PGE₂ 및 PGE_2α가 삼투성 용혈 및 적혈구막 Ca⁺⁺결합에 미치는 영향

Effect of PGE₂ and PGE_2α on the Osmotic Fragility and Membrane Ca⁺⁺ Binding in Human Erythrocytes

PGE₂ 및 PGF_2α가 용혈 및 적혈구막 절편에서 Ca⁺⁺ 결합에 미치는 영향을 관찰하여 다음과 같은 결론을 얻었다. 1)PGF_2α는 PGE₂와 같이 적혈구막 삼투성 취약성을 증가시키는데 대조군에서는 NaCl농도 1/18 M 용액에서 완전히 용혈되었으나 PGE₂ 및 PGF_2α 가10^-11 이상 포함될 경우 NaCl농도 1/16 ~ 1/17 M 에서 100 % 용혈이 일어났다. 2) 동일한 적혈구 부유액을 사용할 때 NaCl농도 1/15 M 용액에서 대조군은 44.2±4.3%가 용혈되나 PGE₂ 및 PGF_2α가 10^-11M농도로 포함되었을 때 용혈은 각기 73.6±8.4% 및 68.7±6.4%로 대조군에 비하여 의의있게 증가하였으며 그 이상의 농도에서는 더 이상 증가를 보이지 않았다. 3) PGE₂ 및 PGF_2α에 의해 증가된 용혈은 어느 Ca⁺⁺농도에서도 대조군보다 항상 일정한 정도로 증가되어 있다. 4) 적혈구막 절편에서의 Ca⁺⁺결합은 대조군이나 PGE₂ 및 PGF_2α처치군 모두 incubation용액내 Ca⁺⁺농도가 증가함에 따라 곡선적으로 증가하여 Ca⁺⁺농도 5 mM에서 포화된다. 그러나 같은 농도의 Ca⁺⁺에서 비교할 때 적혈구막의 Ca⁺⁺결합은 PGE₂ 및 PGF_2α 존재시 대조군에 비하여 의의있게 증가되었다. 이상의 결과로 보아 PGE₂ 및 PGF_2α가 적혈구막의 삼투성 취약성을 증가시키는 기전은 Ca⁺⁺과는 독립적으로 작용함을 알 수 있다.

PGE₂ and PGF_2α are known to act similarly in a number of animal tissues. They both facilitate regression of corpus luteum(Poyser, 1972; Fuch et al, 1974; Coudert et at, 1974) and stimulate contraction of uterine muscle (Laudanski et al, 1977; Porter et al, 1979; Hollingsworth et al, 1980). It is, however, not known whether these two prostaglandins exert similar actions in osmotic fragility of erythrocytes (Rasmussen et al, 1975) and PGF_2α alters conformation of membrane proteins (Meyers aud Swislocki, 1974). The former effect may not be mediated through changes in c- AMP concentration in the cell, since the adenylate cyclase activity in human erythrocyte is extremely low (Rodan et al, 1976; Sutherland et al, 1962) and the latter effect implies that physical state (or fluidity) of the membrane is altered by PGF_2α. The present study was undertaken to elucidate mechanisms of action of PGE² and PGF_2α on the human erythocyte membrane by examining their effects on osmotic fragility and Ca⁺⁺ binding to the membrane fragments. The results are summarized as follows: 1) PGE₂ and PGF_2α increased osmotic fragility at concentrations above 10^-11 M , the effect being similar for both hormones. The concentration of NaCl for 100% hemolysis was 1/16 ~ 1/17 M in the presence of 10^-11 M PGE₂ or PGF_2α and 1/18 M in the absence of the hormone (control). 2) When erythrocytes were suspended in 1/15 M NaCl solution, 44.2±4.3% of cells were hemolyzed. Addition of 10^-12 M PGE₂ or PGF_2α did not increase hemolysis. When the concentration of the hormones was increased to 10^-11 M , however the degree of hemolysis increased markealy to about 80%. No further increase in hemolysis was observed at concentration of the hormones above 10^-11 M . 3) The additional hemolysis due to 10^-11 M PGE₂ and PGF_2α appeared to he identical regardless of absence or presence of Ca⁺⁺ (0.5 ~ 10 mM) in the suspending medium. 4) In the absence of prostaglandin, the binding of Ca⁺⁺ to the erythrocyte membrane increased curvilinearly as the Ca⁺⁺ concentration increased up to 5 mM above which it leveled off. A similar dependence of Ca⁺⁺ binding on the Ca⁺⁺ concentration was observed in the presence of 10^-11 M PGE₂ or PGF_2α, however, the amount of Ca⁺⁺ bound at a given Ca⁺⁺ concentration was significantly higher than in the absence of the hormones. 5) As in the hemolysis, PGE₂ and PGF_2α did not affect the Ca⁺⁺ binding at a concentration of 10^-12 M , but increased it by about 100% at concentration above 10^-11 M . These result indicate that both tile osmotic fragility of erythrocyte and the Ca⁺⁺ binding to the erythrocyte membrane are similarly enhanced by PGE₂ and PGF_2α, but these two effects are not causally related. It is, therefore, concluded that the prostaglandin-induced hemolysis is not directly associated with alterations of the Ca⁺⁺ content in the membrane.