Identification of Ca2+ release channels in salivary glands secretory cells of Chironomus plumosus L.
The presence of two types of well-characterised Ca2+ release channels, namely IP3-receptors (Ins(1,4,5)P3Rs) and ryanodine-receptors (RyRs), was detected in the salivary glands secretory cells of Chironomus plumosus L. For this aim different blockators and activators of these Ca2+-transport systems were used. The conditions for permeabilization of these cells by saponine were experimentally chosen for their more intensive action.
It was shown that IP3 decreased calcium content in saponine-treated gland tissue by (41.14 ± 11.75)%. The effect of ІР3 was not observed under condition of heparin and eosin Y presence in the incubation medium, but heparin alone did not cause any action on calcium content in saponine-treated gland tissue. The observed effects of IP3 are supposed to be the evidences of Ins (1,4,5)P3Rs presence in the intracellular membrane of this object.
It was also shown that calcium content in intact gland tissue increased by (67.12 ± 22.60) % in presence of heparin (500 mkg/ml) in the incubation medium. This effect of heparin was also observed with presence of verapamil (100 mkM) and eosin Y (5, 20 mkM) in incubation medium. So, this effect is not connected with function of voltage-gated Ca2+-channels and Ca2+-pumps.
Ryanodine in concentration of 5nM decreased calcium content in saponine-treated gland tissue by (35.18 ± 3.87)% but it caused the increase of calcium content at high concentration (500 nM) by (40.72 ± 12.52)%. It improved the presence of RyRs in intracellular membrane of secretory cells of this object. Besides, these channels, perhaps, belong to “nonsensitive” to caffeine, because caffeine did not affect calcium content in the gland tissue neither in presence nor with absence of eosin Y.
Published at the site: 2004-02-02