Net calcium efflux from live bone during chronic metabolic, but not respiratory, acidosis

1989 ◽  
Vol 256 (5) ◽  
pp. F836-F842 ◽  
Author(s):  
D. A. Bushinsky
Keyword(s):  
Metabolic Acidosis ◽  
Bone Cells ◽  
Respiratory Acidosis ◽  
Neonatal Mouse ◽  
Mineral Dissolution ◽  
Calcium Flux ◽  
Calcium Efflux ◽  
Physicochemical Factors ◽  
Acute Metabolic Acidosis

In vivo chronic metabolic acidosis induces bone mineral dissolution. Whether the dissolution is due to alterations in physicochemical factors alone, as in acute metabolic acidosis, or requires participation of bone cells is not clear. The effect of chronic respiratory acidosis on bone has also not been established. To determine the effects of chronic metabolic and respiratory acidosis on net calcium flux from bone, we cultured live and dead neonatal mouse calvariae for 99 h in control medium or in medium acidified (pH approximately equal to 7.1) either by lowering the bicarbonate concentration (Met) or by increasing the PCO2 (Resp). We measured net calcium flux (JCa) over 0-48, 48-96, and 96-99 h. Over the first 48 h, there was greater net calcium efflux from live and dead Met than from both Resp groups. All four acidic groups had greater net calcium efflux than controls. Over the last 51 h of the chronic 99 h culture, there was net calcium efflux only from live Met (JCa = 285 +/- 129 nmol.bone-1.3 h-1) and not from any of the other groups (live control, JCa = -183 +/- 24; live Resp, JCa = -110 +/- 22; dead control, JCa = -256 +/- 12; dead Met, JCa = 11 +/- 78; dead Resp, JCa = -27 +/- 47; each P less than 0.02 vs. live Met). There is net calcium efflux from live cultured neonatal mouse calvariae during chronic metabolic, but not respiratory, acidosis. During chronic acidosis, decreased medium bicarbonate, and not just a fall in pH, is necessary to enhance net calcium efflux from live bone.

Net proton influx into bone during metabolic, but not respiratory, acidosis

1988 ◽  
Vol 254 (3) ◽  
pp. F306-F310 ◽  
Author(s):  
D. A. Bushinsky
Keyword(s):  
Metabolic Acidosis ◽  
Bone Mineral ◽  
Respiratory Acidosis ◽  
Mineral Dissolution ◽  
Calcium Efflux ◽  
Bicarbonate Concentration ◽  
Medium Ph ◽  
Acute Metabolic Acidosis ◽  
Initial Medium

During acute metabolic acidosis there is a net influx of protons into bone, decreasing the elevated proton concentration. Whether there is an influx of protons into bone during acute respiratory acidosis is not known. To determine the effect of respiratory acidosis on net proton flux (JH) relative to bone, we compared JH from neonatal mouse calvariae incubated for 3 h in medium acidified by an increase in PCO2 (respiratory acidosis) with that from calvariae incubated in medium acidified to the same extent by a decrease in bicarbonate concentration (metabolic acidosis). The initial medium pH with respiratory acidosis was not different from that with metabolic acidosis (7.108 +/- 0.005 vs. 7.091 +/- 0.007, respectively, P = NS). During respiratory acidosis there was no JH from bone relative to the medium (JH = 236 +/- 93 neq.bone-1.3h-1, P = NS vs. 0); however, during metabolic acidosis there was net proton influx from the medium into bone (JH = -703 +/- 108, P less than 0.05 vs. 0, P less than 0.001 vs. respiratory acidosis). There was less calcium efflux from bone during respiratory than during metabolic acidosis (JCa = 68 +/- 6 nmol.bone-1.3 h-1 vs. 100 +/- 9, respectively, P less than 0.001). There is a net influx of protons into bone in vitro during acute metabolic, but not during acute respiratory, acidosis. The smaller calcium efflux during respiratory acidosis may indicate less net bone mineral dissolution and thus less buffer release into the medium.

In vitro metabolic and respiratory acidosis selectively inhibit osteoblastic matrix gene expression

1999 ◽  
Vol 277 (5) ◽  
pp. F750-F755 ◽  
Author(s):  
Kevin K. Frick ◽  
David A. Bushinsky
Keyword(s):  
Metabolic Acidosis ◽  
Collagen Synthesis ◽  
Bone Cells ◽  
Respiratory Acidosis ◽  
Bone Cell ◽  
Matrix Gla Protein ◽  
Calcium Excretion ◽  
Calcium Efflux ◽  
Matrix Gene ◽  
Significant Difference

Clinically, a decrease in blood pH may be due to either a reduction in bicarbonate concentration ([H[Formula: see text]], metabolic acidosis) or an increase in[Formula: see text] (respiratory acidosis). In mammals, metabolic acidosis induces a far greater increase in urine calcium excretion than respiratory acidosis. In cultured bone, metabolic acidosis induces a marked increase in calcium efflux and a decrease in osteoblastic collagen synthesis, whereas isohydric respiratory acidosis has little effect on either parameter. We have shown that metabolic acidosis prevents the normal developmental increase in the expression of RNA for matrix Gla protein and osteopontin in chronic cultures of primary murine calvarial bone cells (predominantly osteoblasts) but does not alter expression of osteonectin. To compare the effects of isohydric metabolic and respiratory acidosis on expression of these genes, bone cell cultures were incubated in medium at pH ∼7.2 to model metabolic ([H[Formula: see text]], ∼13 mM) or respiratory ([Formula: see text], ∼80 mmHg) acidosis or at pH ∼7.4 as a control. Cells were sampled at weeks 4, 5, and 6 to assess specific RNA content. At all time periods studied, both metabolic and respiratory acidosis inhibited the expression of RNA for matrix Gla protein and osteopontin to a similar extent, whereas there was no change in osteonectin expression. In contrast to the significant difference in the effects of metabolic and respiratory acidosis on bone calcium efflux and osteoblastic collagen synthesis, these two forms of acidosis have a similar effect on osteoblastic RNA expression of both matrix Gla protein and osteopontin. Thus, although several aspects of bone cell function are dependent on the type of acidosis, expression of these two matrix genes appears to be regulated by extracellular pH, independently of the type of acidosis.

Greater unidirectional calcium efflux from bone during metabolic, compared with respiratory, acidosis

1992 ◽  
Vol 262 (3) ◽  
pp. F425-F431 ◽  
Author(s):  
D. A. Bushinsky ◽  
N. E. Sessler ◽  
N. S. Krieger
Keyword(s):  
Driving Force ◽  
Respiratory Acidosis ◽  
Mineral Dissolution ◽  
Calcium Flux ◽  
Calcium Efflux ◽  
Carbonated Apatite ◽  
Acid Base Status ◽  
45Ca Efflux ◽  
45Ca Release

There is a smaller net calcium efflux from bone in vitro during respiratory (increased PCO2) than metabolic (decreased [HCO3-] acidosis. This could be due to the elevated PCO2, which would lessen the driving force for mineral dissolution and increase the driving force for mineralization with respect to carbonated apatite in the bone mineral. To test this hypothesis, we injected neonatal mice with 45Ca and dissected the radiolabeled calvariae 24 h later. The live calvariae were then cultured for 24 h under conditions simulating respiratory acidosis (Resp, pH = 7.225 +/- 0.003, PCO2 = 87.5 +/- 0.1 mmHg), severe respiratory acidosis (SResp, pH = 7.072 +/- 0.004, PCO2 = 103.0 +/- 0.5 mmHg), metabolic acidosis (Met, pH = 7.212 +/- 0.003, HCO3- = 15.5 +/- 0.1 meq/l), or normal acid-base status (Ctl, pH = 7.452 +/- 0.003, PCO2 = 40.0 +/- 0.2 mmHg, HCO3- = 27.8 +/- 0.2 meq/l) and bidirectional net calcium flux (JCa) and unidirectional 45Ca release were determined. There was greater JCa from bone during Met than Resp, and JCa was not different from Met during SResp despite the latter having a significantly lower pH. There was greater unidirectional 45Ca release from bone during Met than Resp, SResp, or Ctl. There was a similar direct correlation between JCa and 45Ca efflux in the respiratory and metabolic groups. However, when calvarial osteoclast activity was inhibited with calcitonin,although there was again greater JCa and 45Ca release with a metabolic compared with respiratory acidosis, there was a greater proportion of 45Ca release than JCa from bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of liver intracellular pH in vivo and its homeostasis in acute acidosis and alkalosis

1979 ◽  
Vol 236 (3) ◽  
pp. F240-F245 ◽  
Author(s):  
R. Park ◽  
W. J. Leach ◽  
A. I. Arieff
Keyword(s):  
Metabolic Acidosis ◽  
Intracellular Ph ◽  
Venous Blood ◽  
Respiratory Acidosis ◽  
Normal Liver ◽  
Respiratory Alkalosis ◽  
Arterial Blood ◽  
Acute Metabolic Acidosis

An in vivo method is presented for the determination of liver intracellular pH (pHi) using [14C]dimethadione (DMO) in dogs. This method differs from those previously published in that hepatic venous and portal venous blood pH were selected as the extracellular reference pH, and liver blood space corrections are applied to whole liver tissue [14C]DMO activity. Using these corrections, a normal liver pHi of 6.99 +/- 0.03 (SE) was obtained. During acute metabolic acidosis and alkalosis, as well as during acute respiratory acidosis and alkalosis, the liver pHi remained normal; metabolic acidosis was 7.04 +/- 0.04; metabolic alkalosis was 6.92 +/- 0.08; respiratory acidosis was 6.98 +/- 0.04; and respiratory alkalosis was 7.00 +/- 0.10. None of these values was significantly different from normal (P greater than 0.05). Changes in intracellular bicarbonate and lactate appeared to account in part for the observed stability of the liver pHi despite acute manipulations resulting in a range of pH values between 7.09 and 7.63 in arterial blood.

scholarly journals Effect of metabolic and respiratory acidosis on intracellular calcium in osteoblasts

2010 ◽  
Vol 299 (2) ◽  
pp. F418-F425 ◽  
Author(s):  
Kevin K. Frick ◽  
David A. Bushinsky
Keyword(s):  
Metabolic Acidosis ◽  
Cho Cells ◽  
Bone Cells ◽  
Primary Cultures ◽  
Chinese Hamster ◽  
Respiratory Acidosis ◽  
Transient Increase ◽  
Intracellular Ca ◽  
Primary Bone

In vivo, metabolic acidosis {decreased pH from decreased bicarbonate concentration ([HCO3−])} increases urine calcium (Ca) without increased intestinal Ca absorption, resulting in a loss of bone Ca. Conversely, respiratory acidosis [decreased pH from increased partial pressure of carbon dioxide (Pco2)] does not appreciably alter Ca homeostasis. In cultured bone, chronic metabolic acidosis (Met) significantly increases cell-mediated net Ca efflux while isohydric respiratory acidosis (Resp) does not. The proton receptor, OGR1, appears critical for cell-mediated, metabolic acid-induced bone resorption. Perfusion of primary bone cells or OGR1-transfected Chinese hamster ovary (CHO) cells with Met induces transient peaks of intracellular Ca (Cai). To determine whether Resp increases Cai, as does Met, we imaged Cai in primary cultures of bone cells. pH for Met = 7.07 ([HCO3−] = 11.8 mM) and for Resp = 7.13 (Pco2 = 88.4 mmHg) were similar and lower than neutral (7.41). Both Met and Resp induced a marked, transient increase in Cai in individual bone cells; however, Met stimulated Cai to a greater extent than Resp. We used OGR1-transfected CHO cells to determine whether OGR1 was responsible for the greater increase in Cai in Met than Resp. Both Met and Resp induced a marked, transient increase in Cai in OGR1-transfected CHO cells; however, in these cells Met was not different than Resp. Thus, the greater induction of Cai by Met in primary bone cells is not a function of OGR1 alone, but must involve H+ receptors other than OGR1, or pathways sensitive to Pco2, HCO3−, or total CO2 that modify the effect of H+ in primary bone cells.

Mechanism of aluminum-induced calcium efflux from cultured neonatal mouse calvariae

1990 ◽  
Vol 258 (3) ◽  
pp. F583-F588 ◽  
Author(s):  
S. M. Sprague ◽  
D. A. Bushinsky
Keyword(s):  
Bone Mineral ◽  
Calcium Influx ◽  
Neonatal Mouse ◽  
Mineral Dissolution ◽  
Calcium Flux ◽  
Calcium Efflux ◽  
Dead Bone ◽  
45Ca Efflux ◽  
Dose Dependent

Aluminum has been shown to increase unidirectional 45Ca efflux from prelabeled bones in vitro; whether aluminum affects net calcium efflux and, if so, by what mechanism has not been studied. To examine the effects of aluminum on net calcium flux from bone we cultured live and dead neonatal mouse calvariae with and without graded concentrations of aluminum (10(-8) to 10(-5) M). Aluminum induced a dose-dependent net calcium efflux from live bone after 24 h, but not 3 h, which was similar in magnitude to that produced by 10(-8) M parathyroid hormone. The normal calcium influx into dead bone was not altered by aluminum. Release of beta-glucuronidase, a lysosomal enzyme released by osteoclasts, increased after a 24-h incubation in aluminum-containing medium and was correlated with net calcium efflux. Calcitonin, an inhibitor of osteoclastic bone mineral dissolution, abolished the increase in beta-glucuronidase release and nullified the aluminum-induced net calcium efflux. Thus aluminum induces cell-mediated net calcium efflux from bone and increases beta-glucuronidase release. Calcitonin inhibits the increase in both calcium efflux and beta-glucuronidase release, suggesting that aluminum stimulates osteoclasts to release bone mineral.

Effects of parathyroid hormone on net proton flux from neonatal mouse calvariae

1987 ◽  
Vol 252 (4) ◽  
pp. F585-F589 ◽  
Author(s):  
D. A. Bushinsky
Keyword(s):  
Parathyroid Hormone ◽  
Chronic Exposure ◽  
Neonatal Mouse ◽  
Alkaline Media ◽  
Alkaline Ph ◽  
Calcium Efflux ◽  
Acute Metabolic Acidosis ◽  
Ph Range ◽  
And Control ◽  
Proton Buffering

Bone mineral buffers protons during acute metabolic acidosis; whether parathyroid hormone (PTH) augments proton buffering is controversial. To determine whether PTH augments proton buffering by bone, we cultured neonatal mouse calvariae with or without PTH (10(-8) M) for 3 h in medium that was physiologically acid (pH approximately 7.20), neutral (pH approximately 7.40), or alkaline (pH approximately 7.60). Over the entire pH range studied there was less influx of protons into calvariae treated with PTH than into control calvariae, indicating that PTH does not augment but instead inhibits proton buffering by bone. To determine whether chronic exposure to PTH is necessary to augment proton buffering, calvariae were incubated with PTH for 24 h before a 3-h culture. Calcium efflux from calvariae exposed to PTH (10(-8) M) for 24 h exceeded that of controls. When these same calvariae were recultured for 3 h in fresh medium, PTH-treated and control calvariae behaved similarly, with net efflux of protons into acid, neutral, and alkaline media. Regardless of whether PTH is added at the time of exposure to acid medium or 24 h before calvariae cultured with PTH do not buffer protons to a greater extent than controls.

Mechanism of proton-induced bone calcium release: calcium carbonate-dissolution

1987 ◽  
Vol 253 (5) ◽  
pp. F998-F1005 ◽  
Author(s):  
D. A. Bushinsky ◽  
R. J. Lechleider
Keyword(s):  
Metabolic Acidosis ◽  
Calcium Carbonate ◽  
Bone Mineral ◽  
Calcium Release ◽  
Calcium Efflux ◽  
Carbonate Phase ◽  
Bone Calcium ◽  
Calcium Carbonate Dissolution

Protons are buffered and calcium is released by bone during metabolic acidosis. Incubation of neonatal mouse calvariae in acid medium causes net calcium efflux from bone and net proton influx into bone, just as metabolic acidosis does in vivo. To determine whether the calcium carbonate phase of bone mineral is solubilized with increasing proton concentrations, we cultured calvariae for 3 h in medium in which the saturation was varied by changing pH or calcium and phosphate concentrations. We determined the driving force for crystallization by calculating the Gibbs free energy of formation (DG). With alteration of the medium pH, calcium carbonate entry or loss from bone varied linearly with the initial DG for medium calcium carbonate (r = -0.745, n = 41, P less than 0.001) as it did with alteration of the medium calcium and phosphate (r = -0.665, n = 118, P less than 0.001). There was dissolution of calcium carbonate into medium that was unsaturated with respect to calcium carbonate, net flux ceased at saturation, and calcium carbonate entered bone from supersaturated medium, indicating that the medium is in equilibrium with the calcium carbonate phase of bone mineral. Neither the mineral phase brushite nor apatite was in equilibrium with the medium. These observations indicate that in vitro, acute proton-induced calcium efflux is due to dissolution of bone calcium carbonate.

Importance of medullary events in ammonium excretion: studies in acute respiratory and acute metabolic acidosis

1983 ◽  
Vol 61 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Andre Gougoux ◽  
Patrick Vinay ◽  
Guy Lemieux ◽  
Marc Goldstein ◽  
Bobby Stinebaugh ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Collecting Duct ◽  
Respiratory Acidosis ◽  
Renal Medulla ◽  
Hydrogen Ion ◽  
Ammonium Excretion ◽  
Urine Ph ◽  
Ion Secretion ◽  
Medullary Collecting Duct ◽  
Acute Metabolic Acidosis

The renal medulla can play an important role in acid excretion by modulating both hydrogen ion secretion in the medullary collecting duct and the medullary [Formula: see text]. The purpose of these experiments was to characterize the intrarenal events associated with ammonium excretion in acute acidosis. Cortical events were monitored in two ways: first, the rates of glutamine extraction and ammoniagenesis were assessed by measuring arteriovenous differences and the rate of renal blood flow; second, the biochemical response of the ammoniagenesis pathway was examined by measuring glutamate and 2-oxoglutarate, key renal cortical metabolites in this pathway. There were no significant differences noted in any of these cortical parameters between acute respiratory and metabolic acidosis. Despite a comparable twofold rise in ammonium excretion in both cases, the urine pH, [Formula: see text], and the urine minus blood [Formula: see text] difference (U-B [Formula: see text]) were lower during acute hypercapnia. In these experiments, the urine [Formula: see text] was 34 mmHg (1 mmHg = 133.322 Pa) lower than that of the blood during acute respiratory acidosis while the U-B [Formula: see text] was 5 ± 3 mmHg in acute metabolic acidosis. Thus there were significant differences in medullary events during these two conditions. Although the urine pH is critical in determining ammonium excretion in certain circumstances, these results suggest that regional variations in the medullary [Formula: see text] can modify this relationship.

Renal ammoniagenesis following glutamine loading in intact dogs during acute metabolic acid–base perturbations

1987 ◽  
Vol 72 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Jorge Areas ◽  
Sevag Balian ◽  
Dianna Slemmer ◽  
Mario Belledonne ◽  
Harry G. Preuss
Keyword(s):  
Blood Flow ◽  
Glomerular Filtration Rate ◽  
Metabolic Acidosis ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Respiratory Acidosis ◽  
Glutamine Metabolism ◽  
Acid Base ◽  
Acute Metabolic Acidosis ◽  
Qualitative Changes

1. Adaptation of renal ammoniagenesis during acute metabolic acidosis in intact dogs may be nonexistent or, at least, markedly less than in chronic acidosis. This contrasts to adaptation in acute respiratory acidosis, where levels similar to those attained in chronic acidosis occur within hours. 2. Accordingly, the inability to discern marked changes in acute metabolic acidosis compared with acute respiratory acidosis has been attributed to decreased glomerular filtration rate and renal blood flow seen frequently in the former. 3. In our studies, we found early changes in ammoniagenesis and glutamine metabolism during acute metabolic acidosis, but not of the magnitude seen in chronic acidosis, even considering the changes in renal blood flow (RBF) and glomerular filtration rate (GFR). Exogenous glutamine loading allowed us to discover that the qualitative changes in glutamine metabolism during acute metabolic acidosis differed from control but fell short of those seen in chronic metabolic a acidosis. 4. We also examined glutamine metabolism when renal ammoniagenic adaptation was acutely inhibited in chronically acidotic dogs. Infusing NaHCO3 into chronically acidotic dogs decreased renal ammonia production significantly (247 μmol min−1 100 ml−1 GFR vs 148 μmol min−1 100 ml−1 GFR: P < 0.001) and glutamine extraction (111.8 μmol min−1 100 ml−1 GFR vs 90.9 μmol min−1 100 ml−1 GFR: P < 0.02). 5. The qualitative changes in renal glutamine metabolism in both studies suggest that alterations in deamination of glutamate formed from glutamine are responsible, at least in part, for adaptation to acute acid–base perturbations. 6. Compared with respiratory acidosis, adaptation to metabolic acidosis is progressive and prolonged.

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