Biomedical subjects

M Stangassinger

Publications and source records attributed to M Stangassinger.

At least 37 records · Page 2Linked to original sources

PubMed1998

Skeletal effects of low-dose cyclosporin A in aged male rats: lack of relationship to serum testosterone levels.

The aim of this study was to investigate the skeletal effects of cyclosporin A (CsA) in a dose range relevant to clinical medicine in lumbar vertebral cancellous bone of aged male rats and to correlate these effects with possible changes in serum testosterone levels. Thirty-one 18-month-old male Wistar rats were divided into four weight-matched groups and subcutaneously injected with either 0, 1, 3, or 5 mg of CsA/kg of body weight three times per week After 4 weeks of treatment, all rats were killed after in vivo fluorochrome labeling and the first lumbar vertebrae analyzed by quantitative histomorphometry. Serum was analyzed for total calcium, creatinine, alkaline phosphatase, osteocalcin, parathyroid hormone, total testosterone, and CsA levels. CsA administration resulted in a dose-dependent increase in serum osteocalcin levels and in histomorphometric indices of cancellous bone turnover in the axial skeleton. Furthermore, CsA-treated rats showed a deterioration of vertebral cancellous bone structure with increased discontinuity of the trabecular bone network due to trabecular plate perforations. Serum testosterone levels were not significantly changed by CsA treatment and were uncorrelated to all biochemical or histomorphometric indices of bone turnover. We conclude that the 4-week administration of CsA at doses that are close to those used in transplantation patients induced high turnover osteopenia in the axial skeleton of aged, 18-month-old male rats, and that these effects were likely not mediated by changes in serum testosterone levels.

Aging↗

PubMed1997

Prophylactic effects of 1,24,25-trihydroxyvitamin D3 on ovariectomy-induced cancellous bone loss in the rat.

Vitamin D metabolites can prevent estrogen depletion-induced bone loss in ovariectomized (OVX) rats. In this study, we investigated the bone-sparing effects of oral 1alpha,24R,25-trihydroxyvitamin D3 (1,24,25(OH)3D3) in a wide dose range in aged OVX rats. Fifty-three female Fischer-344 rats (6 months old, 170 g BW) were either ovariectomized or sham-operated (SHAM). Eight rats served as baseline controls. Groups of OVX rats (n = 7-8 each) received vehicle alone or graded oral doses of 1,24,25(OH)3D3 (0.05, 0.1, 0.2, and 0.3 microg/kg BW/day), starting five days after surgery. Urine and blood samples were collected one, two, three, and four months after surgery. Serum samples were analyzed for total calcium and alkaline phosphatase. Calcium, hydroxyproline, and collagen crosslinks (HPLC) were determined in urine. After fluorochrome double labeling, the rats were sacrificed four months postsurgery and the first lumbar vertebrae and the proximal tibiae were processed undecalcified for bone histomorphometry. Ovariectomy induced a 28% and a 69% reduction in vertebral and tibial cancellous bone area, respectively. Osteopenia in OVX rats was associated with increased histomorphometric and biochemical indices of bone turnover. The administration of 1,24,25(OH)3D3 to OVX rats dose-dependently increased vertebral and tibial cancellous bone mass, serum calcium, and urinary calcium excretion, and reduced histomorphometric and biochemical indices of bone resorption. 1,24,25(OH)3D3 at doses of 0. 2 and 0.3 microg/kg/day produced strong anabolic effects, especially on vertebral cancellous bone in OVX rats, and increased mineral apposition rate and wall width of completed remodeling units relative to vehicle-treated OVX rats. Even at high doses, 1,24, 25(OH)3D3 did not impair bone mineralization. We conclude that oral administration of 1,24,25(OH)3D3 can effectively prevent estrogen depletion-induced cancellous bone osteopenia in the aged OVX rat model. The therapeutic window for 1,24,25(OH)3D3 in OVX rats, however, is also narrow, comparable to that for calcitriol.

Alkaline Phosphatase↗

PubMed1997

1alpha-hydroxyvitamin D2 partially dissociates between preservation of cancellous bone mass and effects on calcium homeostasis in ovariectomized rats.

Vitamin D metabolites can prevent estrogen depletion-induced bone loss in ovariectomized (OVX) rats. Our aim was to compare the bone-protective effects of 1alpha,25-dihydroxyvitamin D3 (1, 25(OH)2D3), 1alpha,25-dihydroxyvitamin D2 (1,25(OH)2D2), 1alpha-hydroxyvitamin D3 (1alpha(OH)D3), and 1alpha-hydroxyvitamin D2 (1alpha(OH)D2) in OVX rats. 1alpha(OH)D3 and 1alpha(OH)D2 are thought to be activated in the liver to form 1,25(OH)2D3 and 1, 25(OH)2D2, respectively. Forty-four 12-week-old female Fischer-344 rats were either OVX or sham-operated (SHAM). Groups of OVX rats (n = 7 each) received vehicle alone, 1,25(OH)2D3, 1,25(OH)2D2, 1alpha(OH)D3, or 1alpha(OH)D2, starting 2 weeks after surgery. All vitamin D metabolites were administered orally at a dose of 15 ng/day/rat. Urine and blood samples were collected 6, 9, 12, and 16 weeks after surgery. Serum samples were analyzed for total calcium and phosphate. Calcium, phosphate, creatinine, and free collagen cross-links (ELISA) were determined in urine. After tetracycline double labeling, the rats were sacrificed 16 weeks postsurgery, and the proximal tibiae and the first lumbar vertebrae were processed undecalcified for static and dynamic bone histomorphometry. 1,25(OH)2D3 and, to a slightly lesser extent, 1,25(OH)2D2 elevated vertebral cancellous bone mass in OVX rats to a level beyond that observed in SHAM animals, and both compounds increased serum calcium and urinary calcium excretion to similar extents. 1alpha(OH)D3 and 1alpha(OH)D2 resulted in a 64% and 84%, respectively, inhibition of ovariectomy-induced vertebral cancellous bone loss. In the proximal tibial metaphysis, all vitamin D metabolites tested could only partially prevent post-OVX trabecular bone loss, with a tendency for 1alpha(OH)D3 to be the least active compound. The effects of 1alpha(OH)D3 and 1alpha(OH)D2 on calcium homeostasis differed markedly, however. The mean increase in urinary calcium excretion over the whole experiment was fivefold for 1alpha(OH)D3, whereas the corresponding increase for 1alpha(OH)D2 was only twofold. We conclude that, compared with 1alpha(OH)D3, 1alpha(OH)D2 combined at least equal or higher bone-protective activity in OVX rats with distinctly less pronounced effects on calcium homeostasis. This effect was not due to a differential action of the corresponding main activation products, 1,25(OH)2D3 and 1,25(OH)2D2.

Animals↗

PubMed1997

Helper activity of chicken V beta 1+ and V beta 2+ alpha beta T cells for in vitro IgA antibody synthesis.

Chickens have only two T cell receptor variable beta gene families: V beta 1 and V beta 2 (1). In our previous work we found that IgA production was almost completely suppressed in chickens depleted of V beta 1+ alpha beta T cells by treatment with a TCR V beta 1-specific monoclonal antibody (2), while IgM and IgG production was not affected. Our present results indicate that, in vitro, both V beta 1+ and V beta 2+ chicken cecal tonsil T cells provide help for the differentiation of cecal tonsil IgA B cells, suggesting that the failure of V beta 1+ T cell-depleted chickens to produce IgA is not caused by the inability of V beta 2+ T cells to provide help for IgA production by B cells, but rather by the scarcity of these T cells in mucosal tissues (3), where most IgA responses are induced (4).

Animals↗

PubMed1997

[Estimation of marker passage in the digestive tract of dairy cows by different models: influence of stage of lactation, amount of intake and diet composition].

12 dairy cows were used to examine the influence of stage of lactation, amount of intake and diet composition on digesta passage from the reticulorumen. Cows were fed on mixed diets, containing on average 34% concentrate and 66% roughage (dry matter basis). The roughage portion consisted of maize silage and either extensively or intensively produced grass silage in the ratio of 40:60 (% as fed). Titanium(IV)-oxide (TiO2) was used as a marker and faecal marker concentrations were determined for 120 h after oral dosing. Samples were taken in four periods-ante partum (1 period) and in the first half of lactation (3 periods)-, each period representing a certain physiological state. Cows were fed according to milk yield with mean dry matter intakes of 12.0, 16.8, 22.6 and 21.2 kg in periods 1 to 4. Passage parameters were estimated by a model with gamma time-dependency (G4G1), by an exponential model and by a model calculating total tract mean retention time as mean value of all points on the marker-excretion curve. Results showed an obvious acceleration of marker passage from the reticulorumen from ante partum to post partum. Total tract mean retention time calculated as mean values of all points on the marker excretion-curves were in good agreement with total tract mean retention times calculated with G4G1. Passage rates from the reticulorumen showed poor agreement between G4G1 and the exponential model. Effects of period and diet past partum were observed for rate of passage from and mean retention time in the fast compartment only, both estimated by G4G1. TiO2 appears to be a suitable marker to estimate passage rates. Values for passage rates were in the range of those reported for concentrate particles by others.

Animals↗

PubMed1997

[Determination of the passage of two markers in the gastrointestinal tract of steers using different evaluation methods: effect of the level of nutrition].

This study was conducted to investigate the effects of amount of intake of a mixed diet by steers on the passage of digesta through the reticulorumen and the whole digestive tract. Six ruminally cannulated steers received a mixed diet consisting on average of 43% grass silage, 25% maize silage, 30% concentrate and 2% mineral-vitamin mix in DM. The experimental design was a repeated 3 x 3 Latin square with 21 days periods. The diet was offered twice daily (07.00 and 19.00 h) at 1, 1.5 and 2 times of estimated maintenance energy requirements. At the beginning of each period, animals received pulse doses of Titanium(IV)-oxide (TiO2) per os and Cr-EDTA intraruminally. Following marker administration, faecal marker concentrations were determined over 120 h. Passage parameters were estimated by a mono-exponential and a bi-exponential model, by models including gamma age-dependency and by a model calculating total tract mean retention time as mean value of all points on the marker-excretion curve. Passage rate of TiO2 from the reticulorumen increased with higher intakes, whereas mean retention time in the whole tract decreased. In general, results of different models were consistent across intakes. Values for passage of TiO2 were in good agreement with those reported for small particles, when similar diets were fed to cattle. Rate of passage of Cr-EDTA from the reticulorumen increased with higher intakes, and mean retention times of Cr-EDTA in the reticulorumen and in the whole tract decreased. Differences between models with or without age dependency were greater for Cr-EDTA than for TiO2. Fit to Cr-EDTA excretion curves was not satisfactory for models with gamma age dependency. Irrespective of model and marker, passage from the reticulorumen accelerated markedly, whereas retention times in the reticulorumen and in the whole tract decreased, as intake increased from maintenance energy requirements to 1.5 times maintenance.

Aging↗

PubMed1997

[Systemic availability of bovine immunoglobulin G and chicken immunoglobulin Y after feeding colostrum and whole egg powder to newborn calves].

In connection with a study on the prophylaxis of infectious diarrhea with specific egg yolk antibodies, the systemic availability of colostral bovine immunoglobulin G (bIgG) and chicken immunoglobulin Y (IgY) after feeding egg powder was investigated on 26 newborn calves from 23 different farms. Blood was sampled daily and at the same day time from these calves in the first 14 days of life. During the feeding of colostrum, the mean bIgG concentration was highest at day 1 post natum with a value of 9.3 mg/ml serum. Thereafter, the mean bIgG level was reduced continuously to a significant lower concentration of 4.9 mg/ml serum at day 12 post natum and remained nearly constant at 5.2 mg/ml till to the end of the observation period. Total protein concentrations in the serum did not change and plateaued at a mean value of 56.2 mg/ml (SD 11.2). The number of colostrum meals had no significant effect on the mean bIgG concentrations during that period. The individual variation of bIgG concentrations was very high on every day of the sampling period. The mean coefficient of variation was at 52.1 % (SD 5.7). After having described the individual bIgG concentration curves mathematically with a regression curve, two groups with significantly different bIgG elimination constants (k) could be obtained. Thus in one group (n = 10) with k-values of < -0.02 a mean half time of serum bIgG of 24.3 days (SD 4.6) was calculated. In the other group of calves (n = 16) with elimination constants of k > -0.02, a mean half time of 68.5 days (SD 36.7) could be calculated, possibly because these calves started earlier with their endogenous bIgG production. Additionally, to 18 of these calves 20 g egg powder with an IgY concentration of 15 mg/g was fed up to day 14. Calves had a maximal mean IgY concentration of 1.9 micrograms/ml serum if egg powder feeding started already during the first 12 hours of life. Starting at a later time resulted in a significant reduction of IgY levels. For example, the mean initial IgY concentration dropped to 0.035 micrograms/ml serum after having had the first egg powder application between 25 and 48 hours post natum. Using the individual IgY elimination constant derived from a regression analysis (r2 = 0.84) of the IgY concentration curve, a mean IgY half time of 5.0 days (SD 2.5) could be calculated. To prevent the absorption of heterologous antibodies and consecutively, also to prevent a possible systemic effect, egg powder for prophylactic purposes in newborn calves should be fed after the first 24, better 48 hour, post natum. Most important for the prophylactic effect of specific antibodies on infectious diarrhea is not their systemic but their high local intestinal availability.

Animals↗

PubMed1996

[Freund's complete adjuvant in the chicken: efficient immunostimulation with severe local inflammatory reaction].

To quantify the enhancing activity of Freund's complete adjuvant (FCA), the humoral immune response of hens to the antigen human serum albumin (HSA) injected intramuscularly combined with FCA was measured. Local tissue reaction was examined on macroscopic and microscopic level. Other hens were injected with HSA in physiological sodium-chloride solution and served as controls. The immunization of hens without using FCA resulted in a short-term rise in immunoglobulin G (IgG) antibody titres, while the hens injected with HSA and FCA developed a long-term response (plateau-form of antibody titres). Local tissue reaction after injection of HSA in sodium-chloride solution was a mild and transient form of interstitial myositis. The immunization with HSA combined with FCA regularly resulted in a persisting granulomatous myositis. It is therefore a matter of animal protection to demand restricted use of FCA and to promote adjuvants of comparable efficiency, but better tolerance.

Animals↗

PubMed1995

[Intestinal absorption of homologous and heterologous immunoglobulin G in newborn calves].

Studying the prophylactic effects of specific yolk antibodies against diarrhea in newborn calves, also the intestinal absorption of unspecific heterogeneous avian antibodies as well as their effects on the uptake of maternal bovine colostral antibodies (bIgG) was investigated. Two groups of newborn calves received egg powder (16 g or 8 g per day) for the first 10 days of their life beginning with the first meal. A third group was kept as a control without any egg powder in their diet. Blood samples (5 to 10 calves per sampling time) were taken from 123 calves at 6, 12, 24, 48, or 96 h postnatally. With both doses the highest chicken IgG (cIgG) levels (3.1 micrograms resp. 1.2 micrograms per ml serum) have been measured 12 h after birth. These concentrations decreased continuously to the levels of 1.1 micrograms resp. 0.2 micrograms cIgG per ml serum at 96 h postnatally. The uptake into blood at 6 h postnatally has roughly been estimated as approximately 23% (bIgG) and 7% resp. 6% (cIgG) of the IgG dosages given with the first meal. The time-course (6 to 96 h) of the bIgG level in blood was quite stable, plateauing already after 6 h at a mean of 5.9 mg per ml serum. Significant differences between the bIgG levels of calves with yolk antibodies in their diet (6.2 resp. 6.1 mg bIgG per ml serum) and those of the control group (5.4 mg per ml serum) could not be observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1995

Comparative digestion in cattle and sheep fed wheat silage diets at low and high intakes.

Winter wheat (Triticum aestivum L.), harvested at late milk, early dough, and hard dough stages of maturity was ensiled for nutritive comparisons. Diets were adjusted to 13% CP with a soy protein concentrate and fed to six ruminally fistulated growing steers and nine adult wethers in a repeated 3 x 3 Latin square design to study the effects of maintenance and ad libitum intakes on digestibility of different feed fractions. At both intakes, digestion values for the steers were greater than or equal to those for the sheep for all feed fractions except CP. Wethers achieved greater intake per unit of BW than steers during ad libitum intake. Voluntary OM intakes of steers only differed between the milk stage diet and the dough stage diets. At low intake, the diets containing the more mature silage were more digestible. At high intake, the OM of diet containing the early dough stage silage ws most digestible. Increased intake caused a depression in digestibility of different feed fractions. The magnitude of the depression varied among diets and fractions. Data indicated that the nutritive value of diets based on whole crop wheat silage is affected by stage of maturity, animal species, and amount of intake. The assessment of the nutritive value of diets based on whole crop wheat silage should therefore be made with the animal species and at the amount of intake for which the diets are intended.

Animals↗

PubMed1994

Mammary and renal excretion of purine metabolites in relation to energy intake and milk yield in dairy cows.

This investigation was conducted to quantify the purine excretion of cows and to evaluate milk allantoin as an estimator of synthesis of microbial protein in the rumen. Concentrations in plasma of allantoin and uric acid and their excretion in urine and milk were determined using 16 Holstein cows at 21 to 315 d of lactation and yielding 8 to 36 kg/d of milk. The mean daily intake of a 55:45 roughage and concentrate diet was 16.3 kg of DM with 106 MJ of NEL and 13.8 to 16.0% CP. Total urine was collected over 24 h, plasma samples collected four times, and milk samples collected twice on the same day. Analyses of purine metabolites were performed with HPLC. On average, excretion of allantoin in urine and milk was about 294 and 4.1 mmol/d for allantoin and 35 and 1.1 mmol/d for uric acid. Excretion of allantoin in milk was correlated to concentration in plasma (r = .84). As milk yield increased, percentage of milk allantoin increased from .6 to 2.4% of total allantoin excretion (r = .85). The correlations of NEL intake with allantoin excretion in milk (r = .80) and in urine (r = .84) were similar. Daily milk yield was correlated with plasma allantoin (r = .78) and milk allantoin excretion (r = .95). We concluded that determination of milk allantoin is a useful, noninvasive method to monitor rumen microbial protein synthesis.

Allantoin↗

PubMed1994

[The influence of rumen metabolism on cyclic N compounds in the blood plasma of ruminants].

The purpose of this paper was to study the effect of rumen metabolism on the concentration of certain cyclic N-compounds in blood plasma. The plasma from two groups of lambs in the phase of rumen development during early and late weaning was used. As a second model, samples from steers fed at maintenance and after emptying of the rumen via cannula were used. Plasma samples were obtained from the jugular vein in regular intervals. The HPLC-technique was employed as analytical method. The plasma levels of allantoin and of hippuric acid increased about 2.2-3.7 fold and 2.4-6.4 fold in lambs during rumen development. They decreased to about 43% and 13% after emptying the rumen of steers. These metabolites appear to reflect rumen protein synthesis and fibre breakdown and are considered useful estimators of rumen function. Cytidine, uridine, uric acid and hypoxanthine were only influenced in part by rumen metabolism. Plasma pseudouridine was decreased and creatinine was increased in lambs in relation to body mass and remained unaffected in steers.

Animals↗

PubMed1990

[Effects of purine-rich nutrition on the renal and extrarenal excretion of purine catabolites in Dalmatian dogs].

In eight Dalmatian dogs exogenous effects (dietary purine, xylit infusion) on plasma uric acid were examined and relationships between purine intake and excretion were established. Increasing purine intake resulted in a linear increase in renal excretion of urate (r = 0.952) and a less steep increase of allantoin (r = 0.901). In pairs of two animals with low and high purine intakes the metabolic fluxes in steady state were measured by continuous infusion of (2-14C) urate. The extrarenal excretion rates of urate + allantoin during high-purine and low purine feeding averaged 2.9% and 8.5% of entry rates. The results are discussed in comparison with human data and a remarkably good agreement is observed.

Allantoin↗

PubMed1990

[The effect of glucocorticoid on the glucose metabolism of pigmy goats. 1. Selected metabolites of energy metabolism].

In order to study mechanisms in ruminants responsible for glucocorticoid-induced hyperglycemia the effects of a single intravenous dose of a glucocorticoid on energy metabolism were investigated by measuring plasma levels of glucose, lactate, free fatty acids (FFA), 3-hydroxybutyrate (3-HOB) and acetoacetate (AcAc). Experiments were performed on four castrated male African pygmy goats at two metabolic states: "fed" with a single daily meal of hey and "fasted" with starvation for 3 days. The untreated goats served as their own control. The glucocorticoid application to fed animals resulted in an increase in glucose level (+43%) lasting more than 11 h and an irregular increase of lactate. The concentration of 3-HOB was increased especially before feeding (+64%). In contrast, FFA were decreased (-27%) the second day after glucocorticoid application. In fasted goats the glucocorticoid also caused an increase in glucose level (+25%). The effect was smaller than in fed animals. Concentrations of FFA, 3-HOB and AcAc were 10, 20 and 35% lower than those of untreated goats. With regard to the antiketotic use of glucocorticoids the decrease of plasma levels of FFA and ketone bodies in starving animals is of special importance. Obviously the animals were able to use glucose again as a main energy source instead of FFA.

3-Hydroxybutyric Acid↗

PubMed1990

[The effect of glucocorticoids on glucose metabolism in pygmy goats. 2. Glucose turnover and recycling].

In the present study glucose kinetic parameters like pool size, distribution volume and rates of total entry and irreversible loss were determined in four castrated male African pygmy goats during hyperglycemia induced by an intravenous glucocorticoid injection (0.25 mg dexamethasone = DXM per kg body weight). Experiments were done at two different metabolic states, "fed" once daily and "fasted" after three days of starvation. The use of [U-14C]- together with [2-3H]- or [6-3H]-glucose made it possible to show changes in rates of gluconeogenesis, phosphorylation and specific recycling of glucose-C (e.g. lactate/alanine). During glucocorticoid induced hyperglycemia (+45%) in fed animals de novo synthesis of glucose (+5%) and lactate/alanine recycling increased (+4%). Rates of irreversible loss for all applied tracers in fasted animals formed only two thirds of the values of fed animals. During hyperglycemia (+40%) after DXM-injection de novo synthesis of glucose (+8%) and lactate/alanine recycling also increased (+27%). Furthermore the rate of phosphorylation of glucose decreased in fasted pygmy goats. The increase in availability of glucose both in fed and fasted animals is due to an increase in gluconeogenesis. In fasted animals additionally a decrease in the rate of phosphorylation and therefore of the peripheral glucose turnover has to be considered.

Animals↗

PubMed1989

Quantification and kinetics of purine catabolism in Dalmatian dogs at low and high purine intakes.

1. In eight Dalmatian dogs low and high purine intakes resulted in plasma urate levels from 25 to 185 mumol/l. 2. The relationship between purine intake and excretion of uric acid and allantoin per day was described by linear regression equations. 3. The elimination of endogenous purines was 1.8 mmol/day for urate and 1.7 mmol/day for allantoin. Exogenous purines increased renal excretion by 0.57 mmol/mmol. 4. Kinetic measurements with [2(-14)C]uric acid infused continuously into each of two dogs on low and high purine revealed increases of plasma pool (urate + allantoin) of 3.3 fold and entry rate of 4.0 fold. Conversion of urate into allantoin increased from 20 to 36%. 5. Renal elimination of catabolites increased 3.3 fold and exhalation rate of purine-CO2 379 fold. Extra-renal elimination at high purine intake was quantitatively similar to humans and closely related to pool size.

Allantoin↗

PubMed1986

The role of adipose and hepatic tissues in the lipogenesis of the dog.

In order to determine the main organ of fatty acid synthesis de novo in the dog, glucose-C incorporation into fatty acids and glucose-1-C oxidation to CO2 were measured by means of glucose-U-14C and glucose-1-14C in samples of adipose and hepatic tissues of 16 animals. For comparison of the two organs the data were referred to the respective DNA content. The rate of glucose-C incorporation into fatty acids of adipose tissue exceeded that of hepatic tissue about 1000-fold. Therefore, the adipose tissue is to be considered the almost exclusive organ of lipogenesis in the adult dog. Glucose-1-C oxidation and glucose-C incorporation in adipose tissue were correlated by r = 0.887. Consequences of these results may be of concern in model experiments using dogs.

Adipose Tissue↗

PubMed1985

[D(-)Lactic acid--a metabolism problem].

The metabolization of D-lactate was examined in volunteers by means of renal excretion after intake of DL-lactate, and in rats as well as in rat liver in vitro by the oxidation rate of 14C-D-lactate to 14CO2. In five volunteers after intake of DL-lactate containing 1.60 to 6.5 mmol D-lactate per kg 0.75 (equiv. to 50-200 mg/kg) an average of 1.2-2.2 percent of the dose was eliminated in urine. The exponential decline of renal elimination during the first 15 hours after intake and the total excretion time up to 24 hours (and possibly more) suggested a quite slow rate of metabolism. Following intraperitoneal injection of 2.0 and 4.2 mmol per kg 0.75 in rats (equiv. to 62 and 131 mg per kg in man) the oxidation rate of D-lactate vs. L-lactate was significantly and strongly reduced. After intragastral dosage of DL-lactate containing 4.2 to 12.8 mmol D-lactate per kg 0.75 an average of 0.9 and 2.4 percent were excreted in urine as D-lactate and as metabolites. Even after the lowest dose D-lactate oxidation to CO2 extended far beyond 8 hours. Higher doses decreased the rate of D-lactate oxidation. In tissue samples of rat liver in vitro oxalate, L-lactate and pyruvate inhibited the oxidation of D-lactate. L-lactate in a physiological concentration was sufficient to effect an inhibition of 20 percent. A significant increase of D-lactate oxidation with increasing body weight and a significantly higher oxidation of D-lactate in conventionals vs. germ-free rats indicated the influences of age and gastro-intestinal flora on D-lactate metabolism. From these results it is concluded that D-lactic acid is only slowly metabolized if the concentration of one or other of the lactate isomers is elevated.

Adult↗