Distinct alkaline phosphatase in serum of patients with lymphatic leukemia and infectious mononucleosis.

A distinct alkaline phosphatase (phosphatase N) was demonstrated in the serum of patients with acute lymphatic leukemia, chronic lymphatic leukemia, and infectious mononucleosis. This enzyme closely resembles that extracted from the thymus of mice with lymphoma or lymphatic leukemia, both in its electro-phoretic mobility and its substrate specificity. The phosphatase N activity was related to the clinical state of patients with lymphatic leukemia and disappeared with recovery from infectious mnononucleosis.

Intestinal transport of sugars and amino acids in diabetic rats.

The specificity and mechanism of altered intestinal transport of diabetic rats was studied with an everted ring technique. Increased intracellular accumulation of amino acids, as well as galactose and 3-O-methylglucose, was demonstrated in diabetes. The greater accumulation by diabetic intestine could not be attributed to a direct effect of the agent used to induce diabetes or to an alteration in food consumption. Although the changes were related to the severity of diabetes and could be reversed with treatment with insulin, they could not be modified by addition of insulin in vitro. The changes could not be induced in control intestine either with hyperglycemia from glucose infusion or preincubation with glucose in vitro. Although the higher concentration gradients of amino acids, galactose, and 3-O-methylglucose could result from increased energy utilization by diabetic intestine, an alteration of cell membrane function, as well, is suggested by the demonstration with kinetic studies of increased influx with an increase in V(max).

Inhibition of folate enzymes by sulfasalazine.

Sulfasalazine (salicylazosulfapyridine), an agent widely used for the treatment of ileitis and colitis, is also a competitive inhibitor of intestinal folate transport (1, 2). The mechanism of action of sulfasalazine remains uncertain. To further explore the mechanism of sulfasalazine action, the interaction of the drug with the folate recognition site was tested with three enzymes: dihydrofolate reductase, methylenetetrahydrofolate reductase, and serine transhydroxymethylase, each catalyzing a reaction involving a different folate derivative. Each of these enzymes was inhibited by sulfasalazine in the same concentration range as that previously observed to inhibit intestinal folate transport; the kinetic data are consistent with a competitive mode of inhibition. Specificity of inhibition was demonstrated by the finding that the reduction of the pteridine ring of pteroylheptaglutamic acid by dihydrofolate reductase was subject to inhibition, whereas the hydrolysis of the gamma-glutamyl peptide side chain by chicken pancreas conjugase was not affected. These results are interpreted to indicate that sulfasalazine interferes with a folate recognition site which is common to these enzymes and to the intestinal transport system. Sulfasalazine, therefore, has certain properties of an antifolate drug.

Rheumatoid cachexia: cytokine-driven hypermetabolism accompanying reduced body cell mass in chronic inflammation.

The cytokines IL-1 beta and TNF-alpha cause cachexia and hypermetabolism in animal models, but their role in human inflammation remains controversial. The relationship between in vitro cytokine production and metabolism was examined in 23 adults with RA and 23 healthy control subjects matched on age, sex, race, and weight. Body composition was measured by multicompartmental analysis of body cell mass, water, fat, and bone mass. Resting energy expenditure (REE) was measured by indirect calorimetry. Cytokine production by PBMC was measured by radioimmunoassay. Usual energy intake, physical activity, disability scores, medication use, and other confounders were also measured. Body cell mass was 13% lower (P < 0.00001), REE was 12% higher (P < 0.008), and physical activity was much lower (P < 0.001) in subjects with RA. Production of TNF-alpha was higher in RA than controls, both before and after stimulation with endotoxin (P < 0.05), while production of IL-1 beta was higher with endotoxin stimulation (P < 0.01). In multivariate analysis, cytokine production was directly associated with REE (P < 0.001) in patients but not in controls. While energy and protein intake were similar in the two groups and exceeded the Recommended Dietary Allowances, energy intake in subjects with RA was inversely associated with IL-1 beta production (P < 0.005). In this study we conclude that: loss of body cell mass is common in RA; cytokine production in RA is associated with altered energy metabolism and intake, despite a theoretically adequate diet; and TNF-alpha and IL-1 beta modulate energy metabolism and body composition in RA.

Multivitamin use and B vitamin status in a homebound elderly population.

OBJECTIVE: Homebound elderly are at increased risk for micronutrient deficiencies and nutritional status in this population has not been adequately described. There is evidence for beneficial effects of multivitamin use and a greater understanding of their nutritional contribution could identify behaviors that may help alleviate excess chronic disease. The purpose of this analysis is to investigate, in a racially diverse group of homebound elders, the association of multivitamin use with measures of plasma B vitamin concentrations. DESIGN: We examined the cross-sectional association between multivitamin use and plasma concentrations of B vitamins and homocysteine in 236 white and 182 black homebound elders (65-99y). Dietary intake was assessed and demographic and health information was ascertained. RESULTS: White and black elders had a high prevalence of dietary intakes below the Estimated Average Requirement for folate (38.1 and 40.7%), vitamin B6 (16.9 and 19.2%.), and vitamin B12 (3 and 3.9%) respectively. Multivitamin use was associated with higher mean plasma B vitamin concentrations in each group. In whites, multivitamin users had higher concentrations of vitamin B6 (64.6 vs. 32.4 nmol/L; p < 0.001), vitamin B12 (398 vs. 324 pmol/L;p < 0.001) and folate (39.4 vs. 30.4 nmol/L;p < 0.001). Black multivitamin users had higher concentrations of vitamin B6 (53.7 vs. 29.5 nmol/L; p < 0.001), B12 (427 vs. 372 pmol/L; p < 0.05) and folate (35.7 vs. 25.4 nmol/L; < 0.001) than non-users. CONCLUSIONS: Multivitamin supplementation was associated with higher mean plasma concentrations of vitamins B6, B12, and folate and lower prevalence of low plasma B vitamin status in a biracial homebound elderly.

B-Vitamin Therapy for Kidney Transplant Recipients Lowers Homocysteine and Improves Selective Cognitive Outcomes in the Randomized FAVORIT Ancillary Cognitive Trial.

BACKGROUND: Objectives: Elevated plasma total homocysteine (tHcy) is associated with increased risk of cardiovascular disease, stroke and dementia. Results of clinical trials using B-vitamins to reduce the cognitive risks attributed to tHcy have been inconsistent. The high prevalence of both hyperhomocysteinemia and cognitive impairment among kidney transplant recipients makes them an important population in which to evaluate the effect of lowering homocysteine on cognitive function. We therefore evaluated whether B-vitamin therapy to lower tHcy would prevent cognitive-decline in a cohort of stable kidney transplant recipients. DESIGN: The study was a longitudinal ancillary of the FAVORIT trial, a randomized, placebo-controlled multi-site trial of high-dose B vitamins to reduce cardiovascular and cerebrovascular events in clinically stable kidney transplant recipients with elevated tHcy. PARTICIPANTS: 584 participants from 18 sites across North America. INTERVENTION: The intervention consisted of a daily multivitamin containing high-doses of folate (5.0 mg), vitamin B12 (1.0 mg) and vitamin B6 (50 mg). The placebo consisted of a daily multi-vitamin containing no folate and recommended daily allowances of vitamins B12 and B6 (0 mg folate; 2.0 µg vitamin B12; 1.4 mg vitamin B6). MEASUREMENTS: Annual neuropsychological assessment for up to 5 years (mean 3.3 years) using a standardized test battery. Efficacy was analyzed on an intention-to-treat basis using end-of-trial data. Subgroup analyses included stratification for baseline plasma B-vitamin and tHcy concentrations. RESULTS: At baseline, cognitive impairment was common with 61% of participants falling more than one standard deviation below published norms for at least one cognitive test. Fewer than 1% of participants had insufficient plasma folate < 5 ng/ml or vitamin B12 < 148 pmol/L. However, 44.6% had plasma B6 concentrations < 30 nmol/L. At follow-up, processing speed and memory scores were modestly but significantly better in the B-vitamin supplement group than in controls (p≤0.05). There was no interaction between baseline tHcy, B-vitamin status and treatment on the cognitive outcomes. CONCLUSIONS: High-dose B-vitamin supplementation provided modest cognitive benefit for kidney transplant recipients with elevated baseline tHcy. Since nearly all participants were folate and vitamin B12 sufficient at baseline, the potential cognitive benefits of folate and B12 supplementation in individuals with poor B-vitamin status remains to be determined.

Folate deficiency enhances the development of colonic neoplasia in dimethylhydrazine-treated rats.

In patients with ulcerative colitis, epidemiological work has suggested an association between low folate status and an increased risk of colonic neoplasia. The aim of the present study was to determine if experimental folate deficiency increases the likelihood of developing neoplasia in rats treated with the carcinogen dimethylhydrazine. Weanling male Sprague-Dawley rats were fed with an amino acid-defined diet containing either 8 or 0 mg/kg folic acid. After 5 weeks of defined diet, weekly s.c. injections of dimethylhydrazine (20 mg/kg) were administered to both groups. Serum, whole blood, liver, and colonic folate concentrations at the time of sacrifice were significantly lower in folate-depleted animals (P less than 0.001). There were significant differences in the incidence of colonic neoplasia between the two groups after 20 weeks of dimethylhydrazine exposure: folate-deficient rats had a greater incidence of dysplasia (6 of 7 versus 2 of 7 animals; P less than 0.05) and carcinoma (6 of 7 versus 1 of 7 animals; P less than 0.01). Furthermore, a significantly greater proportion of folate-replete rats than folate-deficient rats were free of neoplastic lesions (5 of 7 versus 0 of 7 animals; P less than 0.05). These results suggest that, in this animal model, folate deficiency increases the risk of malignancy when there is an underlying predisposition to colorectal cancer.

Effect of anions on folate binding by isolated brush border membranes from rat kidney.

The characteristics of folate binding by brush border membranes from rat kidney homogenates were investigated. At pH 7.4, binding of [3',5',9-3H]-pteroylglutamic acid to membranes containing endogenous folate is inhibited by anions, with chloride being most effective followed by bromide, thiocyanate, iodide, phosphate and sulfate. A maximum inhibition of 70-75% is attained at a concentration of 0.1 M chloride and an incubation time of 30 min. The inhibition diminishes with increased incubation time and at 24 h is negligible. The binding of [3',5',9-3H]pteroylglutamic acid to brush border membranes stripped of endogenous folate by acid treatment is not inhibited by anions. Anion sensitivity can be restored to these treated membranes by reconstitution with membrane-derived folate, particularly 5-methyltetrahydropteroyl-glutamic acid, or by preincubation with synthetic 5-methyltetrahydropteroyl-glutamic acid. Inhibition of [3',5',9-3H]pteroylglutamic acid binding by anions in membranes with endogenous folate is best explained by an anion-induced stabilization of endogenous folate-binding protein complex resulting in a decreased rate of exchange with exogenous [3',5',9-3H]pteroylglutamic acid.

The reaction of tris (hydroxymethyl) aminomethane with calf intestinal alkaline phosphatase.

The effect of tris (hydroxymethyl) aminomethane concentrations on the rate of calf intestinal alkaline phosphatase-catalyzed hydrolysis of p-nitrophenyl phosphate was studied, in the pH range 8-10, where no transphosphorylation reaction could be detected. Kinetic analysis of the results permitted description of the effect of Tris concentrations T on the rate of enzyme catalyzed hydrolysis (V) by the following equation: (see article). The rate-accelerating effect of Tris concentrations can be ascribed to two different mechanisms: At moderate Tris concentrations (0.01-0.20 M) the enzyme forms a reversible addition complex with a Tris molecule. This complex has an enhanced catalytic activity. We suggest that the binding of Tris to the enzyme could potentiate a second active site of the enzyme, due to its ionization effect upon an acidic group of the enzyme of pK = 8.9. The modest linear rate accelerating effect of Tris at high concentrations (0.20-0.60 M) could be ascribed to the change of the dielectric constant of the medium, the degree of solvation of the protein, or change in the tertiary structure of the enzyme.

Carrier affinity as a mechanism for the pH-dependence of folate transport in the small intestine.

A mildly acidic pH in the lumen of the small intestine markedly enhances the transport of folate. This study investigated the relationship between pH and the affinity between folic acid and the apical membrane transporter using brush border membrane vesicles from rat jejunum and differentiated monolayer cultures of the colon carcinoma cell line, CaCo-2. Uptake studies with BBMV were conducted at folic acid concentrations of 0.1 to 50 mumol/l, conditions which were suitable for analyzing uptake data based on the Michaelis-Menten equation modified to include a nonsaturable component. These analyses yielded apparent Km values of 0.6 and 12.3 microM at pH 5.5 and pH 7.4, respectively (P less than 0.05). Values for Vmax were lower at pH 5.5 than at pH 7.4 (0.8 vs. 1.6 pmol/mg protein per 10 s, P less than 0.05). The studies with CaCo-2 cells employed folic acid concentrations of 0.1 to 5 mumol/l. Under these conditions the apparent Km for folic uptake was lowest at pH 6.0, where the Km was 0.7 mumol/l. The apparent Km increased sharply as a neutral pH was approached; reaching a value of 13.9 mumol/l at pH 7.1. These data suggest that the prominent pH effect on intestinal folate transport is, in part, explained by an increased affinity of the folate substrate for its membrane transporter.

Plasma homocysteine and parental myocardial infarction in young adults in Jerusalem.

BACKGROUND: A causal role for mildly elevated plasma homocysteine (tHcy) in cardiovascular disease remains undetermined. To address the unresolved issue of the antecedent-consequent directionality of the relationship, we assessed the familial association of tHcy with parental myocardial infarction (MI) in young Israeli men and women. We also compared tHcy concentrations in Jerusalem, where rates of coronary heart disease (CHD) are high, with the United States Third National Health and Examination Survey (NHANES III). METHODS AND RESULTS: A total of 8646 17-year-olds and 6952 parents were examined from 1976 to 1979 in Jerusalem. At ages 28 to 32 years, offspring of parents who experienced a documented MI during a 10-year follow-up (n=133 men, 62 women; 72% response) and offspring of CHD-free parents (n=389 men, 208 women; 71% response) were reexamined. tHcy levels were determined by the same laboratory for the NHANES non-Hispanic white population aged 25 to 34 years (n=379) and the Jerusalem population sample (n=858). Men from Jerusalem, but not women, had clearly higher tHcy levels than the sample from the United States (90th percentile, 23 versus 14 micromol/L). This difference was largely attributable to lower plasma vitamin B12 levels in the Israeli population. Male case offspring had higher adjusted tHcy than did controls (1.9 micromol/L, P=0.002). Logistic modeling revealed a graded increase in risk of parental MI across quintiles of offspring tHcy, with an adjusted odds ratio of 2.7 in the 5th quintile (P=0.0026 for trend). CONCLUSIONS: The higher tHcy in young male offspring of parents with CHD suggests that elevated tHcy precedes manifestation of CHD. The elevated population tHcy in men may contribute to the high incidence of CHD in Israel.

Low circulating vitamin B(6) is associated with elevation of the inflammation marker C-reactive protein independently of plasma homocysteine levels.

BACKGROUND: Lower vitamin B(6) concentrations are reported to confer an increased and independent risk for cardiovascular disease (CVD). The mechanism underlying this relationship, however, remains to be defined. Other diseases, such as rheumatoid arthritis, are associated with reduced vitamin B(6) levels. Despite a clear distinction in pathophysiology, inflammatory reaction may be the major link between these diseases. We hypothesized a relationship between pyridoxal 5'-phosphate (PLP), the active form of vitamin B(6), and the marker of inflammation C-reactive protein (CRP). We also evaluated whether total plasma homocysteine (tHcy), a well-defined risk factor for CVD and a major determinant of plasma PLP levels, had a possible role as a mediator of this hypothesized relationship. METHODS AND RESULTS: Data from 891 participants from the population-based Framingham Heart Study cohort were analyzed. Subjects were divided into 2 groups according to normal or elevated CRP values: group 1, CRP <6 mg/L; group 2, CRP >/=6 mg/L. Plasma PLP levels were substantially lower in group 2 than in group 1 (mean values in group 2, 36.5 nmol/L versus 55.8 nmol/L in group 1, P<0.001). In a multiple logistic regression model adjusted for tHcy, the association of PLP with CRP remained highly significant (P=0.003). CONCLUSIONS: Low plasma PLP is associated with higher CRP levels independently of tHcy. This observation may reflect a vitamin B(6) utilization in the presence of an underlying inflammatory process and represent a possible mechanism to explain the decreased vitamin B(6) levels in CVD.

Renal insufficiency, vitamin B(12) status, and population attributable risk for mild hyperhomocysteinemia among coronary artery disease patients in the era of folic acid-fortified cereal grain flour.

Fortification of enriched cereal grain flour products with folic acid has drastically reduced the prevalence of deficient plasma folate status, a major determinant of plasma total homocysteine (tHcy) levels. We hypothesized that even more liberally defined "suboptimal" plasma folate status might no longer contribute importantly to the population attributable risk (PAR) for mild hyperhomocysteinemia, a putative atherothrombotic risk factor. We determined fasting plasma tHcy, folate, vitamin B(12), and pyridoxal 5'-phosphate levels, along with serum creatinine and albumin levels, in 267 consecutive patients (aged 61+/-9 [mean+/-SD] years, 76.4% men and 26.6% women) with stable coronary artery disease (CAD) who were nonusers of vitamin supplements or had abstained from supplement use for at least 6 weeks before examination. Subjects were evaluated a minimum of 3 months after the implementation of flour fortification was largely completed. Relative risk estimates for the calculation of PAR were derived from a multivariable-adjusted logistic regression model with >/=12 micromol/L tHcy as the dependent variable and with age, sex, pyridoxal 5'-phosphate (continuous), albumin (continuous), <5 ng/mL folate, <250 pg/mL vitamin B(12), and >/=1.3 mg/dL creatinine as the independent variables. The prevalence of >/=12 micromol/L plasma tHcy was 11.2% (30 of 267 patients). PAR estimates (percentage) for >/=12 micromol/L tHcy were as follows: <5 ng/mL folate (<1%), <250 pg/mL vitamin B(12) (24.5%), and >/=1.3 mg/dL creatinine (37.5%). In the era of folic acid-fortified cereal grain flour, renal insufficiency and suboptimal vitamin B(12) status (but not folate status) contribute importantly to the PAR for mild hyperhomocysteinemia among patients with stable CAD.

Nonfasting plasma total homocysteine levels and all-cause and cardiovascular disease mortality in elderly Framingham men and women.

BACKGROUND: Elevated fasting total homocysteine (tHcy) levels were recently shown to confer an independent risk for all-cause and cardiovascular disease (CVD) mortality among selected Norwegian patients with confirmed coronary heart disease. We examined whether elevated fasting plasma tHcy levels were predictive of all-cause and CVD mortality in a large, population-based sample of elderly US women and men. METHODS: Nonfasting plasma tHcy levels were determined in 1933 elderly participants (mean age, 70 +/- 7 years; 58.9% women) from the original Framingham Study cohort, examined between 1979 and 1982, with follow-up through 1992. Unadjusted and adjusted (ie, for age, sex, diabetes, smoking, systolic blood pressure, total and high-density lipoprotein cholesterol, and creatinine) relative risk estimates (with 95% confidence intervals [CIs]) for total and CVD mortality were generated by proportional hazards modeling, with tHcy levels (quartiles) as the independent variable. RESULTS: There were 653 total deaths and 244 CVD deaths during a median follow-up of 10.0 years. Proportional hazards modeling revealed that tHcy levels of 14.26 micromol/L or greater (the upper quartile), vs less than 14.26 micromol/L (the lower three quartiles), were associated with relative risk estimates of 2.18 (95% CI, 1.86-2.56) and 2.17 (95% CI, 1.68-2.82) for all-cause and CVD mortality, respectively. The relative risk estimates after adjustment for age, sex, systolic blood pressure, diabetes, smoking, and total and high-density lipoprotein cholesterol levels attenuated these associations, but they remained significant: 1.54 (95% CI, 1.31-1.82) for all-cause mortality; 1.52 (95% CI, 1.16-1.98) for CVD mortality. CONCLUSION: Elevated nonfasting plasma tHcy levels are independently associated with increased rates of all-cause and CVD mortality in the elderly.

Nutritional factors in physical and cognitive functions of elderly people.

The quality of life of aging individuals depends profoundly on their capacity for physical mobility, mental alertness, and cognitive function. Independence and self-esteem are strongly determined by physical and mental capacities. Stimulated by reports of declining function with age, investigators have examined the relationships between lifestyle factors and maintenance of functional status. Growing evidence supports the view that continued physical activity and good nutritional status are important determinants of physical and cognitive function. It is possible that some of the decline in cognitive function associated with aging is preventable or reversible with improved vitamin nutriture, especially vitamin B-12, vitamin B-6, and folate. It might well be argued that the most practical outcome of research on the relationship of diet and nutrition to the aging process would be a better understanding of the ways in which our behavior can maintain a vigorous quality of life.

Effects of glucose and glucose polymers on calcium absorption in healthy subjects.

Glucose polymers have been shown to enhance intestinal calcium absorption in normal subjects as well as in patients with gastrointestinal disease. Glucose polymers are widely used as an energy source in enteral nutritional supplements and infant formulas. In this study, eight normal subjects underwent 47Ca absorption tests to compare the effect on calcium absorption of carbohydrate given orally as a simple carbohydrate (glucose) or a more complex carbohydrate (glucose polymers). Oral coadministration of glucose with calcium increased the efficiency of intestinal calcium absorption by 20% and coadministration of glucose with glucose polymers increased calcium absorption by 27%. This suggests that glucose, derived from glucose polymers by hydrolysis, may be responsible for the positive effect of polymers on calcium absorption. The potential positive effect of coadministration of carbohydrate on calcium bioavailability deserves considerations in the design of calcium supplementation strategies.

Competitive inhibition of folate absorption by dihydrofolate reductase inhibitors, trimethoprim and pyrimethamine.

Trimethoprim and pyrimethamine, inhibitors of dihydrofolate reductase (DHFR), cause folate deficiency in some patients. We investigated impairment of intestinal folate absorption by these drugs. By use of the in vivo intestinal-loop methods in rats, absorption of [3H] folic acid was significantly decreased in the presence of either drug. Kinetic studies using the influx chamber method demonstrated a pattern of competitive inhibition of folate transport. [3H] folic acid absorption from jejunal loops was determined 3-16 h after IV administration of methotrexate; this treatment abolished DHFR activity in the small intestine. In rats pretreated with methotrexate, luminal disappearance and systemic absorption of folic acid were significantly enhanced with respect to controls. Trimethoprim and pyrimethamine are weak competitive inhibitors of intestinal folate transport and folate absorption inhibition occurs at the site of membrane transport and appears to be unrelated to concurrent inhibition of DHFR activity in enterocytes.

Glucose polymer increases jejunal calcium, magnesium, and zinc absorption in humans.

The present study investigated the effect of glucose polymer on jejunal calcium, magnesium, and zinc absorption in eight normal subjects, using the triple-lumen intestinal perfusion technique. For each subject, a 30-cm segment of jejunum was perfused for 60 min each with two different test solutions. When 4 mM glucose polymer was perfused net calcium absorption increased by fourfold (95 vs 488 mumol/30 cm/h), and net jejunal uptake of magnesium (393 mumol/30 cm/h) was observed, as compared to net magnesium secretion in the absence of glucose polymer. In addition, coadministration of glucose polymer doubled net zinc absorption (13 vs 29 mumol/30 cm/h). The rate of water absorption increased from 49 to 111 ml/30 cm/h. No further change in jejunal water and mineral absorption was observed when glucose polymer in the perfusate was increased from 4 to 8 mM. These results suggest that glucose polymer may have potential as an agent to significantly enhance mineral absorption.

Use of the deoxyuridine suppression test to evaluate localized folate deficiency in rat colonic epithelium.

In this study the deoxyuridine suppression test (dUST) was performed on isolated rat colonocytes to establish its value as an indicator of folate status in the colonic epithelium. [3H]thymidine incorporation into DNA was suppressed greater than 90% by deoxyuridine (dU) concentrations greater than 2.5 mumol/L. Preincubation of cells with 5-fluorouracil (1-100 mumol/L) but not methotrexate (10-100 mumol/L) resulted in a significant decrease in the degree of suppression. The dUST performed on colonocytes from folate-deficient animals displayed less suppression than on colonocytes from folate-replete animals (P less than 0.05). The abnormal degree of suppression was corrected by adding 100 mumol folinic acid/L. There was a negative correlation between the degree of suppression and the folate concentration of the colonic epithelium (P less than 0.001). These data indicate that the dUST is useful for detecting folate deficiency in the colonic epithelium and may therefore be valuable in assessing a deficiency state localized to that epithelium.

Response of fractional calcium absorption in women to various coadministered oral glucose doses.

Previous studies found an enhancing effect of glucose on fractional calcium absorption in humans but little information is available on the effect of different amounts of carbohydrate on Ca absorption. Thus, we studied the response of fractional Ca absorption to various loads of oral glucose coadministration with Ca in ten female subjects. After an overnight fast, 47Ca was administered orally on four occasions in solutions that contained varying doses of glucose (0 control, 56, 222, and 444 mmol). Seven of the ten subjects showed a positive response to glucose. In this group of responders there was a linear response to glucose between 0 and 222 mmol. No further increase was achieved at the higher dose of glucose. The response to 222 mmol glucose represented a 49% increase in Ca absorption compared with absorption without carbohydrate.