Abstract
$PGE_2$ and $PGF_{2{\alpha}}$ 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 $PGF_{2{\alpha}}$ 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 $PGF_{2{\alpha}}$. The present study was undertaken to elucidate mechanisms of action of $PGE_2$ and $PGF_{2{\alpha}}$ 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) $PGE_2$ and $PGF_{2{\alpha}}$ increased osmotic fragility at concentrations above $10^{11}\;M$, the effect being similar for both hormones. The concentration of NaCl for 100% hemolysis was $1/16{\sim}1/17\;M$ in the presence of $10^{11}\;M\;PGE_2$ or $PGF_{2{\alpha}}$ and 1/18 M in the absence of the hormone (control). 2) When erythrocytes were suspended in 1/15 M NaCl solution, $44.2{\pm}4.3%$ of cells were hemolyzed. Addition of $10^{12}\;M\;PGE_2$ or $PGF_{2{\alpha}}$ 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 $10^{11}\;M\;PGE_2$ and $PGF_{2{\alpha}}$ appeared to he identical regardless of absence or presence of $Ca^{++}\;(0.5{\sim}10\;mM)$ 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 $10^{11}\;M\;PGE_2$ or $PGF_{2{\alpha}}$, 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, $PGE_2$ and $PGF_{2{\alpha}}$ 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 $PGE_2$ and $PGF_{2{\alpha}}$, 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.
$PGE_2$ 및 $PGF_{2{\alpha}}$가 용혈 및 적혈구막 절편에서 $Ca^{++}$ 결합에 미치는 영향을 관찰하여 다음과 같은 결론을 얻었다. 1) $PGF_{2{\alpha}}$는 $PGE_2$와 같이 적혈구막 삼투성 취약성을 증가시키는데 대조군에서는 NaCl농도 1/18 M 용액에서 완전히 용혈되었으나 $PGE_2$ 및 $PGF_{2{\alpha}}$ 가 $10^{11}M$ 이상 포함될 경우 NaCl농도 $1/16{\sim}1/17\;M$ 에서 100 % 용혈이 일어났다. 2) 동일한 적혈구 부유액을 사용할 때 NaCl농도 1/15 M 용액에서 대조군은 $44.2{\pm}4.3%$가 용혈되나 $PGE_2$ 및 $PGF_{2{\alpha}}$가 $10^{11}M$농도로 포함되었을 때 용혈은 각기 $73.6{\pm}8.4%$ 및 $68.7{\pm}6.4%$로 대조군에 비하여 의의있게 증가하였으며 그 이상의 농도에서는 더 이상 증가를 보이지 않았다. 3) $PGE_2$ 및 $PGF_{2{\alpha}}$에 의해 증가된 용혈은 어느 $Ca^{++}$농도에서도 대조군보다 항상 일정한 정도로 증가되어 있다. 4) 적혈구막 절편에서의 $Ca^{++}$결합은 대조군이나 $PGE_2$ 및 $PGF_{2{\alpha}}$처치군 모두 incubation용액내 $Ca^{++}$농도가 증가함에 따라 곡선적으로 증가하여 $Ca^{++}$농도 5 mM에서 포화된다. 그러나 같은 농도의 $Ca^{++}$에서 비교할 때 적혈구막의 $Ca^{++}$결합은 $PGE_2$ 및 $PGF_{2{\alpha}}$ 존재시 대조군에 비하여 의의있게 증가되었다. 이상의 결과로 보아 $PGE_2$ 및 $PGF_{2{\alpha}}$가 적혈구막의 삼투성 취약성을 증가시키는 기전은 $Ca^{++}$과는 독립적으로 작용함을 알 수 있다.