부산대학교 도서관

In an effort to investigate the enhancement effect of lanthanide ions (Ln.sup.3+) on the absorption of larger molecules from the pulmonary pathway, insulin (mol. wt.=5730) was chosen as a model peptide. The absorption of insulin preadministered or coadministered with Ln.sup.3+ from the lung was investigated by means of an in situ pulmonary absorption experiment. The enhancement absorption of insulin by Ln.sup.3+ ions was evaluated by calculating the various bioavailabilities (Fr) of insulin from pulmonary absorption. Moreover, the temporal change of Gd content in serum was also investigated. Results showed that the promoting effect of Ln.sup.3+ on the bioavailability of insulin is closely related to its species, concentration, and delivery order. The effect of the median Ln.sup.3+ series was remarkably greater than that of light and heavy Ln.sup.3+. The anionic form of Gadolinium (Fr=68.4%) seemed to be more effective compared with its cationic form (Fr=59.5%). Coadministration of Gd.sup.3+ with insulin (Fr=80.1%) was the most effective in increasing insulin absorption from the lung. Gd.sup.3+ was rapidly absorbed and metabolized to a normal level after 4 h. It was suggested that lanthanides in a very low concentration might become potent absorption enhancers to improve absorption of larger molecules via the pulmonary pathway.