Eiichi Sakurai

In vivo microdialysis measurement of histamine in rat blood effects of compound 48/80 and histamine receptor antagonists

An in vivo microdialysis method combined with a highly sensitive HPLC method which was developed for the analysis of the mediators in the CNS has been applied to assay histamine concentrations in the blood. The technique was used to study the effects of compound 48/80 and histamine receptor antagonists on histamine release in the blood of rats. The mean basal level of histamine in the blood measured by in vivo microdialysis was 177.8 +/- 11.1 pmol/mL. This level was not affected significantly by intraperitoneal (i.p.) injection of saline, and remained at the constant level for at least 8 hr after injection of saline. After i.p. injection of histamine (0.5 mg/kg), histamine was quickly detected in the blood of the jugular vein. Moreover, because the recovered histamine in the dialysate is directly proportional to the free fraction in the blood, the in vivo microdialysis method of blood is a reliable method of examining histamine release into the blood. In our experiments, the histamine level in dialysates from rat jugular vein was markedly increased by compound 48/80 (2.0 mg/kg, i.p.), demonstrating the histamine release into the blood from mast cells. However, there was no increase in histamine concentration after an i.p. injection of histamine receptor antagonists, such as pyrilamine (2.0 mg/kg), d-chlorpheniramine (2.0 mg/kg), cimetidine (10 mg/kg), or thioperamide (10 mg/kg). Thus, the present results suggested that these histamine receptor antagonists might not have an influence on histamine release into the blood.

[Determination of disaccharidase activity in rat serum, bile, urine and various tissues by high-performance liquid chromatography with differential refractometric detection].

A simple and high sensitive method for the determination of disaccharidase in various biological samples of rats by high-performance liquid chromatography (HPLC) with a differential refractometric detection was developed. This method, as compared with the Dahlqvist method, has the following advantages; 1) There is no necessity for the elimination of biological components which have an influence on the determination of glucose. 2) Only a little enzyme sample is used. 3) The detection limit of a reaction product, glucose, by the HPLC method is about 10 times higher than that by the Dahlqvist method. 4) The maltase activity in the small intestinal mucosa estimated by HPLC method is positively correlated with that estimated by the Dahlqvist method (r = 0.9661, p less than 0.001, n = 8). 5) This method developed in the present study is applicable to not only the small intestinal mucosa, but also serum, bile, urine and various tissues.

Effects of Various Cathartics and Deoxycholic Acid on the Disposition of Endogenous Bile Acids in the Bile, Portal Blood and Feces of Rats

The effects of various cathartics (magnesium sulfate, mannitol, dioctyl sodium sulfosuccinate (DSS), castor oil and pilocarpine) and deoxycholic acid (DCA) on the disposition of endogenous bile acids in the bile, portal blood and feces of rats were investigated. The biliary bile acids of free type increased significantly after the oral administration of cathartics except for DSS. The amounts of glyco- and tauro-conjugated bile acids showed different patterns after the oral administration of various cathartics. However, the proportion of DCA significantly increased in the case of diarrhea induced by cathartics, and the proportion of cholic acid (CA) conversely decreased compared with the control. Thus, it was suggested that unconjugated bile acids eliminated into the intestinal lumen and DCA formed from CA participate in the occurrence of diarrhea after oral administration of various cathartics. Moreover, the ratio of glycine- to taurine-conjugated bile acid of rat bile increased when diarrhea was induced by various cathartics. Thus result suggested that the reabsorption of tauro-conjugated bile acids is decreased, or that the reabsorption of glyco-conjugated bile is increased in diarrhea.On the other hand, DCA caused diarrhea in rats. The occurrence of diarrhea was concentrated within 20 to 24 h after the oral administration of DCA. Since biliary unconjugated and glyco-conjugated bile acids were increased at 24 h after DCA treatment, whereas glyco-conjugated bile acids were decreased in the portal blood, it is conceivable that deconjugation is accelerated by changes in the activity of intestinal bacteria and in the liver after DCA treatment. Active transport of tauro-conjugated bile acids from the end of the ileum may have been impaired, because the absorption of tauro-conjugated bile acids was inhibited from 1 h after the administration of DCA.