Ieda H, Naruse S, Kitagawa M, Ishiguro H, Hayakawa T
Department of Internal Medicine II, Nagoya University School of Medicine, Japan.
Regul Pept. 1999 Feb 5;79(2-3):165-71. doi: 10.1016/s0167-0115(98)00162-1.
The effects of rat guanylin, human guanylin, human uroguanylin and STa on net fluid and electrolyte transport in the closed jejunal loop were compared in anesthetized rats. STa administered into the lumen caused a concentration-dependent (10(-8) to 10(-6) M) inhibition of net fluid and NaCl absorption in the jejunal loop. Uroguanylin had a similar but weaker effect than STa. Both rat and human guanylin inhibited fluid and NaCl absorption only at 10(-6) M. Their order of potency was STa > human uroguanylin > rat guanylin = human guanylin. Changing the luminal pH from 5 to 8 failed to affect the action of guanylin on fluid absorption. Both STa and uroguanylin, but not guanylin, increased the luminal pH by stimulating bicarbonate secretion. Pretreatment of the jejunal loop with guanylin (10(-6) M) 5 min before the instillation of STa (10(-7) M) significantly reduced the inhibitory effect of STa on fluid absorption. It is concluded that guanylin and uroguanylin administered into the rat jejunal lumen have an STa-like action on fluid and electrolyte transport. Guanylin may act as an endogenous antagonist of STa in the rat jejunum and prevent excessive fluid loss by STa.
在麻醉大鼠中比较了大鼠鸟苷素、人鸟苷素、人尿鸟苷素和STa对封闭空肠袢中液体和电解质净转运的影响。向肠腔内注入STa会导致空肠袢中液体和NaCl净吸收呈浓度依赖性（10⁻⁸至10⁻⁶M）抑制。尿鸟苷素具有与STa相似但较弱的作用。大鼠和人鸟苷素仅在10⁻⁶M时抑制液体和NaCl吸收。它们的效力顺序为STa＞人尿鸟苷素＞大鼠鸟苷素 = 人鸟苷素。将肠腔pH从5改变为8未能影响鸟苷素对液体吸收的作用。STa和尿鸟苷素均可通过刺激碳酸氢盐分泌来提高肠腔pH，但鸟苷素无此作用。在注入STa（10⁻⁷M）前5分钟用鸟苷素（10⁻⁶M）预处理空肠袢，可显著降低STa对液体吸收的抑制作用。得出的结论是，向大鼠空肠腔内注入鸟苷素和尿鸟苷素对液体和电解质转运具有类似STa的作用。在大鼠空肠中，鸟苷素可能作为STa的内源性拮抗剂，防止因STa导致的过多液体流失。
