The role of inositol 1,4,5-trisphosphate in mobilizing calcium from intracellular stores in the salivary glands of Amblyomma americanum (L.) |
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Institution: | 1. Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland;2. Department of Bioinformatics, Adam Mickiewicz University in Poznan, Umultowska 89, 61-614 Poznan, Poland |
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Abstract: | Isolated tick salivary glands, permeabilized with digitonin in the presence of the Ca2+ uptake inhibitors, sodium azide and vanadate, released Ca2+ in response to 20 μM inositol-1,4,5-trisphosphate (IP3). Inositol-1-phosphate (IP1) and inositol-1,4-bisphosphate (IP2) appeared to stimulate an uptake of Ca2+ into whole glands. Inositol-1,4,5-trisphosphate caused release of Ca2+ from a 100,000 g microsome enriched pellet; however, IP1 and IP2 were ineffective in stimulating an uptake or efflux of Ca2+. The combined 900 and 11,500 g pellets showed no significant release of Ca2+ in response to addition of IP3. Inositol-1,4,5-trisphosphate concentrations as low as 1 μM are capable of stimulating a significant release of Ca2+ from microsomes. Results suggest that intracellular Ca2+ is mobilized from microsomal intracellular stores in response to agonists which increase cytosolic IP3 in tick salivary glands. Results also suggest a possible role for IP1 and IP2 or both in stimulating an uptake of Ca2+ into vanadate and azide-insensitive intracellular pools. |
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