Increase In Cytoplasmic Free Calcium Concentration Research Articles

Genome-Wide Identification and Expression Profile of OSCA Gene Family Members in Triticum aestivum L.

Hyperosmolality and various other stimuli can trigger an increase in cytoplasmic-free calcium concentration ([Ca2+]cyt). Members of the Arabidopsis thaliana (L.) reduced hyperosmolality-gated calcium-permeable channels (OSCA) gene family are reported to be involved in sensing extracellular changes to trigger hyperosmolality-induced [Ca2+]cyt increases and controlling stomatal closure during immune signaling. Wheat (Triticum aestivum L.) is a very important food crop, but there are few studies of its OSCA gene family members. In this study, 42 OSCA members were identified in the wheat genome, and phylogenetic analysis can divide them into four clades. The members of each clade have similar gene structures, conserved motifs, and domains. TaOSCA genes were predicted to be regulated by cis-acting elements such as STRE, MBS, DRE1, ABRE, etc. Quantitative PCR results showed that they have different expression patterns in different tissues. The expression profiles of 15 selected TaOSCAs were examined after PEG (polyethylene glycol), NaCl, and ABA (abscisic acid) treatment. All 15 TaOSCA members responded to PEG treatment, while TaOSCA12/-39 responded simultaneously to PEG and ABA. This study informs research into the biological function and evolution of TaOSCA and lays the foundation for the breeding and genetic improvement of wheat.

Effects of inhibin on activin A-Induced glucose metabolism in rat hepatocytes

This study was conducted to investigate the effects of inhibin on hepatic glucose metabolism. We have previously reported that activin A induced a dose-dependent glycogenolytic action on hepatocytes, and that 10(-9) M activin A induced a maximum glycogenolytic effect. Inhibin itself induced no increase or decrease in glucose output at any dose tested. At a concentration of 10(-10) M, inhibin was seen to inhibit 10(-9) M activin A-induced glucose output by 30% as compared to the control. In contrast to its inhibitory effect on the action of activin A, 10(-10) M and higher concentrations of inhibin did not inhibit angiotensin II-or vasopressin-induced glycogenolysis. We further investigated the mechanism of the inhibitory effect of inhibin on activin A-induced glycogenolysis, and found that 10(-10) M inhibin did inhibit the increase in cytoplasmic-free calcium concentration that was seen with 10(-9) M activin A.We also investigated the effects of inhibin on the activin A-induced production of inositol trisphosphates, and the results showed that 10(-10) M inhibin inhibited the activin A-induced production of inositol trisphosphates by 30% compared to the control. Furthermore, it was demonstrated that inhibin did not affect the binding of activin A to isolated hepatocytes. These data demonstrated that inhibin inhibited the activin A-induced glycogenolysis by inhibiting the increases of inositol trisphosphates and cytoplasmic free calcium concentrations.

Initiation of insulin secretion in glucose-free medium by activin A

Activin A is a multifunctional protein known to stimulate insulin secretion (Yasuda H et al., (1993) Endocrinology 133, 624–630). The present study was conducted to determine whether activin A augments insulin secretion in the absence of ambient glucose. In the presence of 2.7 mM glucose, and 1.25 mM calcium, activin A induced a biphasic secretory reponse of insulin. In the absence of glucose in perifusate, activin A induced a small but significant release of insulin. The effect of activin A was monophasic in the absence of glucose. In contrast, glucagon-like peptide-1 (GLP-1) had no effect on insulin secretion under the same conditions. However, GLP-1 could enhance insulin secretion induced by activin A in glucose-free medium. Activin A induced a transient increase in cytoplasmic-free calcium concentration, [Ca 2+] c, in a fura-2-loaded islet superfused with glucose-free buffer. Again, GLP-1 was without effect on [Ca 2+] c by itself in glucose-free buffer. In the presence of activin A, however, GLP-1 could induce an elevation of [Ca 2+ c. Finally, GLP-1, but not activin A, increased cAMP content in islets incubated in glucose-free medium. These results indicate that activin A, but not GLP-1, induces insulin secretion in glucose-free medium. Activin A is able to reproduce partly the effect of glucose to support the action of GLP-1 in glucose-free medium.