Abstract
To prevent first pass metabolism of dopamine (DA) in the intestinal absorption process, DA-dipeptide derivatives, in which the amino group of DA was protected by dipeptides containing Phe and Pro, were synthesized, and the hydrolysis of these compounds by rat liver, jejunum and ileum homogenates, 10, 000 g supernatant and precipitate (ppt), were investigated. Significant differences were not found between the DA-releasing rates from Phe-Phe-DA and Pro-Phe-DA by the homogenates and that from Phe-DA, because Phe-Phe and Pro-Phe were hydrolyzed rapidly by the homogenates. On the other hand, the DA-releasing rates from Phe-Pro-DA and Pro-Pro-DA by the homogenates ppt were much larger than that from Pro-DA, suggesting that the existence of Phe and Pro at the P2 site in the DA-dipeptide derivatives promote the DA-releasing rates from these derivatives. The results indicate the feasibility that the dipeptides containing Pro at the P1 site may be useful promoieties for the control of the DA-releasing rate from the DA-dipeptide derivatives.
