Non-mitochondrial calcium uptake and release by chondrocyte: Role of ATP, phosphate ions and inositol triphosphate.:Role of ATP, phosphate ions and inositol triphosphate

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The objective of this investigation was to evaluate Ca2+ binding characteristics of the endoplasmic reticulum of chick chondrocytes. Using a permeabilized cell preparation in which Ca2+ uptake into mitochondria was blocked with ruthenium red, we measured cation uptake by a rapid centrifugation procedure. In terms of Ca2+ binding, we demonstrated that uptake was mediated by ATP and blocked by treatment with vanadate. To determine whether or not Ca2+ binding proteins existed in these cells we isolated endoplasmic reticulum from chondrocytes. Using a 45Ca overlay technique, we demonstrated the presence of Ca2+ binding proteins that were of the same size as the reticuloplasmins. We measured Ca2+ release characteristics of avian chondrocyte endoplasmic reticulum. The cells were sensitive to 1, 4, 5-inositol triphosphate (IP3)-the rate and extent of Ca2+ release from this pool was similar in magnitude to that of other tissues. To evaluate the effects of metabolic factors on cation transport, we examined the effect of glucose, glucose 6-phosphate and inorganic phosphate (Pi). We noted that there was minimal phosphatase activity and exogenous glucose 6-phosphate did not stimulate Ca2+ transport. However, Pi markedly increased ATP supported Ca2+ uptake. This finding suggests that any mechanism that could serve to elevate the intracellular Pi concentration, whether by hydrolysis of organic phosphate esters or by supplementing the cytosolic Pi concentration, would serve to maintain Ca2+ within the endoplasmic reticulum. The results of these studies indicate a central role of intracellular Pi in chondrocyte Ca2+ transport.
歯科基礎医学会の論文

Non-mitochondrial calcium uptake and release by chondrocyte: Role of ATP, phosphate ions and inositol triphosphate.:Role of ATP, phosphate ions and inositol triphosphate

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歯科基礎医学会 | 論文

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