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The influx of calcium ions into human erythrocytes during cold storage.

ABSTRACT: 1. When human erythrocytes, suspended in iso-osmotic sucrose containing CaCl(2), are stored at 3 degrees C, Ca(2+) influx into the cells occurs. Simultaneously, efflux of K(+), Na(+), Cl(-) and water takes place and cell volume diminishes. 2. The extent of Ca(2+) influx increases with duration of cold storage and with increasing concentration of Ca(2+) in the suspending medium. 3. Erythrocytes that have been thus loaded with Ca(2+) exhibit Ca(2+) efflux against a concentration gradient when subsequently incubated at 37 degrees C. 4. Ca(2+) influx likewise occurs when the sucrose of the medium is replaced by iso-osmotic solutions of other non-ionized compounds. 5. Replacement of sucrose by iso-osmotic KCl or NaCl greatly diminishes the rate of Ca(2+) influx during cold storage; however, in iso-osmotic choline chloride, Ca(2+) influx is as rapid as in sucrose. 6. Preincubation of erythrocytes in iso-osmotic sucrose at 37 degrees C causes rapid efflux of K(+) and Na(+) and renders the cell membranes highly permeable to Ca(2+) during subsequent cold storage. 7. Preincubation of erythrocytes in iso-osmotic NaCl at 37 degrees C with trypsin or neuraminidase is without effect on the permeability of the membrane towards Ca(2+). 8. The experimental results lead to the conclusion that the main prerequisite for Ca(2+) influx into erythrocytes is the partial depletion of the cells of their univalent cations.

SUBMITTER: Long C

PROVIDER: S-EPMC1177621 | biostudies-other | 1973 Mar

REPOSITORIES: biostudies-other

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Project description:Propionibacterium freudenreichii is used as a ripening culture in Swiss cheese manufacture. It produces flavor compounds over the whole ripening period. During cheese ripening, P. freudenreichii is exposed to a temperature downshift, especially when cheeses are transferred from warm temperature (about 24°C) to cold temperature (about 4°C). The aim of this study was to investigate the adaptation of P. freudenreichii at cold temperature by means of the first global gene expression profile for this species. The temporal transcriptomic response of P. freudenreichii was analyzed at five times of growth, during growth at 30°C then for 9 days at 4°C, in the constant presence of lactate as the main carbon source. P. freudenreichii response was also investigated by RT-qPCR for 30 genes, by proteomics and metabolomics (main metabolites quantified in culture supernatant). Microarray analysis revealed that 565 genes (25% of the protein-coding sequences of P. freudenreichii genome) were differentially expressed during transition from warm to cold temperature (P < 0.05 and |fold change| > 1). Most of the down-expressed genes were involved in cell machinery (cell division, protein turnover, translation, transcription and DNA replication). During incubation at cold temperature, P. freudenreichii accumulated carbon supplies by up-regulating genes involved in lactate, alanine and serine conversion to pyruvate, in gluconeogenesis and in glycogen synthesis. Interestingly, some genes involved in the formation of important flavor compounds of cheese, coding for an extracellular lipolytic esterases and enzymes of the pathways of formation of branched-chain compounds, were not significantly affected by cold. In conclusion, P. freudenreichii is metabolically active at cold temperature and induces pathways to maintain its long-term viability, which could explain its contribution to cheese ripening even at low temperature. Gene expression was measured in the middle of exponential growth phase at 30°C (20 h, OD650 ≈ 0.5), at the end of exponential growth phase (40 h, OD650 ≈ 2), and after 3, 6 and 9 days of incubation at 4°C. Three independent biological experiments were performed at each time (20h, 40h, 3, 6 and 9 days) and labelled A, B, C. One technical repetition was performed using the RNA of the 20HA sample ; This technical repetition was labelled 20HAbis.

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The influx of calcium ions into human erythrocytes during cold storage.

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