It has been shown from the apparent first-order urinary excretion studies of D-( -)-mandelic acid and certain of its homologs, DL-tropic acid, D-( -)-4-hydroxy-4-phenylbutanoic acid, DLphenyllactic acid, and D-( -)-benzyllactic acid, that the biological half-lives of the hoinologs are significantly shorter than that of D-( -)-mandelic acid in rats. Since these compounds, which differ from each other in their content of methylene groups around the carboxyl group, exhibit negligible metabolism and protein binding, low pKa values (3.3-4.7), and low lipid solubility at the physiological pH, and are primarily recovered in the urine in the intact form, they are utilized in these studies as model compounds to study the effect of hydrophobic group(s) on the rate of secretion. These compounds are shown to exert a mutual inhibitory effect on their renal tubular secretion, indicating a common "carrier" mechanism for their secretion. The utilization of these compounds indicated that the addition of methylene group(s) in the vicinity of the carboxyl group of the mandelic acid molecule increased its affinity for the carrier molecules of the renal tubular secretion system in rats.
Keyphrases [? D-( -)-Mandelic acid and homologs-mutual inhibition of urinary excretion 0 Urinary excretion-D-( -)-mandelic acid and homologs 0 Excretion rates, apparent-D-( -1mandelic acid and homologs 0 ORD-identity 0 Polarimetryidentity 0 GLC-analysis