiological roles in regulating food intake, plasma metabolites and thermoregulation in animals. However, there are very few studies available in layers and no reports have been found in broilers. Broilers are very important commercial birds for meat production, so effects of L- or D-Asp in broilers would provide new physiological insight of this strain. Therefore, the purpose of this study was to determine the effect of oral administration of L- or D-Asp on feed intake, rectal temperature and some plasma metabolites in broiler chicks. Broiler chicks (5 days old) were orally administered with different doses (0, 3.75, 7.5 and 15 mmol/kg body weight) of L- or D-Asp. At 120 min after administration of L- or D-Asp, the blood was immediately collected through the jugular vein. The rectal temperature of chicks was measured at 30, 60 and 120 min after administration using a digital thermometer with an accuracy of ±0.1°C, by inserting the thermistor probe in the rectum to a depth of 2 cm. A repeated-measures two-way ANOVA was applied for the analysis of feed intake and rectal temperature. Plasma metabolites were statistically analyzed by one-way ANOVA and regression equations. The study showed that oral administration of both L- and D-Asp did not alter feed intake. However, D-Asp, but not L-Asp, dose-dependently decreased the rectal temperature in chicks. It was also found that D-Asp increased plasma glucose and decreased triacylglycerol concentrations. The changes in plasma metabolites further indicate that D-Asp treatment modulates the energy metabolism in broiler chicks. In conclusion, D-Asp may be a beneficial nutrient not only for layers but also for broilers, since orally administered D-Asp lowered rectal temperature without reducing feed intake.

Oral administration of D-aspartate, but not L-aspartate, depresses rectal temperature and alters plasma metabolites in chicks

AIMS

L-Aspartate (L-Asp) and D-aspartate (D-Asp) are physiologically important amino acids in mammals and birds. However, the functions of these amino acids have not yet been fully understood. In this study, we therefore examined the effects of L-Asp and D-Asp in terms of regulating body temperature, plasma metabolites and catecholamines in chicks.

MAIN METHODS

Chicks were first orally administered with different doses (0, 3.75, 7.5 and 15 mmol/kg body weight) of L- or D-Asp to monitor the effects of these amino acids on rectal temperature during 120 min of the experimental period.

KEY FINDINGS

Oral administration of D-Asp, but not of L-Asp, linearly decreased the rectal temperature in chicks. Importantly, orally administered D-Asp led to a significant reduction in body temperature in chicks even under high ambient temperature (HT) conditions. However, centrally administered D-Asp did not significantly influence the body temperature in chicks. As for plasma metabolites and catecholamines, orally administered D-Asp led to decreased triacylglycerol and uric acid concentrations and increased glucose and chlorine concentrations but did not alter plasma catecholamines.

SIGNIFICANCE

These results suggest that oral administration of D-Asp may play a potent role in reducing body temperature under both normal and HT conditions. The alteration of plasma metabolites further indicates that D-Asp may contribute to the regulation of metabolic activity in chicks.

Evaluation of D-amino acid levels in rat by gas chromatography-selected ion monitoring mass spectrometry: no evidence for subacute toxicity of orally fed D-proline and D-aspartic acid

Sprague-Dawley rats received deionized water (controls) during 28 days or drinking water with added D-proline, L-proline, D-aspartic acid or L-aspartic acid corresponding to a mean daily load of approximately 50 mg amino acid enantiomer kg-1 body weight. Parameters indicating the physiological status (food intake and body weight, glutamic-oxalic-transaminase, glutamic-pyruvic-transaminase, alkaline phosphatase, urea and creatinine in serum, and creatine and osmomolality of urine) were determined. After 28 days the weights of the supposed target organs of toxicity (kidney, liver, brain, thymus) were determined and organs were inspected for macroscopic and microscopic alterations. No pathological changes in the organs were observed and no signs of subacute toxicity (liver, kidney) were found. In serum, homogenates of liver, kidney and brain, and in part, in urine, the amounts of D-amino acids (D-AAs) were quantitatively determined using chiral phase capillary gas chromatography-selected ion monitoring mass spectrometry. Significant levels of certain D-AAs (Ala, Pro, Ser, Asx, Glx, Orn and Lys) were already detectable in kidney and liver homogenates and serum of controls. In brain homogenates the highest amounts among the D-AAs were found for D-Ser (up to 382 nmol g-1), moderate amounts for D-Ala, D-Asx and D-Glx, and, in a few cases, trace amounts for D-Orn and D-Lys (1-2 nmol g-1). D-Pro was not detected either in the brains of controls or in the brains of animals loaded with D-Pro. Feeding with D-Pro resulted in a 20-30 fold increased renal excretion of D-Pro at the end of the experiment. Continuous feeding with D-Asp did not increase renal excretion of this enantiomer, but in the serum, higher amounts (0.8-4.0 mumol-1) were determined in comparison to the control group (0.3-0.9 mumol-1). Feeding with D-Pro led to an increase of this enantiomer in serum (1.3-10.5 mumol-1). Feeding with D-Asp did not increase its amounts in brain homogenates (38 and 43 nmol g-1) in comparison to controls.

Antinociceptive effect of D-aspartic acid in mice

The effects of D- and L-aspartic acids on the nociceptive tail flick reflex in mice were investigated. D-Aspartic acid (115-230 mg/kg, IP) was found to increase tail flick latency significantly. Naloxone (0.1 mg/kg) abolished the analgesic effect of D-aspartic acid (115 mg/kg). Morphine and D-aspartic acid, when combined at their nonanalgesic doses, led to significant analgesia. It may be concluded that the opioid system is involved in the antinociceptive effect of D-aspartic acid. Both morphine and D-aspartic acid were previously reported to inhibit L-aspartic acid production via blockade of L-asparaginase. L-Aspartic acid, which was ineffective alone, significantly inhibited the antinociceptive effects of both D-aspartic acid and morphine.

Suppression by ketamine and dextromethorphan of precipitated abstinence syndrome in rats

The development of physical dependence on opiates appears to involve an inhibition by opiates of L-asparaginase and glutaminase, and the blockade by opiates of aspartatergic (ASPergic)/glutamatergic (GLUergic) receptors. Ketamine (K) (0.5 or 1 mg/kg) or dextromethorphan (DM) (1 or 2 mg/kg), both of which are known to decrease the responsiveness of ASPergic/GLUergic receptors, were administered to the three morphine (M)-containing pellets implanted rats prior to 2 mg/kg naloxone (NL) injection. Whereas 0.5 mg/kg K showed no significant effect on abstinence syndrome signs, 1 mg/kg K and 1 mg/kg DM significantly attenuated some of the signs. The attenuation or prevention of all the signs were observed after 2 mg/kg DM administration. Almost complete prevention was seen from the second minute on during the ten-minute observation period. As ASP and GLU antagonists K and DM have this antagonizing effect on the precipitated abstinence syndrome signs, the manifestation of abstinence syndrome may mainly result from the normalization of ASP and GLU production because of the disinhibition by NL of the enzymes and the stronger stimulation of ASPergic/GLUergic receptors which have no opiate blockade after NL injection.

Intensification and attenuation of morphine dependence by D-aspartic acid and PLG

The inhibition by opiates and the sudden normalization by opioid antagonists of the brain L-asparaginase activity (BAA) have previously been reported to be the main factors in the development of physical dependence and the manifestation of precipitated abstinence syndrome, respectively. As a result, L-asparaginase inhibitors D-aspartic acid and prolyl-leucyl-glycinamide (PLG) were separately given to mice and rats either just after morphine (M)-containing pellet implantation or 15 min before naloxone (NL)-precipitated abstinence syndrome. The animals treated in this manner were used to assess the intensity of the physical dependence and to determine the BAA. D-ASP or PLG administration following pellet implantation significantly increased all of the observed signs such as flying, jumping, wet dog shake and writhing. When D-ASP or PLG were given 15 min before precipitated abstinence they significantly decreased the number of the signs. The determination of the BAA showed significant decreases or increases more or less parallel to the severity of the physical dependence on M. The intensification of physical dependence by D-ASP or PLG given just after the pellet implantation was attributed to their additional inhibitory effect to that of M on the BAA at the beginning of the physical dependence development. The attenuating effect of BAA inhibitors D-ASP or PLG administered before precipitated abstinence was explained with the prevention of the increase in the BAA.

Administration of D-aspartate increases D-aspartate oxidase activity in mouse liver

Oral administration of D-aspartate to mice for 2 weeks by addition of the amino acid to drinking water produced a nearly 4-fold increase in liver D-aspartate oxidase (EC 1.4.3.1) activity, whereas no increase was induced by L-aspartate administered in the same way. Administration of D-aspartate also produced a small significant increase in the kidney enzyme activity, but L-aspartate administration increased the activity as well. The enzyme activity in the brain and muscle was not affected by administration of either D- or L-aspartate. Intraperitoneal administration of D-aspartate increased the enzyme activity only in the liver, and other compounds tested, including D-glutamate and D-alanine, could not replace D-aspartate. The results indicate a specific relationship between D-aspartate and D-aspartate oxidase and suggest that the amino acid is, in fact, a physiological substrate of the enzyme.

Aggravation by morphine and D-aspartic acid of pyelonephritis induced by i.v. inoculation of Staphylococcus aureus in rats

Experimental pyelonephritis was induced by intravenous inoculation of Staphylococcus aureus in homozygous Brattleboro diabetes insipidus (Hom Brattleboro DI), heterozygous Brattleboro (Het Brattleboro) and Wistar rats. One group of rats from each strain was implanted with morphine-containing pellet three days before inoculation. Another series of groups received D-aspartic acid (D-ASP) intraperitoneally, starting three days before inoculation throughout the experiments. Owing to the inhibition by morphine or D-ASP of food intake, another control group from each strain was subjected to food restriction. Pyelonephritis development on the tenth day of inoculation was evaluated by the determination of viable bacteria in urine and total kidney tissue, and pathomorphological lesions in kidney. Hom Brattleboro DI rats appeared more resistant. Morphine or D-ASP significantly increased the findings in three strains of rat.

The inhibition by morphine and D-aspartic acid of antibody production against Salmonella typhimurium antigen in rats: its antagonism by L-aspartic acid

The changes in the production of antibody against Salmonella typhimurium antigen were investigated in rats by means of the agglutination test after chronic oral administration of the L-asparaginase inhibitors morphine (M) or D-aspartic acid (D-Asp) alone or together with L-aspartic acid (L-Asp) and food restriction, all of which had been started five days before the injections of antigen. The statistical evaluation, carried out after the titers had been defined as -log2 of the highest dilution giving a positive agglutination reaction, showed that M or D-Asp significantly decreased antibody production in comparison with the immunized control or food restricted group. The concomitant administration of L-Asp appeared to significantly antagonize the inhibitory effect of both M and D-Asp. Therefore, the results were considered as further supporting evidence for the fact that the deleterious effect of M on the immune system and its functions might be related to the inhibitory effect of M on L-asparaginase activity.

Brain asparaginase, ACE activity and plasma cortisol level in morphine dependent rats: effect of aspartic acid and naloxone

The activities of the brain L-asparaginase and angiotensin converting enzyme (ACE), and the plasma cortisol level were found to be decreased in the rats implanted with morphine (M) containing pellets. Even though 10 mg/kg of naloxone (N) itself showed an inhibitory effect on ACE it abolished the inhibitions seen in the M dependent rats five min following subcutaneous injection. The chronic administration of L-aspartic acid (ASP) during the development of physical dependence or just before the N injection prevented the increase of the plasma cortisol caused by N. It is concluded that in addition to the inhibition of the brain L-asparaginase activity which was previously hypothesized to be the main reason of the development of physical dependence on opiates as a result of the related experimental and clinical data, the inhibition by M of the brain ACE activity may take part in the development of physical dependence. With regard to the plasma cortisol level, the concomitant administration of ASP with M blocks, to a great extent, the development of physical dependence on opiate. The single dose of ASP administration before N injection prevents the effect of N, the manifestation of abstinence syndrome.

The in vitro and in vivo effects of enkephalins and beta-endorphin on ACE activity in mice

The in vitro and in vivo effects of naloxone (NAL) and endogenous opioids namely methionine and leucine enkephalins (MET-ENK, LEU-ENK) and beta-endorphin (BETA-END) on the brain and lung angiotensin converting enzyme (ACE) activities were investigated. All three peptides dose -dependently inhibited ACE activity in vitro except 10(-5) M concentration of BETA-END which increased the lung ACE activity. NAL which intensified the in vitro inhibitory effect of the used opioids showed an antagonistic effect on the in vivo suppressive effect of BETA-END on both brain and lung ACE activities whereas it had neither antagonistic nor synergistic effect on the in vivo inhibiting effect of MET-ENK and LEU-ENK on the lung ACE activity. The results were consistent with those obtained by using morphine and NAL. As a result the possible contributory action of the excessively released endogenous opioids to overcome shock via their inhibiting effect on ACE was discussed.

Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents: II

This survey begins a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published since 1978, but data from many earlier papers are also tabulated.

Changes in brain and lung angiotensin converting enzyme activity in various shocks

The brain and lung angiotensin converting enzyme (ACE) activities of the rats subjected to haemorrhagic, hypovolemic or endotoxic shock and of the mice immunized and then intravenously challenged with bovine serum albumin were determined by means of a spectrophotometric method. The lung ACE activities of all the shock groups were found significantly higher than those of their Control groups whereas only the brain ACE activities of the rats in endotoxic shock and the mice in anaphylactic shock showed a significant increase compared to their own control values. The results were interpreted as supporting evidence for the idea that peripheral and central renin-angiotensin systems may play a deleterious role in shock.

Vasopressin release by D-aspartic acid, morphine and prolyl-leucyl-glycinamide (PLG) in DI Brattleboro rats

The L-asparaginase activities of the brains of the Wistar, heterozygous and homozygous Brattleboro rats divided into three parts namely the anterior, middle and posterior which respectively contained cerebral cortex, hippocampus + midbrain + thalamus + hypothalamus cerebellum + pons + medulla oblongata were estimated. The L-asparaginase activities of all the three parts in the homozygous Brattleboro rats were significantly higher than in the Wistar rats as well as in the heterozygous Brattleboro rats. Twenty min following the injections of 200 mg/kg D-aspartic acid, 20 mg/kg morphine, 200 mg/kg D-aspartic acid + 20 mg/kg morphine, 6 mg/kg prolyl-leucyl-glycinamide (PLG) and 6 mg/kg PLG + 20 mg/kg morphine the L-asparaginase activities of all three parts of the homozygous Brattleboro rat brains were found to be significantly inhibited. After having seen the suppressive effect of the drugs and their combinations used before the homozygous Brattleboro rats were given D-aspartic acid, morphine, D-aspartic acid + morphine, PLG and PLG + morphine for seven days. Then their plasma vasopressin levels were determined by RIA. The treatments applied to the homozygous Brattleboro rats caused the appearance of a significant amount vasopressin in the plasma. The results were interpreted as evidence for the fact that the inhibition of the brain L-asparaginase provides and/or accelerates the biosynthesis and/or release of vasopressin. As morphine has a vasopressin releasing and a brain L-asparaginase inhibiting effect the antidiuretic action of morphine was considered to be linked to its inhibitory effect on the brain L-asparaginase.

Feeding, drinking, urine osmolality in DI Brattleboro rats: changes by morphine, naloxone, D-amino acids, prolyl-leucyl-glycinamide (PLG)

Brattleboro rats placed in metabolism cages were injected with morphine (Mor), naloxone (Nal), D- and L-aspartic acid (D- and L-Asp), D-phenylalanine (D-Phe), D-leucine (D-Leu) and prolyl-leucyl-glycinamide (PLG), alone and in suitable combinations. Food and fluid intake, urine outflow, faeces weight, rectal temperature and urinary osmolality were determined at the end of seven hours period of time. Mor, Nal, D-Asp and PLG alone caused a significant decrease in food and fluid intake, urine volume and faeces weight and a significant increase in urinary osmolality being the osmolality of the Mor, D-Asp and PLG injected groups higher than 300 mOsmol/kg. The combination of Nal with Mor, D-Asp and PLG appeared to intensify the changes induced by Mor, D-Asp and PLG whereas L-Asp antagonized the majority of changes caused by Mor or PLG. The results were discussed in the light of the previous experimental findings.

The effect of morphine, naloxone, D- and L-aspartic acid on the brain and lung ACE in mice

The brain and lung angiotensin converting enzyme (ACE) activities of the mice injected with 10 mg/kg morphine and/or naloxone, 200 mg/kg D- and/or L-aspartic acid were spectrophotometrically determined. Morphine, naloxone, D- and L-aspartic acid alone inhibited both brain and lung ACE activities whereas the combinations of morphine with naloxone, D-aspartic acid with L-aspartic acid and morphine with naloxone + L-aspartic acid showed no inhibitory effect on the brain ACE. While naloxone or L-aspartic acid partly antagonized the suppression of morphine on the lung ACE their combination completely prevented morphine from inhibiting the lung ACE. In the in vivo experiments performed on the brain and lung homogenates of the untreated mice the determination of the ACE activity in the incubating media containing 3.10(-3) M morphine or naloxone, 10(-2) M D- or L-aspartic acid showed a significant decrease in the activity. But no in vitro antagonistic effect was found by using the combinations of the drugs used in the study. The antagonism seen in the in vivo experiments was considered as an indirect one. And the relationship between the inhibitory effect of morphine, naloxone and D-aspartic acid, their suppressive effect on drinking and their beneficial effects in various forms of shock was discussed.