Endogenous Fecal Excretion Research Articles

Stable Isotopic Measurement of Endogenous Fecal Calcium Excretion in Children

SummaryUsing a stable isotopic technique in which 42Ca was administered via a bolus injection, we measured endogenous fecal calcium excretion, Vf, in five healthy children, aged 3–14 years. The Vf averaged 1.4 ± 0.4 mg/kg/day, and was lower than urinary Ca excretion (Vu) in four of the five children. These results for Vf are consistent with previously reported results for Vf in healthy adults and much lower than those reported in premature infants. These results may be useful in understanding developmental changes in Ca metabolism and in interpreting dual tracer Ca isotope studies in children.

Measurement of endogenous fecal excretion and true absorption of selenium in dairy cows

A method combining balance techniques with an estimate of endogenous fecal selenium (Se) was evaluated as a measure of Se absorption in dairy cows. Endogenous fecal Se was estimated based on tracer enrichment in an index tissue (or fluid) that was assumed to represent enrichment of all endogenous sources of fecal Se. Two nonlactating Holstein cows fed a low-Se diet (0.035 mg Se kg−1 dry matter) were administered 4 mg Se-76, intraruminally, each day for 5 d (days 1–5). After a 10-d equilibration period, total collections of feces and urine were made at 24-h intervals for two 5-d periods (days 16–20 and days 21–25). On day 26 the animals were sacrificed and samples of all major tissues were collected. Samples were analyzed for total Se and Se stable isotope ratios. Selenium-76 enrichment was similar in tissues considered to be contributors to endogenous fecal Se, which supported the assumption that an index tissue could be used to estimate endogenous fecal excretion of Se. Endogenous fecal Se estimated from tracer enrichment in serum and liver was 22–36% of the total fecal Se excreted. True Se absorption was 10–16% of the daily Se intake. Key words: Selenium, stable isotope, tissue distribution, endogenous excretion, absorption, dairy cows

Equilibration of labelled and endogenous bile acids in patients with liver cirrhosis after administration of (24-14C)cholic and chenodeoxycholic acids

On separate occasions (24-14C)cholic acid and (24-14C)chenodeoxycholic acid were administered intravenously to patients with liver cirrhosis and the isotope excretion in urine and faeces monitored. Bile acids in serum, urine and faeces were extracted and separated into unconjugated bile acids, glycine- and taurine conjugates, glucuronides and sulphates. Individual bile acid conjugates were separated by high-performance liquid chromatography (HPLC) and the unconjugated bile acids were separated by gas-liquid chromatography (GLC) and identified by gas chromatography-mass spectrometry (GC-MS). Individual bile acid conjugates were quantified and their isotope contents determined. In serum, isotope contents declined rapidly during the first day, followed by a markedly slow rate of reduction. In accordance with this, the excretion of isotope from the patients was found to be very slow and the routes of bile acid excretion were changed, which resulted in an increased ratio of urine/faeces isotope excretion. Studies of the ratio of labelled to endogenous bile acid conjugates indicated that a continuous transformation of the labelled compounds occurred during the period of study. As judged from serum bile acids, conjugation to glycine- or taurine conjugates was rapid. The specific activities of labelled sulphate esters were consistently lower than for other conjugates during the 300-min observation period. During the first day, the urinary bile acids contained a high proportion of unconjugated labelled bile acids, which gradually disappeared. Labelled primary bile acids were slowly converted into microbial products, mainly 7-alpha dehydroxylated derivatives. The observed slow transformations resulted in a much delayed equilibration of labelled and endogenous bile acid derivatives, which invalidates isotope techniques for calculation of kinetic data of bile acid turnover. However, the observed very slow turnover of labelled bile acids in cirrhosis, owing to the persistent high rate of intestinal absorption and low capacity for urinary excretion, makes it possible for the intestinal flora to markedly change the composition of the bile acids in the pool. Studies of endogenous urinary and faecal bile acid excretion revealed the changed route of bile acid excretion with a high urinary/faeces ratio and the decreased synthesis of bile acids in cirrhosis.

Age-dependent Variation of Zinc-65 Metabolism in LACA Mice

Mice were gavaged with zinc-65 solution, 8.6-19.3 kBq per mouse, and the whole-body retention and organ content of zinc-65 were measured at different times after administration. The age-dependence of the fractional absorption of zinc-65 from the gastrointestinal tract (f1), the endogenous faecal excretion fraction of zinc-65 (EFEF), tissue distribution and whole-body retention were determined. The f1 values obtained were 0.86 +/- 0.15, 0.64 +/- 0.11, 0.52 +/- 0.07 and 0.39 +/- 0.02 in suckling, adolescent, young adult and older mice, respectively. The EFEF values determined were 0.083 +/- 0.008, 0.099 +/- 0.004, 0.122 +/- 0.018 and 0.144 +/- 0.005 of intraperitoneally injected zinc-65 in suckling, adolescent, young adult and older mice at administration. Zinc-65 mainly distributed in the liver, muscle, lung, kidneys and bone. In some tissues, there was an inverse relationship between the relative content of gavaged zinc-65 and the animal's age at administration. The whole-body biological half-lives of zinc-65 increased with animal age. The influence of the age-dependent variation of zinc-65 metabolism on internal dose and on radiation protection is discussed.

COMPARISON OF FORAGE DIGESTION BY CATTLE AND HORSES

Two trials compared digestion of Saskatchewan-grown hays by cattle and horses. In the first study, Altai wildrye (Leysum angustus Trin.), smooth bromegrass (Bromus inermus Leyss.), crested wheatgrass (Agropyron cristatum L.), Kentucky bluegrass (Poa pratensis L.), oat hay (Avena sativa L.) and reed canarygrass (Phalaris arundinaceae L.) hays were fed to six beef steers and six crossbred geldings. The second study compared alfalfa hay (Medicago sativa L.) to dehydrated alfalfa pellets. Voluntary dry matter intake (VDMI) of hay by cattle was related to neutral detergent fiber content (R2 = 0.66). No single nutrient reliably predicted VDMI by horses. Cattle and horses had the highest VDMI for bromegrass hay in trial 1. Cattle had similar intakes of dehydrated alfalfa pellets and alfalfa hay, but horses ate 17% more (P < 0.05) hay than pellets. Cattle digested 28–82% more (P < 0.05) fiber from grass hays than horses which may account for their higher dry matter (DM) digestion of these hays. Cattle and horses utilized legume feeds similarly. Energy intakes of all animals exceeded maintenance except for cattle fed reed canarygrass hay. True crude protein digestibility and metabolic fecal protein of forage-fed cattle and horses were estimated at 83.4 and 80.3%, and 2.67 and 2.17 g 100 g−1 DM intake, respectively. Horses had higher true digestibilities of Ca (75%) than P (33%) but cattle digested more P (76%) than Ca (32%). Endogenous fecal Ca excretion for cattle and horses were assessed at 6.5 and 22.1 mg kg−1 body weight (BW), respectively, while endogenous fecal P excretions were 13.3 and 10.2 mg kg−1 BW, respectively. Key words: Horse, cattle, legume, grass, crude protein, fiber

Phosphorus and calcium metabolism in growing calves with special emphasis on phosphorus homoeostasis. 4. Studies on milk-fed calves given different amounts of dietary phosphorus but a constant intake of calcium

SUMMARYFriesian bull calves, 2 weeks old, were given an experimental diet of cow's milk supplemented with phosphorus to provide three rates of P intake: adequate, high, and very high. After 1 week's preliminary feeding, studies of absorption, endogenous secretion, urinary excretion, serum concentration, retention and kinetics of Ca and P metabolism were made by a balance and dualradioisotope technique with 32P and 45Ca.The efficiency of P absorption decreased significantly as the P intake increased and the highest absorption efficiency was 96% on the unsupplemented milk diet. Endogenous faecal excretion of P was low on all treatments. Urinary P excretion was substantial even on the milk-only diet and increased further with supplementation of P. The efficiency of absorption of Ca remained constant, and urinary Ca excretion was low in all the groups. Serum P and Ca concentrations did not vary significantly but there was a significant decrease in the retention of P and Ca as the P intake increased.Although urinary excretion appears to be the main process responsible for P homoeostasis in preruminant milk-fed calves, some regulation of the efficiency of absorption of P according to the P intake may also occur.

Endogenous losses of phosphorus by sheep

SUMMARYTwelve sheep were fed semisynthetic roughage diets at three rates to study the effects of intake of dry matter, concentration of phosphorus and the physical form of two low-P barley straws upon the faecal losses of P. The sheep were in negative P balance throughout the experiement. The absorption of dietary P increased with P intake and was unaffected by differences in the physical form of the roughage. For each barley straw diet, endogenous faecal P increased with dry matter intake, and was higher when the roughage was ground than chopped. Over the whole experiment, daily endogenous faecal P ranged from 8·5 to 31·5 mg/kg live weight. Endogenous faecal P was related to P intake or to dry matter intake and plasma inorganic P. The concentration of faecal endogenous P was negatively related to the intake of each diet. It is concluded that the concentration of inorganic plasma P and the rate of salivary secretion are responsible for the endogenous faecal excretion of P and the regulation of P balance in sheep fed low-P diets.

Measurement of Calcium and Phosphorus Fluxes During Lactation in the Rat

Novel, two-compartment metabolic cages for rats were constructed to examine Ca and P fluxes during lactation. Four consecutive balance studies of 4 d each were performed in lactating rats and nonlactating controls. Lactating rats had dramatically higher intestinal absorptions of Ca and P resulting from both increased food consumption and elevated fractional absorptions of these elements. Urinary Ca excretion was reduced during lactation whereas urinary P excretion was unchanged. Endogenous fecal Ca excretion (determined by infusing 45Ca and dividing fecal 45Ca content by urinary 45Ca specific activity) was similar in lactating and nonlactating rats. In a separate study, pup retention of ingested Ca averaged 96%. Therefore, the difference in pup carcass Ca content between d 1 and 17 of age is assumed to equal 96% of the Ca transfer rate into milk. Similar calculations were applied to P. Milk transfer rates were determined to be 126 and 99 mg/d for Ca and P, respectively. These calculations indicate that 19% of the Ca transferred to milk was derived from the maternal skeleton with the maternal diet supplying the remaining Ca. This study provides the first comprehensive analysis of the alterations in Ca and P fluxes that occur during lactation in the rat.

Effect of physical activity on calcium and phosphorus metabolism in the rat

Changes in skeletal mass, nutritional calcium and phosphorus balance, and intestinal calcium absorption were studied in four groups of rats: control, exercise allowing free access to food, exercise with pair-feeding to control levels, and immobilization. The exercise regimen consisted of treadmill running 25 m/min, 60 min/day, 5 days/wk for 13 wk; rats were immobilized by bilateral sciatic denervation. The total body Ca (TBCa) was measured by neutron activation analysis as an index of skeletal mass. Standard metabolic balance techniques were used to determine calcium and phosphorus balance, and an in situ duodenal loop ligation preparation was used to study the active and passive intestinal Ca transport processes. Exercise promoted a positive Ca and P balance and increased the skeletal mass, largely as a result of an increase in 1,25-dihydroxyvitamin D and an enhancement of the intestinal Ca absorption efficiency. Urinary excretion of Ca and P did not differ from control levels and food intake was not a factor because pair-fed rats responded to exercise almost identically to those fed ad libitum. Conversely, immobilization caused a decrease in TBCa and a lower Ca and P balance. These effects are the result of an increased urinary mineral excretion, greater endogenous fecal excretion, and decreased mineral absorption efficiency in the intestine.

True absorption and endogenous fecal excretion of manganese in relation to its dietary supply in growing rats

A conventional balance study with 48 male weanling rats was conducted to determine true absorption and endogenous fecal excretion of manganese (Mn) in relation to dietary Mn supply, following the procedures of a previously adapted isotope dilution technique. After 10 d on a diet with 1.5 ppm Mn, eight animals each were assigned to diets containing 1.5, 4.5, 11.2, 35, 65, or 100 ppm Mn on a dry-matter basis. Three days later, each rat was given an intramuscular(54)Mn injection and kept on treatment for a balance period of 16 d.Apparent Mn absorption assessed for the final 8 d, averaged 8.6 μg/d without significant treatment effects, although Mn intake ranged from 18.6 to 1200 μg/d, in direct relation to dietary Mn concentrations. Mean fecal excretion of endogenous Mn for the six treatments was 0.9, 2.7, 7.4, 11.0, 16.3, and 17.7 μg/d, respectively. These values delineate the rates to which true absorption exceeded apparent rates. True absorption, as percent of Mn intake, averaged 28.7, 15.9, 11.7, 6.1, 3.4, and 2.0, respectively, as compared with mean values of 23.9, 10.9, 6.2, 3.4, 1.2, and 0.5 for percent apparent absorption. It was concluded that both true absorption and endogenous fecal excretion markedly responded to Mn nutrition and that the reduction in the efficiency of true absorption was quantitatively the most significant homeostatic response for maintaining stable Mn concentrations in body tissues.

The effect of phosphorus on endogenous fecal calcium excretion in man

The effect of phosphorus on the endogenous fecal calcium excretion was investigated in man by administering tracer doses of 47Ca intravenously in control studies and during phosphorus supplementation. The phosphorus intake was ∼800 mg/day in control studies and 2000 mg during phosphorus supplementation of the constant diet The studies were carried out during different calcium intake levels of ∼200, 800, 1300, 2000, and 2600 mg/day. Following the dose of 47CaCl2, the values of the plasma levels, urinary, and fecal excretions of 47Ca were used to calculate the endogenous fecal calcium. None of these values differed significantly during phosphorus supplementation from those in corresponding control studies, irrespective of the calcium intake. During addition of phosphorus to the different calcium intakes, a consistent finding was a significant decrease of the urinary calcium and a slight, but not significant increase of the fecal calcium except during the 800 mg calcium intake.

The effect of dietary intake of calcium and dry matter on the absorption and excretion of calcium and phosphorus by growing lambs

SUMMARYThe isotope dilution technique was used to measure endogenous faecal excretion and absorption of dietary Ca and P by growing lambs. Groups of four lambs were given 0·8 or 1·2 kg/day of a pelleted barley and soya-bean diet containing 4·2 g P/kg D.M. and supplemented to contain 1·79, 3·52 or 4·67 g Ca/kg D.M.At the lowest dietary concentration of Ca, absorption of Ca was insufficient to meet the Ca required for deposition in the newly formed bone matrix of the skeleton; retention was 0·39, 1·16 and 1·12 g/day with increasing dietary Ca concentration. The proportion of dietary Ca absorbed decreased (P < 0·001) with increasing Ca intake, ranging from 0·85 to 0·44. Endogenous faecal excretion of Ca was independent of the absorption of dietary Ca, but increased (P < 0·05) from 17·2 at the lower to 21·1 mg/kg live weight/day at the higher D.M. intake. Plasma concentration of Ca was higher for the female (2·51) than the male (2·33 mmol/1) lambs and increased linearly (P < 0·001) with dietary concentration of Ca from 2·31 to 2·52 mmol/l.The retention of P increased with Ca and D.M. intake. On the other hand, the proportion of dietary P absorbed (0·85) was independent of Ca intake and hence of P retention. Increases in P retention were reflected by decreases in urinary P, but not in endogenous faecal excretion. Endogenous faecal excretion of P increased with D.M. or P intake from 17·9 at the lower to 33·5 mg/kg live weight/day at the higher intake.The results are discussed in relation to dietary allowances of Ca and the mechanism of P homoeostasis.

Bioavailability of Calcium in Heat‐Processed Milk

ABSTRACTBioavailability to rats of calcium in milk subjected to the DASI Free Falling Film system (UHT) of pasteurization was compared with the bioavailability of the mineral in raw, high temperature‐short time pasteurized, and stored UHT milks. In two other studies, the calcium in the milks was equilibrated with 47Ca. Intestinal absorption (both uncorrected and corrected for endogenous fecal excretion) and femoral deposition of calcium were measured. In another study, femur calcium was determined in rats deriving calcium and phosphorus exclusively from the milks. No significant effects were attributable to heat treatment.

Prediction of response of blood lead to airborne and dietary lead from volunteer experiments with lead isotopes.

To predict the response of blood lead to airborne and dietary lead requires knowledge of the rate of uptake of lead into the body from lung and gut, its subsequent partitioning between compartments, the stay time in those compartments, and its redistribution or excretion. Tracer studies with volunteers have shown no differences in systemic distribution of inorganic lead between tissues whether it is taken by inhalation, ingestion or injection. Lead is rapidly transferred from plasma to red cells, and there is slower movement thence into liver and other soft tissues, to bone, and to excreta. Work at Harwell and elsewhere with 203Pb has shown that the initial rapid distribution leaves rather over half the assimilated lead attached to red cells. The result is remarkably consistent, and applies also to dogs and baboons. The renal clearance (Vu) (ratio of U to CB, or daily urinary output expressed as mass of blood having the same lead content), and also the endogenous faecal clearance excretion rate (Vf), have been measured on human subjects with 203Pb. The results are consistent with Vu, as measured with stable lead, with many results giving Vu about 0.1 kg d-1. However, there is evidence that Vu increases when CB is elevated above the normal. This may explain the nonlinear relation between uptake of lead and the corresponding CB, which has been observed in humans exposed to environmental lead. Vf is about half Vu, and a similar result applies to calcium. The clearance rate Va of 203Pb from blood to bone has been measured, and a variety of human and animal data in the literature has been reviewed to support this result. Combined with bone turnover rates (from data on 90Sr), the postulated inputs to bone give estimates of skeletal burdens which agree with post-mortem results. The results are combined in a compartment model. The retention of lead aerosol in the lung, and uptake from the gut are then considered, with use made of radioactive tracer (203Pb), stable isotopic tracer (204Pb) and total lead measurements. Here there is great diversity of results. Particle size affects the fractional lung retention and the site of retention, which in turn affects the fractional uptake to blood. Presence or absence of food in the stomach when lead is ingested greatly affects the fractional gut uptake. Finally, a limited selection of results of volunteer exposures to stable lead in air or diet are reviewed.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium metabolism of intact and thyroparathyroidectomized rats fed a bicarbonate enriched diet

Rats fed a bicarbonate-enriched diet become alkalotic during their feeding period (ca. 10 h/day). Alkalosis produced a significant reduction in the plasmatic concentration of ionized calcium and increased parathyroid hormone secretion confirmed by concurrent hypophosphatemia and increased urinary excretion of cAMP. Three weeks of treatment produced, however, a significant reduction of bone Ca resorption. The increased endogenous fecal excretion of calcium counteracted the enhancement of true calcium absorption. No significant change in the skeletal calcium mass was observed. Thyroparathyroidectomized rats fed the alkaline diet reduced further their rate of bone Ca resorption and increased significantly their skeletal calcium mass.

GENETIC CONTROL OF PHOSPHORUS METABOLISM IN SHEEP

Balance studies with chimaera-derived sheep have provided good evidence for genetic control of phosphorus metabolism. Plasma concentrations, urinary and endogenous fecal excretion and efficiencies of absorption of P were similar within but different between four sets of triplets. The results were confirmed with a larger group of chimaera. Key words: Chimaera, sheep, phosphorus, genetics, metabolism

Skeletal retention of45Ca and85Sr compared: Further studies on intravenously injected85Sr as a tracer for skeletal calcium

The physical characteristics of47Ca and45Ca make them unsuitable for studying the long-term (>30 days) handling of skeletal calcium in patients. Therefore a study was conducted in 3 normal subjects in which the skeletal uptakes and subsequent retentions of simultaneously administered intravenous doses of45Ca and85Sr were compared. Specific activities of45Ca (relative to40Ca) were then observed in plasma and prolonged urine collections for up to 5 months. The whole-body retention of85Sr was followed simultaneously in a whole-body counter. On the hypothesis that the single passage retention of both tracers in the skeleton was identical, after the effects of second and subsequent tracer recirculations the skeleton had been removed by deconvolution analysis, it was possible to calculate from the85Sr data and the excretory clearance of40Ca the predicted45Ca specific activity for each subject as a function of time. Within the limits imposed by data scatter and measurement uncertainties, the predicted and observed long-term45Ca specific activity curves appeared identical. However, in a separate study on approximately 40 patients,85Sr was shown to underestimate the size of the exchangeable pools of bone calcium by about 20%. In the same group of patients, a close relationship was observed between the endogenous fecal calcium excretion rates, as calculated, respectively, from data obtained after simultaneous injections of85Sr and47Ca. Furthermore, the47Ca accretion rate to bone could be predicted from the85Sr data with a coefficient of variation of 15%.85Sr is not the preferred tracer for studying the short-term handling of calcium by the skeleton. However, long-term “exchange” processes lead to prolonged (>30 days) tracer retention at surfaces where new bone is not being formed. When it is necessary to separate these processes from true bone formation,85Sr is a practical and suitable tracer for patient studies.

The long-term effects of pancreatectomy on the Ca metabolism of the rat.

The Ca metabolism of pancreatectomized (PX) rats was investigated three months after surgery. Most PX animals were in negative Ca balance because of increased endogenous fecal Ca excretion and reduced true Ca absorption. Significant increases were also observed in bone Ca resorption rates, hydroxyproline excretion and size of osteocyte lacunae. Inverse correlations between the rates of bone Ca resorption and Ca balance were observed in the PX and control groups. Significantly, both correlations were found to fit the same function. It was concluded that parathyroid hormone secretion and its metabolic expression were not impaired by pancreatectomy. The coupling between bone Ca accretion and resorption was absent in PX animals: high resorption rates were found associated with normal or decreased accretion rates. These latter rates, in combination with the negative Ca balance, explain the reduction in the skeletal Ca mass.

Absorption and secretion of calcium and phosphorus in the alimentary tract of lambs infected with daily doses of Trichostrongylus colubriformis or Ostertagia circumcincta larvae

The flows of endogenous and exogenous calcium and phosphorus in the digesta at the abomasum, ileum and in the faeces were measured in growing lambs infected daily with 3000 T. colubriformis larvae (TC), 5000 O. circumcincta larvae or no larvae. The lambs were given 0·70 or 1·0 kg per day of a pelleted diet and the flow rates were measured by reference to soluble and particulate radioactive markers. The fraction of Ca and P in digesta of endogenous origin was measured by the method of isotope dilution involving a single intravenous dose of 45Ca or 32P. Ostertagia circumcincta infection was without effect on the absorption and secretion of Ca and P in the digestive tract, other than producing a small but significant increase in the endogenous faecal Ca excretion. There was, however, a striking increase in the flow of digesta at the abomasum, the DM and Na content of which was consistent with an increased secretion from the mucustype cells in the abomasal mucosa. The extra digesta was absorbed in the small intestine. Trichostrongylus colubriformis infections reduced the absorption of exogenous P by about 30 per cent and increased losses of endogenous P due to the action of worms on the mucosa of the small intestine. The net effect of this was to induce a P deficiency in TC lambs, leading to a reduced flow of salivary P and a reduction in the plasma concentrations of P. The effect of TC on Ca metabolism was limited to an increase in endogenous faecal excretion.

The phosphorus requirements for growth and maintenance of sheep

SUMMARYPhosphorus requirements for maintenance and growth were assessed by giving to growing lambs and non-pregnant ewes diets low in P and to growing lambs a diet containing the quantity of P recommended by the Agricultural Research Council (1980).Seven 14-week-old lambs were given ad libitum a pelleted diet containing 1·88 (LP) or 2·75 (NP) g P/kg D. M. for 13 weeks. There was no effect of P intake on feed intake or growth during the first 8 weeks when the P intake of the LP groups was 1·07 of Agricultural Research Council (1980) requirements. During the last 5 weeks the P intake of the LP group was only 0·87 of Agricultural Research Council (1980) requirements and growth and feed intake were higher in the male but not female lambs in the NP group. From the 3rd week the plasma concentration of P was significantly lower (P <0·001) in the LP group. Mineralization of selected bones was less in the LP group.After 14 weeks on the diet, balance trials with 32 P were carried out on the lambs from each dietary group. P intakes ranged from 1 to 3 g/day. An additional balance trial was undertaken with eight 2-year-old female sheep consuming a hay diet (1·5 g P/day).The endogenous faecal excretion of P by the growing lambs on the LP diet and ewes was 12·2 ± 0·8 and 12·7 ± 1·00 mg/kg live weight/day respectively, very close to the value (12 mg/kg live weight/day) adopted by the Agricultural Research Council (1980). The absorbability of the P in the concentrate and hay diets was 0.71 ±0·267 and 0·74 ± 0·0218 respectively, the former agreeing with and the latter higher than the corresponding value for Agricultural Research Council (1980).