Role of intestinal alkaline phosphatase (IAP) in calcium (Ca) absorption

s from the XXVII Annual Meeting of the Argentine Association of Osteology and Mineral Metabolism 9-11th September 2010 Cordoba, Argentina Role of intestinal alkaline phosphatase (IAP) in calcium (Ca) absorption L.R. Brun, L. Arias, M. Alonso, C. Guglielmi, A. Rigalli Bone Biology Laboratory, Rosario, Argentina E-mail address: lbrun@unr.edu.ar The association of IAP with Ca absorption is partially known. Previous experiments indicated that Ca binds to IAP, contributes to maintain the active structure and increases the activity of membrane-bound form. There is evidence that the decrease in pH alters the TRPV6-Ca channel activity. The aim of this study was to evaluate the effect of pH and phosphate generated by the action of the IAP on Ca absorption. Experiments were carried out with everted duodenal sacs. The intestinal mucosa was exposed to a buffer with Ca 1, 10, 50 or 100 mM, pH 9 and the serosa to the same solution without Ca (n=4/group). Phosphorus (P), Ca and pH were measured in the mucosa solution at 0, 10 and 20 min. Ca absorption was calculated by the difference between Ca concentration at 0 and 20 min. The precipitation of Ca phosphate was calculated with pH, P and Ca. Experiments were also carried out in the presence of phenylalanine (Phe), an inhibitor of the IAP. As Ca increased in the solution, there was a significant decrease in Ca absorption (Ca 1: 45±4; Ca 10: 42±11; Ca 50: 38±11; Ca 100: 30±11) and a significant decrease of pH (Ca 1: 7.8±0.1; Ca 10: 7.4± 0.1; Ca 50: 6.9±0.2; Ca 100: 6.9±0.1). Precipitation as Ca phosphate was negligible, and it was not responsible for the decrease in Ca absorption. When the experiments were carried out in the presence of Phe there was an increase in Ca absorption (Ca 1: 53±5; Ca 10: 56± 6; Ca 50: 42±10; Ca 100: 40±6) with a decrease in pH not as evident as in the absence of Phe (Ca 1: 8.33±0.15; Ca 10: 8.05±0.18; Ca 50: 8.17±0.17; Ca 100: 8.28±0.21). These results support the hypothesis that pH regulates the entry of Ca to the enterocyte and acts as a sensor of luminal Ca. This article is part of a Special Issue entitled AAOMM 2010 Abstracts. doi:10.1016/j.bone.2011.03.722 Effect of fluoride on oxygen consumption (OC) by rat tissues B.L. Fina, A. Rigalli Bone Biology Laboratory, Rosario, Argentina E-mail address: arigalli@unr.edu.ar Fluoride (F) enters the body through food, treatments for bone loss or prevention of dental caries. It has a positive effect on bone formation, but it can affect the oxidative stress. Previous reports have been performed usually with F concentrations higher than those found in vivo. The aim of this study was to evaluate the effect of F on OC with F concentrations similar to those in plasma after a dose for osteoporosis treatment or after the consumption of fluoridated water. OC was measured in slices of liver, kidney and muscle with F 0–100 μM. Sprague–Dawley rats were divided into three groups: Control (C), Treated with F (TF): 15 ppm F in drinking water for 30 days (model of caries prevention) and MFP: ovariectomized rats treated with monofluorophosphate 80 μmol/day for 60 days (model of osteoporosis treatment). After euthanasia, slices of tissues were successively exposed to 0, 10, 50 and 100 μM F. The presence of F decreased OC in liver and muscle in all groups. The opposite was observed in kidney. OC consumption is shown as nmol/min·mg protein, mean±SEM. Muscle, 10, 50 μM not shown. *p<0.05 significant difference from 0 μM. Liver: C (0 μM: 15.7±2.5; 100 μM: 10.5±2.2*); TF (0 μM: 14.9±1.5; 100 μM: 9.4±1.1*); MFP (0 μM: 13.1±0.9; 100 μM: 10.2±0.8*). Kidney: C (0 μM: 18.2±1.2; 100 μM: 31.9±2.5*); TF (0 μM: 14.0±1.8; 100 μM: 29.0±5.2*); MFP (0 μM: 18.6±2.0; 100 μM: 32.0±3.0*). Transaminase and creatine kinase activity, creatinine clearance and histological study did not show significant changes in tissues at the beginning of the measurements. Conclusion: F produces changes in OC at concentrations comparable to those found in vivo. These results would indicate that the modification of oxidative stress could be due to changes in the production of reactive oxygen species at the level of the respiratory chain. This article is part of a Special Issue entitled AAOMM 2010 Abstracts. doi:10.1016/j.bone.2011.03.723 Clinical, molecular and bone metabolism studies in patients with Congenital Adrenal Hyperplasia S. Martin, L. Munoz, A. Perez, G. Sobrero, G. Picotto, M. Ochetti, A. Carpentieri, L. Silvano, G. Diaz de Barboza, M. Signorino, C. Ruperez, P. Bertolotto, M.R. Ulla, N. Tolosa de Talamoni, M. Miras Servicio de Endocrinologia Hospital de Ninos, Catedra de Bioquimica y Biologia Molecular FCM-UNC, FAMAF-UNC, CEOM Cordoba, Argentina We investigated final height and clinical and biochemical indicators of the outcome of glucocorticoid therapy in patients with different clinical forms of Congenital Adrenal Hyperplasia (CAH) due to 21-hydroxylase deficiency. The frequencies of polymorphisms of different genes and their associations with parameters of bone metabolism and IGF systems were analyzed. Subjects and methods: In 59 patients with CAH (age 0.5–34 years) 17-OH Progesterone, Androstenedione, DHEA-S, testosterone, osteocalcin, B-crosslaps, IGF1, and IGFBP3 were determined. Using PCR-RFLP methods, vitamin D receptor (Bsm I and Fok I), estrogen receptor (PVU II), type 1 collagen (Bal I), glucocorticoid receptor (Bcl I) gene polymorphisms and IGF1 microsatellites were determined in CAH and 114 normal controls. Final height was analyzed in 43 CAH patients. Results: SDS final height was: male −1.46, female −0.96. The relative frequencies of the polymorphisms analyzed between groups and the healthy controls were similar. No significant associations were found between these genotypes and bone turnover markers, IGF1 or bone mineral density. Conclusions: Our data show that the parameters of bone metabolism and the genotypes analyzed, with a distribution comparable to the normal population, do not yet explain the variation in growth rate and final height. This article is part of a Special Issue entitled AAOMM 2010 Abstracts. doi:10.1016/j.bone.2011.03.724 Modulating effect of monofluorophosphate (MFP) on zoledronate (Z) action in ovariectomized rats (OVX) M. Lombarte, S.M. Roma, H. Moreno, A. Rigalli, V. Di Loreto Bone Biology Laboratory, Rosario, Argentina Several therapies for osteoporosis have been tested combining anabolic and antiresorptive drugs. Z is used as an antiresorptive agent and MFP as bone anabolic agent. The aim of this work was to evaluate histologically the preventive effect of combined use of Z and MFP in OVX rats. Thirty-two female Sprague Dawley rats were subjected to OVX: 1) Controls, 2) MFP: 40 μmol/100 g bw/d per os, 3) Z: 1.5 μg/kg/w sc, and 4) MFP+Z: 40 μmol/100 g bw/