• Development and Reproduction
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• v.3 no.1
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• pp.87-93
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• 1999

The possible role of Na$^{+}$/H$^{+}$ antiporter in both the capacitation and the acrosome reaction (AR) was examined in mouse epididymal spermatozoa. Spontaneous acrosome reaction was inhibited by dimethyl amiloride (DMA), a specific inhibitor of Na$^{+}$/H$^{+}$ antiporter, with dose dependent manner. Follicular fluid- or A23l 87-induced acrosome reaction was not inhibited by DMA. It suggests that change in pH$_{i}$ by monovalent cation transport through the Na$^{+}$/H$^{+}$ antiporter is possibly engaged in the capacitation and that agonist- as well as A23l87-induced AR in capacitated sperm might be independent from the Na$^{+}$/H$^{+}$ antiporter. Conclusively, changes in pH$_{i}$ through the Na$^{+}$/H$^{+}$ antiporter might be important for sperm capacitation and it virtually occurs upstream of the $Ca^{2+}$ influx which precedes the acrosome reaction in mouse epididymal spermatozoa.pididymal spermatozoa.

• Plant Biotechnology Reports
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• v.4 no.1
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• pp.15-21
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• 2010

The over-expression of Arabidopsis CAX1 and CAX2 causes transgenic tomato plants to reveal severe $Ca^{2+}$ deficiency-like symptoms such as tip-burn and/or blossom end rot, despite there being sufficient $Ca^{2+}$ in each plant part. To correct the symptoms and to moderately enhance the calcium level, a worldwide vegetable tomato was genetically engineered using a modified Arabidopsis cation/$H^+$ antiporter sCAX2A, a mutant form of Arabidopsis CAX2. Compared with the wild-type, the sCAX2A-expressing tomato plants demonstrated elevated $Ca^{2+}$ levels in the fruits with almost no changes in the levels of $Mn^{2+}$, $Cu^{2+}$, and $Fe^{2+}$. Moreover, expression of sCAX2A in tomato plants did not show any significant alterations in their morphological phenotypes. Unlike 35S::sCAX1 construct, sCAX2A antiporter gene driven by 35S promoter can be a valuable tool for enriching $Ca^{2+}$ contents in the tomato fruit without additional accumulation of the undesirable cations.

• The Korean Journal of Physiology and Pharmacology
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• v.6 no.1
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• pp.21-26
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• 2002

Effects of cadmium (Cd) intoxication on renal endosomal accumulation of organic cations $(OC^+)$ were studied in rats using $^{14}C-tetraethylammnium$ (TEA) as a substrate. Cd intoxication was induced by s.c. injections of 2 mg Cd/kg/day for $2{\sim}3$ weeks. Renal cortical endosomes were isolated and the endosomal acidification (acridine orange fluorescence change) and TEA uptake (Millipore filtration technique) were assessed. The TEA uptake was an uphill transport mediated by $H^+/OC^+$ antiporter driven by the pH gradient established by $H^+-ATPase.$ In endosomes of Cd-intoxicated rats, the ATP-dependent TEA uptake was markedly attenuated due to inhibition of endosomal acidification as well as $H^+/TEA$ antiport. In kinetic analysis of $H^+/TEA$ antiport, Vmax was reduced and Km was increased in the Cd group. Inhibition of $H^+/TEA$ antiport was also observed in normal endosomes directly exposed to free Cd (but not Cd-metallothionein complex, CdMt) in vitro. These data suggest that during chronic Cd exposure, free Cd ions liberated by lysosomal degradation of CdMt in proximal tubule cells may impair the endosomal accumulation of $OC^+$ by directly inhibiting the $H^+/OC^+$ antiporter activity and indirectly by reducing the intravesicular acidification, the driving force for $H^+/OC^+$ exchange.

• Biomolecules & Therapeutics
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• v.25 no.4
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• pp.441-451
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• 2017

Imperatorin, a major bioactive furanocoumarin with multifunctions, can be used for treating neurodegenerative diseases. In this study, we investigated the characteristics of imperatorin transport in the brain. Experiments of the present study were designed to study imperatorin transport across the blood-brain barrier both in vivo and in vitro. In vivo study was performed in rats using single intravenous injection and in situ carotid artery perfusion technique. Conditionally immortalized rat brain capillary endothelial cells were as an in vitro model of blood-brain barrier to examine the transport mechanism of imperatorin. Brain distribution volume of imperatorin was about 6 fold greater than that of sucrose, suggesting that the transport of imperatorin was through the blood-brain barrier in physiological state. Both in vivo and in vitro imperatorin transport studies demonstrated that imperatorin could be transported in a concentration-dependent manner with high affinity. Imperatorin uptake was dependent on proton gradient in an opposite direction. It was significantly reduced by pretreatment with sodium azide. However, its uptake was not inhibited by replacing extracellular sodium with potassium or N-methylglucamine. The uptake of imperatorin was inhibited by various cationic compounds, but not inhibited by TEA, choline and organic anion substances. Transfection of plasma membrane monoamine transporter, organic cation transporter 2 and organic cation/carnitine transporter 2/1 siRNA failed to alter imperatorin transport in brain capillary endothelial cells. Especially, tramadol, clonidine and pyrilamine inhibited the uptake of [$^3H$]imperatorin competitively. Therefore, imperatorin is actively transported from blood to brain across the blood-brain barrier by passive and carrier-mediated transporter.

• Korean Journal of Plant Resources
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• v.21 no.5
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• pp.388-394
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• 2008

This study was carried out to develop new cultivars using the $T_5$ generation of transformed rice by PCR analysis with DNA marker in each generation $(from\;T_3\;to\;T_5)$. In the previous study, we successfully developed the transgenic rice plants over-expressing the Arabidopsis $H^+/Ca^{2+}$ antiporter CAX 1 (accession no. U57411) gene. The calcium concentration in brown rice of transgenic plants was higher than that of donor plants, Iipum, and was selected 3 lines out of 25 lines at cultured GMO field. The major agronomic traits such as culm length, panicle length and panicle number of 3 lines at transgenic plants $(T_5)$ were similar to wild type. Also these lines appeared to have disease resistance to rice blast, cold resistance as compared with donor types. The grain shape was similar to donor plant, however, the 1000 grain weight of brown rice was different from transgenic plants. These finding would be used for basic data of new variety registration.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.54 no.4
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• pp.375-383
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• 2009

This study was carried out to develop transgenic rice cultivars with the CAX1 (accession no. U57411) gene. We successfully selected the transgenic rice plants over-expressing the Arabidopsis H+/$Ca^{2+}$ antiporter CAX1 (accession no. U57411) gene in T6 generation. The brown rice of the CAX1 expressing rice contained 13.4~68.0 % more calcium $(Ca^{2+})$ than that of the wild type and 5 lines were selected based on the phenotypes compared to the control cultivar at the GMO field. The CAX1 expressing transgenic rice plants were similar in phenotype to the wild type during the whole growth period. Also these selected 4 lines appeared to be resistant to blast, cold and water solution compared with the wild type. Difference in 1,000 grain weight of brown rice was observed among each line but grain shape did not show any morphological alternations. These results suggest the enhanced Ca-substrate specificity of CAX1 exchanger in donor plant. Therefore, intact CAX1 exchanger can be functionally useful for $Ca^{2+}$ nutrient enrichment of rice with reduced accumulation of undesirable cation.