Small Intestinal Absorption of Methylene Blue in Rats, Guinea Pigs and Rabbits

Abstract

Small intestinal tracts of rats, guinea pigs, and rabbits were recirculated in situ with methylene blue (MB), and the average absorption ratios in 120 min were 54, 36, and 47%, respectively. Therefore the great species difference in MB absorption capacity was not observed in these three experimental animals. At the same time 7.7, 46, and 30% of the dose were found as leucomethylene blue (LMB) besides the unchanged methylene blue in the perfusate for rats, guinea pigs, and rabbits, respectively. In situ perfusion experiments revealed that the concentration of total MB (MB+LMB) in bile at 150 min was five times greater than the initial MB concentration in the perfusate, and that 8 and 12.8% of the total MB absorbed were excreted in bile and urine, respectively. The total excreted MB contained 96.8% LMB in bile, and 94.1% in urine. MB was reduced to LMB under anaerobic condition by incubation with everted sacs of the small intestines of guinea pigs and rats, and the reduction was not reversible in the incubation medium under the same condition in the sense of net reaction. In vitro absorption experiment employing the everted sacs of the small intestines of rats, guinea pigs, and rabbits suggested that LMB besides MB would be also absorbable from the small intestines of the experimental animals in situ.