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Acharya M, Singh N, Gupta G, Tambuwala MM, Aljabali AAA, Chellappan DK, Dua K, Goyal R. Vitamin D, Calbindin, and calcium signaling: Unraveling the Alzheimer's connection. Cell Signal 2024; 116:111043. [PMID: 38211841 DOI: 10.1016/j.cellsig.2024.111043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 12/21/2023] [Accepted: 01/08/2024] [Indexed: 01/13/2024]
Abstract
Calcium is a ubiquitous second messenger that is indispensable in regulating neurotransmission and memory formation. A precise intracellular calcium level is achieved through the concerted action of calcium channels, and calcium exerts its effect by binding to an array of calcium-binding proteins, including calmodulin (CAM), calcium-calmodulin complex-dependent protein kinase-II (CAMK-II), calbindin (CAL), and calcineurin (CAN). Calbindin orchestrates a plethora of signaling events that regulate synaptic transmission and depolarizing signals. Vitamin D, an endogenous fat-soluble metabolite, is synthesized in the skin upon exposure to ultraviolet B radiation. It modulates calcium signaling by increasing the expression of the calcium-sensing receptor (CaSR), stimulating phospholipase C activity, and regulating the expression of calcium channels such as TRPV6. Vitamin D also modulates the activity of calcium-binding proteins, including CAM and calbindin, and increases their expression. Calbindin, a high-affinity calcium-binding protein, is involved in calcium buffering and transport in neurons. It has been shown to inhibit apoptosis and caspase-3 activity stimulated by presenilin 1 and 2 in AD. Whereas CAM, another calcium-binding protein, is implicated in regulating neurotransmitter release and memory formation by phosphorylating CAN, CAMK-II, and other calcium-regulated proteins. CAMK-II and CAN regulate actin-induced spine shape changes, which are further modulated by CAM. Low levels of both calbindin and vitamin D are attributed to the pathology of Alzheimer's disease. Further research on vitamin D via calbindin-CAMK-II signaling may provide newer insights, revealing novel therapeutic targets and strategies for treatment.
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Affiliation(s)
- Manish Acharya
- Department of Neuropharmacology, School of Pharmaceutical Sciences, Shoolini University, Himachal Pradesh, India
| | - Nicky Singh
- Department of Neuropharmacology, School of Pharmaceutical Sciences, Shoolini University, Himachal Pradesh, India
| | - Gaurav Gupta
- School of Pharmacy, Suresh Gyan Vihar University, Jagatpura, Jaipur 302017, India
| | - Murtaza M Tambuwala
- Lincoln Medical School, Universities of Nottingham and Lincoln College of Science, Brayford Pool Campus, Lincoln LN6 7TS, UK.
| | - Alaa A A Aljabali
- Faculty of Pharmacy, Department of Pharmaceutical Sciences, Yarmouk University, Irbid 21163, Jordan.
| | - Dinesh Kumar Chellappan
- Department of Life Sciences, School of Pharmacy, International Medical University, Bukit Jalil, Kuala Lumpur 57000, Malaysia.
| | - Kamal Dua
- Discipline of Pharmacy, Graduate School of Health, University of Technology Sydney, Ultimo, NSW 2007, Australia; Faculty of Health, Australian Research Centre in Complementary and Integrative Medicine, University of Technology Sydney, Ultimo, NSW 2007, Australia.
| | - Rohit Goyal
- Department of Neuropharmacology, School of Pharmaceutical Sciences, Shoolini University, Himachal Pradesh, India.
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Bar A. Calcium homeostasis and vitamin D metabolism and expression in strongly calcifying laying birds. Comp Biochem Physiol A Mol Integr Physiol 2008; 151:477-90. [DOI: 10.1016/j.cbpa.2008.07.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 07/03/2008] [Accepted: 07/07/2008] [Indexed: 12/14/2022]
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Bhor VM, Sivakami S. Regional variations in intestinal brush border membrane fluidity and function during diabetes and the role of oxidative stress and non-enzymatic glycation. Mol Cell Biochem 2004; 252:125-32. [PMID: 14577585 DOI: 10.1023/a:1025599126840] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The physical state (fluidity) of lipids modulates the activities of several membrane bound enzymes and transport proteins. Alteration of brush border membrane (BBM) fluidity is one of the several changes exhibited by the small intestine during diabetes. In the present study, an investigation of the diabetes induced regional changes in fluidity, oxidative damage, non-enzymatic glycation as well as the activities and the kinetic parameters of the enzymes alkaline phosphatase and gamma-glutamyl transpeptidase was carried out on the intestinal BBM. At the end of 6 weeks of diabetes, significant increases in the extent of both oxidative damage and non-enzymatic glycation were observed along the length of the intestine along with a simultaneous decrease in membrane fluidity. A significant correlation between the decrease in BBM fluidity and increase in non-enzymatic glycation was observed in the duodenum and jejunum. Additionally regional variations in the activities and kinetic parameters of both the enzymes were observed.
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Affiliation(s)
- V M Bhor
- Department of Life Sciences, University of Mumbai, Santacruz (East), Mumbai 400 098, India
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Haag M, Magada ON, Claassen N, Böhmer LH, Kruger MC. Omega-3 fatty acids modulate ATPases involved in duodenal Ca absorption. Prostaglandins Leukot Essent Fatty Acids 2003; 68:423-9. [PMID: 12798663 DOI: 10.1016/s0952-3278(03)00067-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dietary supplementation with fish oil that contains omega-3 polyunsaturated fatty acids has been shown to enhance bone density as well as duodenal calcium uptake in rats. The latter process is supported by membrane ATPases. The present in vitro study was undertaken to test the effect of omega-3 fatty acids on ATPase activity in isolated basolateral membranes from rat duodenal enterocytes. Ca-ATPase in calmodulin-stripped membranes was activated in a biphasic manner by docosahexanoic acid (DHA) (10-30 microg/ml) but not by eicosapentanoic acid (EPA). This effect was blocked partially by 0.5 microM calphostin (a protein kinase C blocker). DHA inhibited Na,K-ATPase (-49% of basal activity, [DHA]=30 microg/ml, P <0.01). This effect could be reversed partially by 50 microM genistein, a tyrosine kinase blocker. EPA also inhibited Na,K-ATPase: (-47% of basal activity, [EPA]=30 microg/ml, P <0.01), this effect was partially reversed by 100 microM indomethacin, a cyclo-oxygenase blocker. Omega-3 fatty acids are thus involved in multiple signalling effects that effect ATPases in BLM.
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Affiliation(s)
- Marianne Haag
- Department of Physiology, University of Pretoria, PO Box 2034, Pretoria 0001, South Africa.
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Aslamkhan AG, Ahearn GA. Iron uptake by hepatopancreas brush border membrane vesicles (BBMV) of the lobster (Homarus americanus). JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, COMPARATIVE EXPERIMENTAL BIOLOGY 2003; 295:145-50. [PMID: 12541298 DOI: 10.1002/jez.a.10223] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The uptake of (55)Fe(2+) and solubilized (55)Fe(3+) into brush border membrane vesicles prepared from the hepatopancreas of the Atlantic lobster (Homarus americanus) was investigated. Non-specific surface binding of (55)Fe(2+) at equilibrium to the vesicular surface approximated 57% of total (55)Fe(2+) uptake. (55)Fe(2+) uptake showed temperature sensitivity and was trans-stimulated by a Ca(2+) gradient (at 5mM) directed out. Equilibrated (59)Fe(2+) exchanged for both Cd(2+) and cold Fe(2+). The data obtained in this study are suggestive that at least a portion of ferrous iron absorption may occur by a divalent exchanger mechanism.
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Affiliation(s)
- Amy G Aslamkhan
- Department of Physiology, University of Hawaii, Honolulu, Hawaii 96822, USA
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Abstract
Essential fatty acid (EFA)-deficient animals develop severe osteoporosis coupled with increased renal and arterial calcification. This picture is similar to that seen in osteoporosis in the elderly, where the loss of bone calcium is associated with ectopic calcification of other tissues, particularly the arteries and the kidneys. Recent mortality studies indicate that the ectopic calcification may be considerably more dangerous than the osteoporosis itself, since the great majority of excess deaths in women with osteoporosis are vascular and unrelated to fractures or other bone abnormalities. EFAs have now been shown to increase calcium absorption from the gut, in part by enhancing the effects of vitamin D, to reduce urinary excretion of calcium, to increase calcium deposition in bone and improve bone strength and to enhance the synthesis of bone collagen. These desirable actions are associated with reduced ectopic calcification. The interaction between EFA and calcium metabolism deserves further investigation since it may offer novel approaches to osteoporosis and also to the ectopic calcification associated with osteoporosis which seems to be responsible for so many deaths.
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Affiliation(s)
- M C Kruger
- Department of Physiology, University of Pretoria, South Africa
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Tolosa de Talamoni NG. Calcium and phosphorous deficiencies alter the lipid composition and fluidity of intestinal basolateral membranes. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1996; 115:309-15. [PMID: 9008355 DOI: 10.1016/s0300-9629(96)00083-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Steady-state fluorescence polarization and lipid composition studies were undertaken on intestinal basolateral membranes (BLM) from chicks adapted to a calcium deficient (low Ca) or a phosphorous deficient diet (low P). The fluorescence anisotropy showed that fluidity of intestinal BLM was increased by the mineral deprivations, but the response of the membranes varied with the specific fluorophore used. The "static" component of fluidity, assessed by 1,6-diphenyl-1,3,5-hexatriene (DPH), was increased whereas the "dynamic" component, monitored with DL-12-(9-anthroyloxy)-stearic acid (12-AS), was not modified. Low P diet produced significant changes in lipid composition such as a decrease in the cholesterol content and in the sphyngomyelin (Sph) and phosphatidylserine plus phosphatidylinositol fractions (PS + PI) and increment in the phosphatidylcholine (PC) proportion. The percent of monounsaturated fatty acids was increased by the low P diet due mainly to an increase in the oleic acid fraction. Minor changes such as a decrease in the palmitic acid and increases in the 22:5n3 and 22:6n3 fatty acids were caused by Ca deficiency. The alteration of the biochemical and biophysical membrane properties of the BLM of the mineral deficient groups might play a role in the enhanced intestinal Ca and P absorption.
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Abstract
The classical genomic action of steroid hormones acting through intracellular receptors is well recognized. Within this concept of action, questions regarding the ultimate fate of the hormone and lack of a tight correlation between tissue uptake and biological activity with receptor binding remain unanswered. Evidence has accumulated that steroid hormones can exert non-classical action that is characterized by rapid effect of short duration. In most of these cases, the hormone effects occurs at the membrane level and is not associated with entry into the cell. The possible mechanisms for these non-classical actions are: (a) changes in membrane fluidity; (b) steroid hormone acting on receptors on plasma membranes; (c) steroid hormones regulating GABAA receptors on plasma membranes; and (d) activation of steroid receptors by factors such as EGF, IGF-1 and dopamine. Data have also been obtained indicating that receptor-mediated insertion of steroid hormones into DNA may take place with the steroid acting as a transcription factor. These new proposed mechanism of action of steroid hormones should not be viewed as a challenge to the classical mechanism. These diverse modes of action provide for an integrated action of hormones which may be rapid and of short duration or prolonged to address the physiological needs of the individual.
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Affiliation(s)
- D W Brann
- Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000
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Schedl HP, Ronnenberg W, Christensen KK, Hollis BW. Vitamin D and enterocyte brush border membrane calcium transport and fluidity in the rat. Metabolism 1994; 43:1093-103. [PMID: 8084284 DOI: 10.1016/0026-0495(94)90050-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Prior studies of vitamin D repletion showed a threefold increase in the maximum rate (Vmax) for calcium uptake by brush border membrane vesicles, but did not differentiate saturable and nonsaturable uptake components. We studied the calcium uptake and fluidity response of intestinal brush border vesicles to vitamin D by treatment with 1 alpha,25-dihydroxy-24,24-difluorocholecalciferol (24,24-F-1,25-(OH)2D3). Treatment responses were measured by effects on (1) saturable and nonsaturable initial uptake rates of calcium by rat proximal small intestinal brush border membrane vesicles; (2) transmucosal calcium transport by everted duodenal sac; and (3) fluorescence anisotropy. Treatment of vitamin D-depleted weanlings increased the Vmax by 50% (P < .05) in vesicles from the proximal 12 cm of small intestine from rats injected with disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP), but there was no response in rats not injected with EHDP or in vesicles from the proximal 30 cm of small intestine. Vitamin D-depleted weanlings were D-deficient based on serum 25-hydroxycalciferol(25-OH-D) concentration, but to produce 1 alpha,25-dihydroxycalciferol [1,25-(OH)2D] depletion, EHDP injection was required. Treatment of vitamin D-replete adult rats caused a 20% (P < .05) increase in Vmax. Treatment did not affect the calcium concentration at half-Vmax (KT), the rate constant for nonsaturable uptake (KD), or vesicle fluidity measured as fluorescence anisotropy. Contrasting with these minimal effects of treatment on brush border Vmax, treatment increased transmucosal calcium transport by everted duodenal sac almost threefold in vitamin D-depleted weanlings administered EHDP. Thus, vitamin D actions on enterocyte calcium transport (1) at the brush border increase saturable but not nonsaturable uptake, and (2) produce the major transport response distal to the brush border. Despite previously described changes in membrane lipid, brush border fluidity is unaffected by vitamin D treatment.
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Affiliation(s)
- H P Schedl
- Department of Medicine, University of Iowa College of Medicine, Iowa City 52242
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Proulx P. Structure-function relationships in intestinal brush border membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1071:255-71. [PMID: 1958689 DOI: 10.1016/0304-4157(91)90016-p] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- P Proulx
- Department of Biochemistry, Faculty of Medicine, University of Ottawa, Canada
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12
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Schedl HP, Wilson HD, Mathur SN, Murthy S, Field FJ. Effects of phospholipid or cholesterol enrichment of rat intestinal brush border membrane on membrane order and transport of calcium. Metabolism 1989; 38:1164-9. [PMID: 2593830 DOI: 10.1016/0026-0495(89)90153-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Calcium uptake by brush border membrane vesicles from rat small intestine measured under initial rate conditions comprises both saturable and nonsaturable components. Because the brush border is a lipid bilayer and may be sensitive to changes in membrane lipid, vesicles were treated with liposomes to enrich phospholipid (PL) or cholesterol (C) content above that of the control (Reference) vesicle. The effects of the changes in lipid composition on membrane fluidity were determined from fluorescence anisotropy (r) of diphenylhexatriene. Compared with Reference vesicles, liposome-treated vesicles showed decreased Vmax for saturable and KD for nonsaturable uptakes. Liposome treatment changed vesicle phospholipid composition compared with Reference vesicles. Liposome-treated vesicles had similar phospholipid composition but differed in greater cholesterol content of C- compared with PL-vesicles. Mean Vmax and KD were lower in C- than PL-vesicles, but the difference did not reach statistical significance, although fluidity was significantly lower in C- than PL-vesicles. The mechanism of inhibition of saturable calcium uptake in PL- and C-vesicles was uncompetitive. Thus, lipid composition is crucial for determining calcium uptake: any change from native lipid composition decreased transport. Fluidity, measured by the conventional probe diphenylhexatriene, did not correlate with calcium uptake by Reference compared with liposome-treated vesicles.
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Affiliation(s)
- H P Schedl
- Department of Medical Service, Veterans Administration Medical Center, Iowa City, IA
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Rahmani-Jourdheuil D, Juhan-Vague I, Roul C, Mourayre Y, Mishal Z, le Petit J, Vague P. Correction by pentoxifylline of the abnormal fluorescence polarization of erythrocyte membranes from diabetic patients. Eur J Clin Pharmacol 1987; 31:725-8. [PMID: 3556379 DOI: 10.1007/bf00541304] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Erythrocytes from diabetic patients show abnormal rheology. Pentoxifylline, a methylxanthine, improves the abnormal deformability of diabetic erythrocytes, but its mechanism of action remains unclear. We have studied the effect of pentoxifylline on the lipid order of erythrocyte membranes from controls and patients with Type I diabetes. We studied the structural organization of membrane lipids in individual erythrocyte ghosts by fluorescence polarization using a cell sorter. Fluorescence polarization values (P) for 17 controls (P = 0.244) and 20 diabetic patients (P = 0.215) were significantly different. Pentoxifylline added in vitro had no effect on normal membranes, but significantly increased at 10(-5) mol X l-1 (P = 0.233), and normalized at 10(-4) mol X l-1 (P = 0.243), the P value of membrane ghosts from diabetics.
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Abstract
Development of GnRH-mediated gonadotrope desensitization was examined under conditions in which membrane fluidity was altered by temperature and/or chemical means. Cultured pituitary cells were preincubated at temperatures ranging from 4 degrees C to 37 degrees C for 3 h with a desensitizing concentration of GnRH (10(-9) M) or with vehicle alone. Cells were then rinsed and responsiveness assessed by a second 3 h incubation with GnRH at 37 degrees C. As preincubation temperatures decreased from 37 degrees C to 23 degrees C, development of desensitization in gonadotropes was progressively reduced. At 23 degrees C and below, gonadotropes failed to become desensitized to GnRH. Decreases in membrane fluidity occurred over the same temperature range as measured directly by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene incorporated into plasma membrane. When membrane fluidity was increased by incubating cells with the membrane mobilizing agent 2-(2-methoxy-ethoxy)-ethyl-8-(cis-2-n-octylcyclopropyl)-octanoate (A2C), low temperature blockade of GnRH-mediated gonadotrope desensitization was reversed. A2C had no measurable effects on either GnRH receptor binding or number and caused no cytotoxic effects. These studies suggest that development of gonadotropine desensitization to GnRH can be regulated by the state of membrane fluidity.
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Affiliation(s)
- W C Gorospe
- Department of Pharmacology, University of Iowa College of Medicine, Iowa City 52242
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van Os CH. Transcellular calcium transport in intestinal and renal epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 906:195-222. [PMID: 2954588 DOI: 10.1016/0304-4157(87)90012-8] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Ghijsen WE, Ganguli U, Stange G, Gmaj P, Murer H. Calcium uptake into rat small intestinal brush border membrane vesicles: characterization of transmembrane calcium transport at short initial incubation times. Cell Calcium 1987; 8:157-69. [PMID: 2439209 DOI: 10.1016/0143-4160(87)90052-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Calcium transport into brush border vesicles from rat small intestine was investigated by determining uptake rates at very short incubation periods. At incubation times up to 1 second a linear relationship between calcium uptake and time was observed at free calcium concentrations ranging from 1 microM to 5 mM. At time points above 1 second calcium uptake deviates progressively from linearity. Several lines of evidences (EGTA-wash, dependency on membrane potential, temperature sensitivity and effect of the calcium ionophore A23187) suggest transmembrane transport rather than extravesicular binding of calcium as being responsible for calcium uptake. Saturation experiments performed under initial linear and curvilinear uptake conditions show a saturable transport component in the mu molar and only a tendency to saturate in the molar concentration range. It is concluded that uptake values far from equilibrium are characteristic for transmembrane flux of calcium. Transmembrane flux of calcium is mediated by multiple and potential-sensitive mechanisms.
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Pullen GL, Singh SP, Snyder AK, Sethi R, Wahby V. Ethanol influence on calcium uptake and insulin release by rat islets. J Endocrinol Invest 1987; 10:9-14. [PMID: 3110254 DOI: 10.1007/bf03347141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Effect of acute ethanol treatment on simultaneous 45Ca++ uptake and insulin response to glucose was measured in isolated rat pancreatic islets. Ethanol, given ip 1 gm/Kg 1 h prior to sacrifice of the animal, decreased significantly 45Ca++ uptake and insulin response to 8.3 and 16.7 mM glucose. Addition of ethanol to the incubation media inhibited 45Ca++ uptake and insulin release in a dose-related matter. Ionophore A23187, which is known to enhance 45Ca++ efflux, decreased 45Ca++ uptake without affecting insulin release. Inhibitory effects of ethanol and ionophore A23187 were not additive when islets were exposed to both test substances simultaneously. Forskolin, an activator of the adenylate cyclase system potentiated the glucose mediated insulin response in rat islets. However, ethanol decreased the insulin response of islets exposed to glucose and forskolin. The data show that ethanol inhibits 45Ca++ uptake response to glucose and that ethanol influence on insulin release may involve a site beyond the formation of cyclic AMP in the process of excitation-secretion coupling.
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Correction by 1-25-dihydroxycholecalciferol of the abnormal fluidity and lipid composition of enterocyte brush border membranes in vitamin D-deprived rats. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)66580-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Lau K, Langman CB, Gafter U, Dudeja PK, Brasitus TA. Increased calcium absorption in prehypertensive spontaneously hypertensive rat. Role of serum 1,25-dihydroxyvitamin D3 levels and intestinal brush border membrane fluidity. J Clin Invest 1986; 78:1083-90. [PMID: 3760184 PMCID: PMC423766 DOI: 10.1172/jci112664] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Changes in Ca absorption have been described in the spontaneously hypertensive rat (SHR) compared with Wistar-Kyoto (WKy) rats. In 3.5-wk-old SHR and age-matched WKy controls, we measured direct arterial blood pressure, Ca absorption, and serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] levels and small intestine brush border membrane (BBM) fluidity and lipid composition. The two objectives were (a) to define the nature of the absorptive changes before detectable hypertension and (b) to evaluate the potential mechanism(s). We found that even at this normotensive stage (106 +/- 4 vs. 107 +/- 2 torr for the female and 109 +/- 3 vs. 104 +/- 3 torr for the male), the SHR (a) absorbed more Ca (1.46 +/- 0.06 vs. 1.14 +/- 0.08 mmol/d and 1.53 +/- 0.06 vs. 1.28 +/- 0.06 mmol/d, respectively) and retained more Ca, (b) had higher serum 1,25(OH)2D3 levels (340 +/- 36 vs. 160 +/- 18 pg/ml and 230 +/- 25 vs. 150 +/- 16 pg/ml, respectively), and (c) possessed BBM with increased fluidity and with reduced fatty acyl saturation index owing to decreased stearic (32.2 +/- 2.6% vs. 38.2 +/- 0.9%) but increased linoleic acids (12.2 +/- 2.0% vs. 7.6 +/- 1.6%). These results demonstrate increased Ca absorption in prehypertensive SHR associated with increased serum 1,25(OH)2D3 levels, increased intestinal BBM fluidity, and reduced saturation index, which singly or in combination could produce the changes in intestinal Ca transport.
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Abstract
To test the hypothesis that chronic ethanol exposure would alter the membrane fluidity of the intestinal brush-border membrane, which would lead to calcium malabsorption, we gave chicks 15% ethanol in their drinking water from hatching to 3 or 4 wk of age. Although such chicks grew less quickly than their hatchmates not ingesting ethanol, their ability to absorb calcium from the duodenum in vivo was unimpaired. However, when calcium accumulation by isolated duodenal brush-border membrane vesicles (BBMVs) was assessed, the BBMVs from chicks ingesting ethanol for 1-3 wk had a lower rate of uptake than the BBMVs from the controls at all calcium concentrations evaluated (0.1-25 mM). This difference could not be explained by differences in membrane fluidity as assessed by fluorescence depolarization, or by changes in intravesicular volume. Glucose uptake was not affected. The acute addition of ethanol (up to 1 M) in vitro to the control BBMVs increased both membrane fluidity and calcium accumulation. No difference in the fluidizing effect of ethanol in BBMVs between ethanol-ingesting chicks and control chicks could be demonstrated, although the acute effect of ethanol on calcium accumulation was blunted in the BBMVs from chicks ingesting ethanol. Increasing the temperature of the incubation medium also increased membrane fluidity and calcium accumulation in BBMVs from control and ethanol-ingesting chicks, with a greater increase in calcium uptake by the control BBMVs despite comparable increases in fluidity in BBMVs from the control and ethanol-ingesting chicks. We conclude that the chronic ingestion of ethanol by chicks, although markedly altering growth rates, has minimal impact on the intestinal absorption of calcium when assessed in vivo. However, chronic ethanol ingestion does appear to alter the intestinal brush-border membrane to make it less permeable to calcium and less susceptible to the stimulation by ethanol of calcium flux across this membrane; this adaptation may prevent increased flux of calcium across the brush-border membrane into the cell in the presence of ethanol.
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Juhan-Vague I, Rahmani-Jourdheuil D, Mishal Z, Roul C, Mourayre Y, Aillaud MF, Vague P. Correction by insulin added in vitro of abnormal membrane fluidity of the erythrocytes from type 1 (insulin-dependent) diabetic patients. Diabetologia 1986; 29:417-20. [PMID: 3527841 DOI: 10.1007/bf00506531] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Filtrability of erythrocytes obtained from uncontrolled Type 1 (insulin-dependent) diabetic patients is abnormal, but is corrected by insulin added in vivo or in vitro. As erythrocyte filtrability depends on several determinants, we chose to study a membrane property of erythrocytes from diabetic subjects. Membrane fluidity was studied by fluorescence polarization using a lipophilic probe, the diphenyl-hexatriene and the Coulter Epics V together with a laser Spectra-physics 2000. Fluorescence polarization values obtained for 31 normal subjects (0.253 +/- 0.043 SD) and 31 uncontrolled Type 1 diabetic patients (0.231 +/- 0.043 SD) were significantly different (p less than 0.01). Insulin (2.5.10(-9) mol/l) added in vitro increased the fluorescence polarization values of red cell membranes from diabetic patients (without insulin, fluorescence polarization values = 0.210 +/- 0.032 SD; with insulin, fluorescence polarization values = 0.253 +/- 0.024 SD, p less than 0.001, n = 15), but had no effect on normal membranes (without insulin fluorescence polarization values = 0.255 +/- 0.037 SD, with insulin, fluorescence polarization values = 0.251 +/- 0.026 SD; n = 12). Given a relationship between the lipid bilayer and membrane cytoskeleton proteins, this insulin-correctable abnormality of erythrocyte membrane fluidity may be an important determinant of the rheological behaviour of erythrocytes from diabetic patients.
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Merrill AR, Proulx P, Szabo A. Effects of exogenous fatty acids on calcium uptake by brush-border membrane vesicles from rabbit small intestine. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 855:337-44. [PMID: 3081028 DOI: 10.1016/0005-2736(86)90079-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The uptake of a variety of fatty acids by isolated brush-border membranes from rabbit small intestine was studied. This uptake increased with acyl chain-length and was not diminished by washing of the lipid-treated membranes with 0.25 M CsBr. The binding of fatty acid was not accompanied by a decrease in endogenous acyl groups or of cholesterol and therefore corresponded to a net uptake accountable qualitatively and quantitatively by the fatty acid added to the membranes. The uptake of Ca2+ was stimulated by treatment of the membranes with low concentrations of unsaturated fatty acids (0.05 mM) as well as with various concentrations of caprylic acid (0.10-3.00 mM) and inhibited by treatment with higher concentrations of unsaturated fatty acids (0.20-0.60 mM). Saturated fatty acids had no marked effects on Ca2+ uptake. The stimulatory concentrations of unsaturated fatty acids did not change the Ca2+-binding characteristics of the membranes, whereas the higher concentrations decreased equilibrium binding of Ca2+ and very probably the number of high-affinity binding sites. The results of this study are assessed in terms of the effects of normal fatty acids found in the diet on the absorptive properties of the brush-border membranes.
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Hise MK, Weinman EJ. Physical properties of the rat renal brush border membrane during growth. Pflugers Arch 1986; 406:234-6. [PMID: 3008076 DOI: 10.1007/bf00586689] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The biophysical properties of rat renal brush border membranes were examined during neonatal development and following unilateral nephrectomy by sensitive fluorescence techniques. Differences in the fluorescence anisotropy of 1,6 diphenyl-1,3,5-hexatriene (DPH) following unilateral nephrectomy were not apparent; by contrast, the luminal membrane becomes more rigid as animals age. Although growth of the kidneys is common to both states examined, fundamental differences are apparent at the level of the luminal membrane.
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Chan YL, McKay C, Dye E, Slatopolsky E. The effect of 1,25 dihydroxycholecalciferol on parathyroid hormone secretion by monolayer cultures of bovine parathyroid cells. Calcif Tissue Int 1986; 38:27-32. [PMID: 3079648 DOI: 10.1007/bf02556591] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Controversy exists over a direct effect of 1,25(OH)2D3 on PTH secretion. To investigate the possibility that the suppressive effect of 1,25(OH)2D3 on PTH secretion may be demonstrable in 1,25(OH)2D3-depleted tissue and/or after prolonged periods of exposure to 1,25(OH)2D3, primary monolayer cultures of bovine parathyroid cells were established in 1:1 DMEM/Ham's F-12 media supplemented with 2% calf serum but not 1,25(OH)2D3. Ionized calcium was maintained at 1.0 mM. Experiments were performed on 4-day-old culture cells. PTH concentration was measured using both a mid-region/carboxyl and an amino-terminal PTH antisera. 1,25(OH)2D3 at a concentration of 0.1 ng/ml suppressed PTH secretion by 32 +/- 7% after 48 hours. High calcium concentration (2.0 mM) suppressed PTH secretion by 37 +/- 10% and this effect was not additive over that of 1,25(OH)2D3. PTH secretion rate recovered fully 48 hours after normalization of the external calcium concentration but not after the removal of 1,25(OH)2D3. It is concluded that 1,25(OH)2D3 directly suppresses PTH secretion by monolayer culture of bovine parathyroid cells.
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Bikle DD, Munson S. 1,25-Dihydroxyvitamin D increases calmodulin binding to specific proteins in the chick duodenal brush border membrane. J Clin Invest 1985; 76:2312-6. [PMID: 3841129 PMCID: PMC424356 DOI: 10.1172/jci112241] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In previous studies we demonstrated that the biologically active vitamin D metabolite 1,25-dihydroxyvitamin D [1,25(OH)2D] increased the calmodulin (CaM) content of chick duodenal brush border membranes (BBM) without increasing the total cellular CaM content. Therefore, we evaluated the binding of CaM to discrete proteins in the BBM and determined whether 1,25(OH)2D could influence such binding. We observed one major and several minor CaM-binding bands on autoradiograms of sodium dodecyl sulfate polyacrylamide gels incubated with [125I]CaM. The major band had a molecular weight of 102,000-105,000. It bound CaM even in the presence of EGTA, but not in the presence of trifluoperazine or excess nonradioactive CaM. The administration of 1,25(OH)2D increased the apparent binding of CaM to this protein as assessed by densitometry of the autoradiogram. This increase in CaM binding coincided with the increased ability of the same BBM vesicles to accumulate calcium. Cycloheximide in doses that markedly reduced the incorporation of [35S]methionine into BBM proteins did not reduce the ability of 1,25-dihydroxyvitamin D3 to stimulate either calcium uptake by the BBM vesicles or CaM binding to the 102,000-105,000-mol-wt protein. These results suggest that 1,25(OH)2D administration increases the CaM content of duodenal BBM by increasing the ability of a 102,000-105,000-mol-wt protein to bind CaM. This mechanism may underlie the ability of 1,25(OH)2D to stimulate calcium movement across the intestinal BBM.
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Wasserman RH. Vitamin D action. Nutr Rev 1985; 43:127-8. [PMID: 3839060 DOI: 10.1111/j.1753-4887.1985.tb06887.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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Karsenty G, Lacour B, Ulmann A, Piérandréi E, Drüeke T. Phosphate fluxes in isolated enterocytes from vitamin D replete and vitamin D deficient rats--early effects of calcitriol. Pflugers Arch 1985; 403:151-5. [PMID: 3838585 DOI: 10.1007/bf00584093] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In the present work we studied rapid in vitro effects of calcitriol (1,25(OH)2 vitamin D3) on the intestinal transport of inorganic phosphate (Pi). Enterocytes from vitamin D replete (D+) as well as vitamin D depleted (D-) rats were isolated mechanically from the duodeno-jejunum. In this model, Pi uptake was a temperature and Na+-dependent phenomenon. The in vitro-addition of calcitriol (1 pM) resulted in a significant enhancement of initial Pi uptake rate by enterocytes from D+ (P less than 0.01) and D- (P less than 0.05) rats. This effect which was Na+-dependent, was observed within the time of 20 min, but not before. A similar effect on Pi uptake rates of D+ or D- enterocytes could be elicited by the in vitro addition of the methyl ester of cis-vaccinic acid (MCVA) which is thought to increase membrane fluidity by modifying the lipid composition of the cell membrane. The stimulatory effect of calcitriol on Pi uptake rate was blunted in the presence of the methyl ester of transvaccinic acid (MTVA) thought to decrease membrane fluidity. Enterocyte Pi efflux rate constant (oKPi) remained unchanged in the presence of calcitriol (1 pM). In conclusion, the study demonstrates a rapid in vitro effect of calcitriol on Pi uptake by isolated enterocytes from D+ and D- rats. It suggests, but does not prove, that the hormone may act via an action independent of genomic nuclear activation.
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