Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
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Little attention has been given to the consequences of the in vivo calcium status on intracellular calcium homeostasis despite the fact that chronic states of hypo- or hypercalcemia are often observed in humans at all ages. The aim of the studies was to probe the influence of an in vivo calcium deficiency on the resting cytoplasmic Ca2+ concentration ([Ca2+]c] and the IP3-sensitive Ca2+ pools and to investigate the effect of calcium repletion in the presence or absence of the vitamin D3 hormone 1,25(OH)2 D3 on these pools. Studies were conducted in hepatocytes isolated from normal(N), calcium deficient rats (Ca-), hypocalcemic rats supplemented with oral calcium alone (Ca+) or 1,25(OH)2 D3 (1,25(OH)2 D3+). Both resting [Ca2+]c and Ca2+ mobilization from the IP3-sensitive cellular pool were significantly lowered by calcium depletion. In addition, Ca- was shown to significantly reduce calreticulin mRNA and protein levels. The effects of calcium deficiency on cellular calcium homeostasis were all found to be reversible by repletion with oral calcium feeding or by the administration of the calcium-regulating hormone 1,25(OH)2 D3. These data indicate that, despite the large calcium gradient between extra- and intracellular calcium concentration, calcium deficiency in vivo significantly alters cellular calcium homeostasis. These observations have important impact in our understanding of several pathologies associated with a sub-optimal calcium status.

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Poster Number PAmailhot, g.0404
Keywords: Hypocalcemia, [Ca2+] i, IP3, Calreticulin, Vitamin D3