[Effects of fudosteine, a new cysteine derivative, on airway secretion in rabbits and rats].

We examined the effects of fudosteine [(-)-(R)-2-amino-3-(3-hydroxypropylthio) propionic acid], a new cysteine derivative, on airway secretion in rabbits and rats. Indirect measurement of airway secretion in rabbits, which was expressed by the amount of dye excreted into the respiratory tract, was carried out according to the Sakuno's method, with some modifications. Fudosteine (500 mg/kg, p.o.) significantly increased the amount of dye excreted into the respiratory tract. As a direct method of measurement of airway secretion, the modified Perry and Boyd's method was used to collect respiratory tract fluid (RTF) in rabbits. Fudosteine (500 mg/kg, p.o.) significantly augmented the output volume of RTF, but there was no difference from the control in protein and phosphatidylcholine (PC) contents into RTF. On the other hand, fudosteine increased chloride ion concentration in broncho-alveolar lavage of rats. Fudosteine did not stimulate PC secretion in a primary culture of rat type II pneumocytes, and it did not have a mucolytic effect against gastric mucin in vitro. From the results described above, it was concluded that fudosteine may be a new cysteine derivative which offers a serous secretion.