Improving the energy and nutrient supply for common marmoset monkeys fed under long-term laboratory conditions.

BACKGROUND: Current knowledge about the optimal energy and nutrient supply for common marmoset monkeys (Callithrix jacchus) is scarce, and more information is needed for establishing the underlying nutritional concepts for facilitating longevity of this species as laboratory animals for biomedical research. METHODS: Two feeding experiments were conducted to yield fundamental data about feed acceptance, real feed intake, and feed preferences under laboratory conditions. Newly developed feeding concepts for marmoset monkeys were also examined in preliminary investigations to compare the outcomes with those of a commercial pelletized mixed feed. RESULTS: The first experiments showed preferences for main protein sources in the diets studied, specifically that plant proteins are more accepted than fish meal or egg protein as the main protein source. Several aroma supplements did not modify the acceptance and feed intake markedly. CONCLUSIONS: The newly developed feeding concept yielded promising preliminary data for long-term studies of energy and nutrient supply under laboratory conditions. However, studies of the fundamental requirements are still needed.

Bronchoconstriction in nonhuman primates: a species comparison.

Bronchoconstriction is a characteristic symptom of various chronic obstructive respiratory diseases such as chronic obstructive pulmonary disease and asthma. Precision-cut lung slices (PCLS) are a suitable ex vivo model to study physiological mechanisms of bronchoconstriction in different species. In the present study, we established an ex vivo model of bronchoconstriction in nonhuman primates (NHPs). PCLS prepared from common marmosets, cynomolgus macaques, rhesus macaques, and anubis baboons were stimulated with increasing concentrations of representative bronchoconstrictors: methacholine, histamine, serotonin, leukotriene D4 (LTD4), U46619, and endothelin-1. Alterations in the airway caliber were measured and compared with previously published data from rodents, guinea pigs, and humans. Methacholine induced maximal airway constriction, varying between 74 and 88% in all NHP species, whereas serotonin was ineffective. Histamine induced maximal bronchoconstriction of 77 to 90% in rhesus macaques, cynomolgus macaques, and baboons and a lesser constriction of 53% in marmosets. LTD4 was ineffective in marmosets and rhesus macaques but induced a maximum constriction of 44 to 49% in cynomolgus macaques and baboons. U46619 and endothelin-1 caused airway constriction in all NHP species, with maximum constrictions of 65 to 91% and 70 to 81%, respectively. In conclusion, PCLS from NHPs represent a valuable ex vivo model for studying bronchoconstriction. All NHPs respond to mediators relevant to human airway disorders such as methacholine, histamine, U46619, and endothelin-1 and are insensitive to the rodent mast cell product serotonin. Only PCLS from cynomolgus macaques and baboons, however, responded also to leukotrienes, suggesting that among all compared species, these two NHPs resemble the human airway mechanisms best.

Intrauterine hyperexposure to dexamethasone of the common marmoset monkey revealed normal cerebral metabolite concentrations in adulthood as assessed by quantitative proton magnetic resonance spectroscopy in vivo.

BACKGROUND: Animal models of human brain disorders often have to rely on non-human primates because of their immunological, physiological, and cognitive similarities to humans. METHODS: Localized proton magnetic resonance spectroscopy was performed to assess cerebral metabolite profiles of male common marmoset monkeys in vivo and to determine putative alterations of adult brain metabolism in response to intrauterine hyperexposure to the synthetic glucocorticoid hormone dexamethasone. RESULTS: Excellent spectral quality allowed for absolute quantification of the concentrations of major metabolites in predominantly white matter, gray matter, and thalamus. Marmoset monkeys intrauterinely hyperexposed to dexamethasone revealed normal neurochemical profiles at adulthood. CONCLUSIONS: Prenatally applied dexamethasone does not lead to persistent metabolic alterations affecting adult brain integrity.

A molecular blueprint of gene expression in hippocampal subregions CA1, CA3, and DG is conserved in the brain of the common marmoset.

Recent studies in rodents have shown that there are significant differences in gene expression profiles between the hippocampal subregions CA1, CA3, and DG. These differences in molecular make-up within the hippocampus most likely underlie the differences in morphology, physiology, and vulnerability to insults that exist between the subregions of the hippocampus and are as such part of the basic molecular architecture of the hippocampus. The aim of this study was to investigate at large scale whether these subregional differences in gene expression are conserved in the hippocampus of a nonhuman primate, the common marmoset. This study is very timely, given the recent development of the first marmoset-specific DNA microarray, exclusively containing sequences targeting transcripts derived from the marmoset hippocampus. Hippocampal subregions CA1, CA3, and DG were isolated by laser microdissection and RNA was isolated, amplified, and hybridized to the marmoset-specific microarray (EUMAMA) containing more than 1,500 transcripts expressed in the adult marmoset hippocampus. Large differences in expression were observed in particular between the DG region and both pyramidal subregions. Moreover, the subregion-specific patterns of gene expression showed a remarkable conservation with the rodent brain both in terms of individual genes and degree of differential expression. To our knowledge, this is the first study investigating large scale hippocampal gene expression in a nonhuman primate. The obtained expression profiles not only provide novel data on the expression of more than 1,500 transcripts per hippocampal subregion but also are of potential interest to neuroscientists interested in the role of the different subregions in learning and memory in the nonhuman primate brain.

Prenatal dexamethasone exposure in the common marmoset monkey enhances gene expression of antioxidant enzymes in the aorta of adult offspring.

Human epidemiological studies have indicated that low birth weight associated with an adverse intrauterine environment is related to a greater incidence of cardiovascular disorders in later life. In the foetus, endogenous glucocorticoids generally increase if there is intrauterine nutrient deficiency. The consequent glucocorticoid hyperexposure has been hypothesised to cause in utero programming of atherogenic genes. We investigated the effect of oral treatment with the synthetic glucocorticoid dexamethasone during early or late pregnancy in marmoset monkeys on oxidative and antioxidant status in the offspring. Urinary concentrations of F(2)-isoprostanes were quantified as markers for in vivo oxidative stress. Expression of the mRNAs for the antioxidant enzymes cytosolic glutathione peroxidase (GPx-1), phospholipid hydroperoxide glutathione peroxidase (GPx-4), cytosolic Cu,Zn-superoxide dismutase (SOD1), mitochondrial Mn-superoxide dismutase (SOD2), glutathione reductase (GSR), modifier subunit of glutamate-cysteine ligase (GCLM) and catalase were determined in the aorta. Three groups of pregnant marmosets (10 animals per group) were treated orally for one week with vehicle, or with dexamethasone (5 mg/kg daily) during two gestation windows: early dexamethasone group, pregnancy day 42-48, and late dexamethasone group, pregnancy day 90-96. In one male sibling of each litter (10 males per group), aortas were taken at 2 years of age. In the late dexamethasone group a higher aortic mRNA expression for GPx-1 (p < 0.023), MnSOD (p < 0.016), GCLM (p < 0.019) and GSR (p < 0.014) in comparison to the controls was observed. Aortic expression in the early dexamethasone group was statistically significantly higher only for GSR mRNA (p < 0.038). No significant changes in urinary F(2)-isoprostane concentrations between controls, early and late dexamethasone groups at 2 years of age were observed. Hence, prenatal exposure to dexamethasone in the third trimester leads to increased mRNA expression of several aortic antioxidant enzymes in the offspring. This expression pattern was not temporally related to oxidative stress, and it may reflect in utero re-programming of aortic antioxidant gene expression during prenatal glucocorticoid exposure.

Marmoset CYP3A21, a model for human CYP3A4: protein expression and functional characterization of the promoter.

Due to its small size and the relative evolutionary proximity, the marmoset has been proposed as a model for studies of human drug interactions and metabolism. The current study investigated the expression and regulation of marmoset CYP3A using mass spectrometry and reporter gene techniques. Expression levels of hepatic marmoset CYP3A protein range from 51 to 123 pmol mg-1 total protein (mean 85.2 pmol mg-1, n = 10) and CYP3A21 is the dominant hepatic CYP3A protein in marmosets. The sequence similarity between human CYP3A4 and CYP3A21 across the first 7.5 kb of the cloned CYP3A21 promoter is 88% within the xenobiotic-responsive enhancer module (XREM) and the proximal promoter. Both regulatory modules confer transcriptional activation of CYP3A21-luciferase reporter gene constructs cotransfected with hPXR in intestinal LS174T cells. The pronounced response to rifampin and the moderate response to dexamethasone were similar to those observed with CYP3A4. Taken collectively, these data establish substantial similarities in expression and gene regulation between marmoset CYP3A21 and human CYP3A4. CYP3A21 may be an equivalent of CYP3A4 in New World monkeys, consistent with the phylogenetic relationship between these genes. The marmoset, therefore, appears to be a suitable in vivo model to study CYP3A4 function and regulation.

Hyperketonemia impairs glucose metabolism in pregnant and nonpregnant ewes.

The present study was undertaken to test the hypothesis that high ketone body concentrations suppress endogenous production of glucose and in pregnant sheep facilitate development of pregnancy toxemia. Rates of endogenous glucose production [mmol.min(-1)], and rate constants of glucose turnover [min(-1)] were measured in seven 12-h fasted sheep in the presence of normo- and hyperketonemia by use of D-2-[(3)H]-glucose. The measurements were carried out in the same sheep during the nonpregnant nonlactating state, during late pregnancy (10 +/- 7 d antepartum) and during lactation (19 +/- 6 d postpartum). Hyperketonemia (5 to 7 mmol.L(-1)), similar to that present in spontaneous ovine pregnancy toxemia, was induced by continuous intravenous 4-h infusions of DL-beta-hydroxybutyrate (DL-BHB). Glucose turnover [mmol.min(-1)] in the same 7 nonpregnant nonlactating, late pregnant, and lactating sheep was significantly greater during normoketonemia (0.80, 1.16, 1.76) than during hyperketonemia (0.66, 0.92, 1.16, respectively). The rate constants of glucose turnover were not altered by elevation of the BHB concentration. The results demonstrated that high BHB concentrations significantly suppressed endogenous glucose production but showed no effect on glucose utilization. The suppressive effect of hyperketonemia on hepatic glucose production resulted in a significant reduction of plasma glucose concentration and was qualitatively the same in all three reproductive states. The results indicate that hyperketonemia, which is regularly present in late twin pregnant hypoglycemic sheep contributes significantly to the reduction of available glucose. This effect of hyperketonemia may invoke sustained hypoglycemia and may render the ewe into a vicious cycle that probably makes the animal refractory to treatment in most cases.

Hypocalcemia reduces endogenous glucose production in hyperketonemic sheep.

In previous experiments it has been shown that hyperketonemia lowered plasma glucose concentration in sheep and depressed endogenous glucose production by approximately 30%. This facilitates the onset of pregnancy toxemia. In the last trimester of gestation, hyperketonemia in sheep is often associated with hypocalcemia. There is an indication that hypocalcemia exerts an additional depressive effect on endogenous glucose production. The present study was undertaken to examine the effect in sheep of hypocalcemia on endogenous glucose production in the presence of normo- and hyperketonemia. The experiments were carried out with seven multiparous sheep during three different reproductive states, i.e., during pregnancy (10 +/- 8 d prepartum), during lactation (21 +/- 8 d postpartum), and 4 wk after weaning of the lambs. Concentration of glucose in plasma, turnover of glucose and the rate constant of glucose turnover were measured by isotope dilution during normo- and hypocalcemia and in the presence of normal and elevated beta-hydroxybutyrate (BHB) concentrations. Hypocalcemia was induced by i.v. infusions of Na2EDTA. Hyperketonemia was maintained by i.v. infusion of DL-beta-hydroxybutyrate. The experiments showed that induction of hypocalcemia: 1) induced a decline in plasma glucose concentration in all reproductive states during normo- and hyperketonemia and 2) significantly lowered endogenous production of glucose in nonpregnant hyperketonemic and in lactating normoketonemic ewes. Pregnant normoketonemic ewes were able to compensate for the hypoglycemic effect of hypocalcemia and to keep endogenous production at the normocalcemic level. We concluded that hypocalcemia does not promote the onset of pregnancy toxemia per se but will facilitate the development of the disease when it is present in combination with hyperketonemia.

Hypocalcemia reduces insulin turnover but not insulin-mediated glucose metabolism in piglets.

Disturbances of glucose metabolism similar to type II diabetes are often accompanied by low extra cellular calcium concentrations, as shown in periparturient ruminants. Hypocalcemia reduces insulin secretion and possibly endogenous glucose production, but whether hypocalcemia also affects peripheral actions of insulin is not clear. The problem was investigated with piglets in this study. Insulin-mediated turnover of glucose and the clearance of insulin were measured in 7 control piglets (+D) and in 10 piglets with inherited calcitriol deficiency (-D). The measurements involved continuous intravenous infusions of insulin (1, 2, 5, 7.5 and 10 mU x kg(-1) x min(-1)) and glucose to maintain a glucose concentration of 7 mmol x l(-1) (combined insulin and glucose clamps). Both groups of piglets were studied under normo- and hypocalcemic conditions. During hypocalcemia and with equal insulin infusion rates, -D and +D piglets attained significantly higher (28%-133%) steady state insulin concentrations in plasma than during normocalcemia. This showed that the clearance rates of insulin during hypocalcemia were 48% lower in +D and 20% lower in -D piglets than during normocalcemia. With equivalent insulin infusion rates +D piglets developed significantly higher (15%-48%) steady state insulin concentrations in plasma than -D piglets, indicating that the clearance rate of insulin was higher in the calcitriol-deficient state. The relationship between insulin concentration in plasma and glucose turnover (measured with [3-(3)H]glucose) was not influenced by the calcemic and vitamin D status of the piglets. This indicated that the peripheral action of insulin on glucose metabolism was not influenced by the extracellular calcium concentration and vitamin D status.

Effect of hypocalcaemia on glucose metabolism in hyperketonaemic piglets.

In nine 2- to 3-month-old hyperketonaemic piglets the kinetics of glucose and D-beta-hydroxybutyrate (D-BHB) metabolism were studied during hypo- and normocalcaemia in paired experiments. Hyperketonaemia (1.3 and 2.5 mmol D-BHB (l plasma)-1) was generated by a stepwise increase of DL-BHB infusion. Hypocalcaemia spontaneously developed in five piglets due to an inherited calcitriol deficiency and was induced in four control piglets by a continuous infusion of Na2-EDTA. The method of single isotopic marker injections of glucose and D-BHB was used to calculate replacement rates, rate constants and half-lives of glucose and D-BHB in plasma. When DL-BHB was infused at the same rate into normo- and hypocalcaemic piglets, hypocalcaemia reduced the rate constant of glucose by 20-30% and the replacement rate of glucose by 34%. In the presence of hyperketonaemia, hypocalcaemia increased the rate of replacement of D-BHB by 6-40%. The replacement rate represents the sum of endogenous production and the rate of DL-BHB infusion. This observation shows that the endogenous production of D-BHB was higher during hypocalcaemia than during normocalcaemia.

Peculiarities of vitamin D and of the calcium and phosphate homeostatic system in horses.

The aim of the present study was to investigate the importance of putative regulatory factors of the calcium (Ca) and inorganic phosphate (P(i)) homeostatic system in the horse. The concentrations of Ca, P(i), vitamin D metabolites, parathyroid hormone (PTH), the activity of the alkaline phosphatase (AP) and the concentration and binding properties of vitamin D binding protein (DBP) were measured in the plasma. In addition, the ability of the renal cortex to hydroxylate calcidiol into 24,25(OH)2D3 and 1,25(OH)2D3 was evaluated in vitro. The plasma concentration of Ca (3.2 +/- 0.15 mmol.L-1, N = 100) showed no significant differences between different horse breeds and was not influenced by Ca intake, exercise or by indoor maintenance. The concentration of plasma P(i) which ranged from 0.58 to 1.99 mmol.L-1 was negatively correlated with age and positively correlated with the P content of the feed. AP activities in plasma ranging from 131 to 852 U.L-1 were also negatively correlated with age tended to be higher in horses than in other domestic animals. Plasma concentrations of calcidiol and 24,25(OH)2D were much lower than in most other mammals and birds. The concentration and binding properties of DBP to calcidiol were not markedly different from those of other mammals. The mean plasma concentration of calcitriol (55 +/- 24 pmol.L-1, N = 19) was much lower than in other mammals. The plasma concentration of PTH was 218 +/- 181 ng.L-1. In renal cortex homogenates, only 25-hydroxycholecalciferol-24-hydroxylase activity could be detected (Vmax: 0.42 +/- 0.11 pmol.min-1.mg-1 protein; Km: 373 +/- 263 nmol.L-1). In conclusion, this study provided evidence that in contrast to other species, vitamin D does not appear to play a key role in regulating Ca and P(i) homeostasis in horses.

[Effect of insulin on glucose and and fat metabolism in ewes during various reproductive states in normal and hypocalcemia]. / Insulinwirkung auf Glucose- und Fettstoffwechsel beim Schaf während verschiedener Reproduktionsstadien bei Normo- und Hypocalcämie.

Metabolic indicators of glucose and lipid metabolism, i.e. glucose turnover, insulin concentration in plasma, insulin clearance, concentrations of non-esterified fatty acids (NEFA), glycerol and potassium were investigated in nine ewes during three reproductive states in order to examine their importance for development of subclinical ketosis. The increase of insulin in plasma was measured after a continuous 60 min intravenous infusion of glucose (4.9 mmol.min-1). Turnover of glucose and insulin clearance were quantified during a combined euglycemic, hyperinsulinemic clamp. Insulin was consecutively infused in doses of 5 and 10 mU.kg-1.min-1 for about 2 1/2 hours, each. Plasma glucose concentration was adjusted to 5.3 to 5.8 mmol.l-1. The experiments were carried out during non-pregnancy and non-lactation, 4 weeks to 3 days before lambing and 3 to 4 weeks after lambing, each during normo- and hypocalcemia. Hypocalcemia (0.9 to 1.0 mmol Ca2+.l-1) was induced by continuous i.v. infusion of a 5% Na-EDTA solution. Infusion rate was continuously adjusted. The glucose induced increase in plasma insulin concentration was significantly lower during late pregnancy compared to peak lactation and non-pregnancy (46.3, 62.4 and 128 mU.l-1, respectively). The insulin clearance during a hyperinsulinemic clamp with 5 mU.kg-1.min-1 was significantly less during late pregnancy compared to peak lactation and non-pregnancy (3.7, 6.0, 4.8 ml.kg-1.min-1, respectively). The concentrations of NEFA and glycerol in plasma during the infusion of 5 mU insulin.kg-1.min-1 were significantly higher during late pregnancy than during non-pregnancy (NEFA: 0.41, 0.04 mmol.l-1; glycerol: 96, 29 mumol.l-1, respectively). The results showed that insulin responsiveness was significantly reduced in sheep during late pregnancy. The insulin-mediated uptake of glucose by muscle and fat tissues and the insulin-mediated inhibition of lipolysis were significantly reduced during late pregnancy compared to non-pregnancy and lactation. The diminished responsiveness of target tissue towards insulin during late pregnancy predisposed the animals for development of subclinical ketosis. Hypocalcemia exaggerated this situation by its inhibitory effect on hepatic gluconeogenesis and by enhancing insulin resistance of target tissues. The factors which are responsible for the altered responsiveness of target tissues towards insulin during late pregnancy are yet unknown. The potassium concentration in plasma showed a proportional increase with increase of the energy deficit of the target tissues. This effect could have been exerted by a decrease in cellular concentration of ATP and a concomitant reduction of the activity of Na(+)-K(+)-ATPase. The indicators of glucose and lipid metabolism which were examined in this study showed marked individual variation, particularly during late pregnancy. The marked changes of these indicators with reproductive stages as well as their great variation between individual sheep support the assumption that they are of significance for the development of pregnancy toxemia in sheep.

Role of calbindin-D9k in buffering cytosolic free Ca2+ ions in pig duodenal enterocytes.

1. The aim of the present study was to test whether the vitamin D-dependent Ca(2+)-binding protein calbindin-D9k could function as an important cytosolic Ca2+ buffer in duodenal enterocytes while facilitating transepithelial active transport of Ca2+ ions. For the investigations we used dual-wavelength, fluorescence ratio imaging, with fura-2 as the Ca(2+)-sensitive dye, to measure changes in cytosolic concentrations of free Ca2+ ions ([Ca2+]i) in isolated pig duodenal enterocytes affected by different cytosolic calbindin-D9k concentrations. 2. Epithelial cells were obtained from weaned piglets with normal calbindin-D9k concentrations (con-piglets), from piglets with low calbindin-D9k levels due to inherited calcitriol deficiency caused by defective renal 25-hydroxycholecalciferol D3-1 alpha-hydroxylase activity (def-piglets), and from piglets with reconstituted calbindin-D9k concentrations, i.e. def-animals treated with high doses of vitamin D3 which elevated plasma calcitriol levels by extrarenal production (def-D3-piglets). Basal levels of [Ca2+]i ranged between 170 and 205 nM and did not differ significantly between the groups. 3. After addition of 5 mM theophylline, the [Ca2+]i in enterocytes from con-piglets doubled during the 10 min incubation. This effect, however, was three times higher in enterocytes from def-piglets compared with those from con-piglets. Similar results were obtained after 4 min incubation of enterocytes from con- and def-piglets in the presence of 1 microM ionomycin. In preparations from def-D3-piglets, ionomycin-induced increases in [Ca2+]i were significantly lower compared with enterocytes from def-piglets and were not different from the control values. 4. From the results, substantial support is given for the hypothesis that one of the major functions of mucosal calbindin-D9k is the effective buffering of Ca2+ ions.

Evidence for vitamin D-independent active calcium absorption in newborn piglets.

The role of 1,25-dihydroxycholecalciferol (calcitriol) for intestinal calcium (Ca2+) absorption was studied in newborn (< 1 week old) and weaned piglets (> 6 weeks old). In both groups, normal piglets and piglets suffering from inherited pseudo vitamin D-deficiency rickets, type I (PVDRI) were used. In this inherited disorder, renal production of calcitriol is absent. Plasma samples were assayed for calcitriol and total Ca, and dissociation constants (Kd) and maximum binding capacities (Bmax) of intestinal calcitriol receptors were determined under equilibrium conditions at 4 degrees C. Unidirectional Ca(2+)-flux rates were measured across stripped duodenal mucosae in Ussing chambers in the absence of electrochemical gradients. The plasma calcitriol concentrations of neonatal (26.5 +/- 7.1 pg/ml, n = 11; mean +/- SEM) and weaned PVDRI piglets (18.8 +/- 5.7 pg/ml, n = 8) were unphysiologically low and differed significantly from control animals (83.6 +/- 14.8 pg/ml, n = 8, and 86.9 +/- 9.6 pg/ml, n = 11, respectively). However, newborn PVDRI piglets had normal plasma Ca levels at least during the first days of life. They became hypocalcemic and developed clinical symptoms of rickets during the following weeks. In newborn PVDRI and control piglets, Bmax was significantly lower (84 +/- 28 fmol/mg protein and 127 +/- 55 fmol/mg protein, n = 9, respectively) than in weaned piglets (741 +/- 82 fmol/mg protein, n = 9, and 778 +/- 121 fmol/mg protein, n = 8, respectively). Significant net Ca(2+)-fluxes were found in both newborn PVDRI and control piglets (88.8 +/- 25.1 nmol.cm-2 x h-1, n = 6, and 86.5 +/- 10.5 nmol.cm-2 x h-1, n = 9, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of hypocalcemia/hypophosphatemia on porcine bone and dental hard tissues in an inherited form of type 1 pseudo-vitamin D deficiency rickets.

The effects of Vitamin D deficiency rickets on the formation of mineralized dental tissues were studied in a breed of pigs which had moderate and marked hypocalcemia because of an inherited defect in the renal production of the biologically-active Vitamin D metabolites. Affected piglets developed classical symptoms of rickets which were fatal unless Vitamin D supplements were given. The dissected mandibles of homozygous (rickets) and heterozygous (normal) pigs were photographed and radiographed. Compared with those of normal pigs, the mandibles of homozygous pigs demonstrated slowed development/eruption of permanent teeth, under-mineralized bone, underdeveloped dentin (enlarged pulp chambers), interglobular dentin, and enamel hypoplasia. Enamel defects in rachitic pig teeth were difficult to observe radiographically, but could be detected visually and by SDS-PAGE analysis of the enamel protein components of developing and maturing enamel. There was significant retention of amelogenins in the enamel maturation zones of developing molars taken from rachitic pigs, but there was no obvious difference in the patterns of amelogenin processing.

Hypocalcemia reduces rate of disappearance of glucose from plasma.

The influence of hypocalcemia on glucose disposal from plasma was studied in 4.5 to 24 kg weaned, fasted, calcitriol deficient piglets, which suffered from type I inherited pseudo vitamin D deficiency rickets. The plasma glucose concentration of the piglets was clamped to 40% above its preinfusional level by a continuous intravenous infusion of glucose. This suppressed hepatic glucose production. Since the clamped plasma glucose concentration was below its renal threshold, the rate of steady state glucose infusion served as an estimate for glucose disposal from plasma. It was found that hypocalcemia, generated either by calcitriol deficiency or by continuous EDTA infusions, reduced glucose disposal from plasma by 56-76% compared to normocalcemic control piglets. It was suggested that the effect was not compounded by plasma phosphate, calcitriol or insulin. It was further suggested that hypocalcemia depressed the rate of glucose utilization.