Nucleotides가 세포막 투과도에 미치는 영향

Effects of Various Nucleotides on the Membrane Permeability

The present study was designed to investigate i) the action of various nucleotides on membrane permeability of rat red blood cell and hepatocyte for Na⁺ and Rb⁺ ii) the characteristics of purinoceptors on these cell membranes. Blood from Sprague-Dawley rats was obtained by carotid arterial cannulation. Red blood cells were then washed 3 times with saline at 4˚C. Hepatic parenchymal cells were isolated from rat livers by using a modification of the Berry and Friend (1969) method. For the Na⁺ influx studies, isolated RBC and hepatocyte were incubated in incubation medium containing ²²Na⁺0.2 μCi/ml at 37℃. After various time intervals samples were removed from the incubation flask and washed out 3 times with ice-cold washing solutions. Cells were destroyed by adding Triton X-100 and TCA solution. After centrifugation, the supernatants were assayed for ²²Na⁺ by gamma counter. ⁸⁶Rb⁺ was used to simulate K⁺ in these K⁺efflux studies. Isolated hepatocytes were incubated for 60 min in the loading solution containing ⁸⁶Rb⁺ 10 μCi/ml at 37℃. After loading, the cells washed out 3 times by centrifugation with washing solution. The cells were incubated in buffer solution at 37℃. At intervals thereafter, samples were removed and centrifuged. The supernatants were analyzed for ⁸⁶Rb⁺ by liquid scintillation counter. The main results of the experiments were: 1) ATP and ATPP increased in both ²²Na⁺ influx and ⁸⁶Rb⁺ efflux in the red blood cell. Although ADP showed a tendency to increase in RBC membrane permeability for ²²Na⁺ and ⁸⁶Rb⁺, the changes were not significantly different from the control. 2) The Significant changes in ²²Na⁺ and ⁸⁶Rb⁺ flux by ATP were also demonstrated in hepatocyte. ATPP and ADP showed a tendency to increase in hepatocyte membrane permeability for both ions. 3) Other nucleoside triphosphates-ITP, GTP and CTP-did not change in membrane permeability for ²²Na⁺ and ⁸⁶Rb⁺ in RBC and hepatocyte. In conclusion, not only ATP but also ATPP activate purinoceptors and change in membrane permeability for Na⁺ and K⁺. In order to activate purinoceptors on the cell membrane, the nucleotides have to possess intact adenine moiety and three phosphates or more in its molecule.