Alteration of ${\alpha}-Adrenoceptor$ by Cd-poisoning in Rat Vas Deferens and Tail Artery

카드뮴중독이 흰쥐 정관 및 꼬리동맥의 아드레나린성 ${\alpha}-$수용체에 미치는 영향

It was aimed to elucidate the underlying mechanism which is elevated the systemic arterial blood pressure by cadmium(Cd). By using the isolated vas deferens and tail artery from Cd-poisoned rats, it was undertaken to see whether the ${\alpha}-adrenoceptor$ activity and prostaglandins action on the twitch response to electrical stimulation were altered. It was discussed in relation with sympathetic nerve activity. The response to electrical stimulation in vas deferens from Cd-poisoned rats was much enhanced, and frequency 50(Freq.50) was significantly lowered, comparing to control. However, the response of rat tail artery was attenuated by Cd. Inhibitory action of clonidine on the twitch response of vas deferens to electrical stimulation was decreased by Cd-poisoning. However, the increase in response in the presence of methoxamine was not affected. The inhibitory action of prostaglandin $E_2$ on the twitch response in the vas deferens but not in the tail artery was abolished or rather inverted by Cd-poisoning. In the tail artery from Cd-poisoned rats, the maximum contraction to methoxamine or clonidine was significantly decreased, however, $ED_{50}$ of both agonists was not changed. These results suggest that in vas deferens the autoreceptor of presynaptic membrane is inhibited by Cd-poisoning, by which mechanism the sympathetic activity is being enhanced and this alteration may be causally related to the elevation of arterial pressure.

흰쥐 정관 및 꼬리 동맥의 ${\alpha}_1-$및 ${\alpha}_2-$수용체, 그리고 prostaglandine과 관련해 NA 유리에 미치는 Cd의 영향을 관찰하여 다음과 같은 결과를 얻었다. 1. Cd 중독 흰쥐 정관에서 전기 자극에 대한 반응은 증가하였으며, Freq.50은 대조군보다 현저히 낮아졌으며 꼬리동맥의 반응은 감약되었다. 2. Cd 중독 정관에서 clonidine의 억제반응은 유의하게 감소하였으나 methoxamine 존재하의 전기 자극 반응은 영향을 받지 아니하였다. 3. $PGE_2$에 의한 억제작용은 Cd 중독군에서는 소실되었으나 꼬리 동맥에서 $PGE_2$의 억제효과는 Cd 중독으로 영향을 받지 아니하였다. 4. Cd 중독 꼬리 동맥에서 methoxamine 및 clonidine에 대한 수축반응은 최대 수축고가 현저히 낮아졌으나 $ED_{50}$치는 변화하지 아니하였다. 이상의 결과로 보아 Cd 중독시 정관에서 시냅스 전막 autoreceptor가 억제되어 교감 신경 흥분성이 증가함으로써 전기자극에 대한 반응이 항진되었다고 생각된다.