Phosphodiesterase inhibition and lipolytic action of the stereoisomers of trimetoquinol

The isomers and racemate of trimetoquinol [TMQ; 6 7 dihydroxy 1 (3',4',5' trimethoxybenzyl) 1,2,3,4 tetrahydroisoquinoline] as well as N (3',4',5' trimethoxyphenethyl) dopamine were all shown to be effective at promoting glycerol release from rat epididymal fat tissue. The rank order of potency observed for these compounds was (-) TMQ ≥ (±) TMQ >> (+) TMQ = N (3 trimethoxyphenethyl) dopamine. (±) TMQ and (-) TMQ were the only agents capable of producing a maximal lipolytic response. None of the compounds tested were able to exhibit significant c AMP phosphodiesterase inhibition. This study is the first report which shows that the β adrenoceptor activity of the isomers of TMQ does not correlate with an inhibition of c AMP phosphodiesterase. An alternate mechanism of action for these compounds is proposed.