Gentamicin이 적혈구막을 통한 Na+ 이동에 미치는 영향

Abstract

[한글]

Aminoglycoside 항생제의 일종인 gentamicin(GM)은 그람음성균 치료에 널리 사용되나 이 항생제를 장기간 사용시에는 부작용으로 신독성과 내이독성이 나타난다(Bonnet등, 1976;Gary등, 1976; Kaloyanides 및 Pastoriza-Munoz, 1980).

독성발생은 세포의 괴사 또는 막효소의 억제가 그 원인이 될 수 있다고 한다. 즉 GM은 guinea pig cochlea의 stria vascularis와 spiral ligament에 존재하는 총 ATPase활성도와 Na**+-K**+-ATPase의 활성도를 억제하며, 개의 신장의 Na**+-K**+-ATPase활성도도 neo mycin에 의해 억제되고 (Lipsky 및 Lietman, 1980), guinea pig의 신장 피질과 수질의 microsome 분획의 Na**+-K**+-ATPase 활성도도 aminoglycoside 항생제에 의해 현저히 억제되며(Chahwala 및 Harpur, 1982) 사람의 적혈구막에 존재하는 Ca**++-ATPase 활성도(박 등, 1986)와 Na**+-K**+-ATPase활성도(Chahwala및 Harper, 1982) 모두 GM에 의해 억제된다는 것이 보고되었다.

따라서 본 실험에서는 세포막의 Na**+-K**+-ATPase활성도를 억제하는 것으로 알려진 GM이 세포막을 경계로 Na**+과 K**+의 이동 및 적혈구막의 (3)**H-ouabain결합에 미치는 영향을 관찰하여 다음과 같은 결론을 얻었다.

1) GM은 적혈구막 소편의 막효소인 Na**+-K**+-ATPase의 활성도를 억제시켰으며, 그 억제효과는 GM의 농도에 비례하였다.

2) 적혈구막을 통한 능동적인 (22)**Na유출은 GM에 의해 억제되었으며 ouabain과 GM을 동시에 첨가시 각각의 약물을 단독으로 첨가시보다 억제효과가 더 크게 나타났다.

3) GM은 능동적인 (86)**Rb유입을 억제시켰으며, ouabain과 GM을 동시에 첨가하였을때 그 억제효과는 GM 단독첨가시와 유사하였다.

4) GM은 적혈구막에서 (3)**H-ouabain 결합을 증가시켰다. 이상의 성적으로 미루어 볼때 GM에 의한 능동적인 (22)**Na유출과 (86)**Rb유입의 억제는 막효소인 Na**+-K**+-ATPase 활성도의 감소와 적혈구막에서 (3)**H-ouabain 결합의 증가에 기인한다고 생각된다.

[영문]

Gentamicin(GM) is a polybasic, aminoglycoside antibiotic used frequently for the treatment of serious gram-negative infections. The major limiting factors in the clinical use of GM, as well as other aminoglycoside antibiotics are their nephrotoxicity and ototoxicity. The primary mechanism of cell injury in aminoglycoside toxicity appears to be the disruption of normal membrane function and the inhibition of Na**+-K**+-ATPase activity.

There is both indirect and direct evidence which suggests that the effect of aminoglycoside antibiotics on Na**+-K**+-ATPase may explain, or contribute to, their toxicity. It has been shown that aminoglycoside reduce total ATPase activity (Kaku et al., 1973) and Na**+-K**+-ATPase activity(linuma et al., 1967) in the stria vascularis and spiral ligament of the guinea pig cochlea. Lipsky and Lietman(1980) demonstrated dose dependent inhibition of canine renal Na**+-K**+-ATPase by neomycin. Chahwala and Harper(1757) reported that aminoglycoside antibiotics inhibited the activity of Na**+-K**+-ATPase in microsomal fractions of the cortex and medulla of the guinea pig kidney, isolated rat renal tubule and human erythrocyte ghosts.

The present investigation was undertaken to elucidate the mechanism of GM on human erythrocytes by examining its effect on Na**+-K**+-ATPase activity, active sodium and potassium transport across red blood cell and (3)**H-ouabain binding to red blood cell membranes.

The results obtained are summarized as follows:

1) GM inhibited significantly both the activity of total ATPase and Na**+-K**+-ATPase at all concentrations tested.

2) GM inhibited active (22)**Na efflux across red blood cell. When ouabain is present, the rate of (22)**Na efflux was completely inhibited. When both GM and ouabain were added, the inhibitory effect of active (22)**Na efflux was more pronounced.

3) Active (86)**Rb influx was inhibited significantly by GM In the presence of ouabain, the rate of (86)**Rb influx is markedly inhibited. But (86)**Rb influx is not appreciably altered by the presence of both GM and ouabain.

4) In the presence of GM, (3)**H-ouabain binding to red blood cell membrane increased.

From the above results, it may be concluded that the inhibition of active sodium and potassium transport across red blood cell by gentamicin appears to be due to the inhibition of Na**+-K**+-ATPase activity and an increase in ouabain binding to red blood cell membranes.