Correlation between hydrophobicity of N-alkylxanthine derivatives and their biological activities on guinea-pig isolated tracheal smooth muscle.
Cyclic (c) AMP phosphodiesterase (PDE) inhibitory activities of N-alkylxanthine derivatives (3-methyl-,3-ethyl-,3-propyl-,3-butyl-,1,3-dimethyl-,1-methyl-3-ethyl-,1-methyl - 3-propyl- and 1-methyl-3-butyl xanthines) and their relaxant effects on carbachol-induced contraction and on resting tone guinea-pig isolated tracheal smooth muscle have been investigated. The PDE inhibition constant (Ki) and the concentration producing 50% tracheal smooth muscle relaxation in-vitro (EC50) were determined. Significant correlations between the -log Ki values and the -log EC50 values on the carbachol-induced contraction or on the resting tone were found (r = 0.902 and 0.892). The apparent partition coefficient (P) between n-octanol and pH 7.4 phosphate-buffered saline (PBS) was measured as an index of hydrophobicity of the xanthine derivatives. There were significant correlations between log P and both -log EC50 values and between the log P and -log Ki values. These findings suggest that the cAMP PDE inhibitory activity of N-alkylxanthine derivatives contributes to the mechanism of bronchodilatory action, and that an increase in hydrophobicity of the xanthine molecule enhances the biological activity.
Miyamoto
K
K
Research Laboratory for Development of Medicine, School of Pharmacy, Hokuriku University, Kanazawa, Japan.
Takagi
K
K
Sakai
R
R
Wakusawa
S
S
Koshiura
R
R
Nadai
M
M
Apichartpichean
R
R
Hasegawa
T
T
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000818:Animals; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D012995:Solubility; D014132:Trachea / Q000187:drug effects; D014970:Xanthines / Q000032:analysis / Q000494:pharmacology*
D014970:Xanthines; D015105:3',5'-Cyclic-AMP Phosphodiesterases