Stereoselective inhibition of thromboxane-induced coronary vasoconstriction by 1,4-dihydropyridine calcium channel antagonists.
The biological activity of the (+)-S- and (-)-R-enantiomers of niguldipine, of the (-)-S- and (+)-R-enantiomers of felodipine and nitrendipine, and of rac-nisoldipine and rac-nimodipine was investigated in vitro and in vivo. Inhibition of coronary vasoconstriction due to the thromboxane A2 (TxA2)-mimetic U-46619 in guinea pig Langendorff hearts, displacement of (+)-[3H]isradipine from calcium channel binding sites of guinea pig skeletal muscle T-tubule membranes, and blood pressure reduction in spontaneously hypertensive rats were determined. The enantiomers were obtained by stereoselective synthesis. Cross-contamination was less than 0.5% for both S- and R-enantiomers of niguldipine and nitrendipine and less than 1% for those of felodipine. From the doses necessary for a 50% inhibition of coronary vasoconstriction, stereoselectivity ratios for (+)-(S)-/(-)-(R)-niguldipine, (-)-(S)-/(+)-(R)-felodipine, and (-)-(S)-/(+)-(R)-nitrendipine of 28, 13, and 7, respectively, were calculated. The potency ratio rac-nisoldipine/rac-nimodipine was 3.5. Ratios obtained from binding experiments and antihypertensive activity were (+)-(S)-/(-)-(R)-niguldipine = 45 and 35, (-)-(S)-/(+)-(R)-felodipine = 12 and 13, (-)-(S)-/(+)-(R)-nitrendipine = 8 and 8, and rac-nisoldipine/rac-nimodipine = 8 and 7, respectively. Highly significant correlations were found between the in vitro potency of the substances to prevent U-46619-induced coronary vasoconstriction and their affinity for calcium channel binding sites as well as their antihypertensive activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Eltze
M
M
Department of Pharmacology, Byk Gulden Pharmaceuticals, Konstanz, Federal Republic of Germany.
Boer
R
R
Sanders
K H
KH
Boss
H
H
Ulrich
W R
WR
Flockerzi
D
D
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000818:Animals; D001667:Binding, Competitive; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004095:Dihydropyridines / Q000378:metabolism / Q000494:pharmacology*; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D017275:Isradipine; D008297:Male; D009132:Muscles / Q000378:metabolism; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology*; D011725:Pyridines / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011918:Rats, Inbred SHR; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013928:Thromboxane A2 / Q000502:physiology*; D014316:Tritium; D014661:Vasoconstriction / Q000187:drug effects*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D011450:Prostaglandin Endoperoxides, Synthetic; D011725:Pyridines; D014316:Tritium; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D017275:Isradipine