Structurally modified fatty acids: clinical potential as tracers of metabolism

Recently 15-p-iodophenyl-beta-methyl-pentadecanoic acid (BMPPA) was proposed for use in myocardial scintigraphy, as a possible probe of metabolic processes other than beta-oxidation. In 19 patients (CAD/15, St.p. Mi/7; control 4) myocardial scintigraphy was carried out after i.v. I-123-BMPPA (2-4 mCi). Data were collected (LAO 45 degrees/14; anterior/5) for 100 min in the fasted patients. Organ to background (BG) ratios were calculated for the heart (H) and liver (L), and the elimination (E) behaviour was analyzed from BG (vena cava region) corrected time activity curves. In 10 patients plasma and urine were examined. By CHCl3/MeOH extraction of plasma samples (90 min after injection), both in water and in organic medium soluble catabolites were found. TLC fractionation showed that those were co-migrating, compared to standards, with bencoic acid, BMPPA and triglycerides. In the urine (0-2 h after injection, 4.1% dose) hippuric acid was found. The mean t-max of BMPPA occurred at 15 min in the heart and at 9 min in the liver (P less than 0.01), with H/BG and L/BG ratios of 1.8 and 2.1, respectively. The elimination of BMPPA was slower from the heart than from the liver (P less than 0.01). It was biexponential from the liver in all cases (means: t/2 I, 11.4 min; t/2 II, 92 min; t/2 I uncor., 38 min) with the size of phase I smaller than that of phase II (means: I/II, 0.57). From the heart BMPPA turnover was biexponential in 11 patients (means: t/2 I, 13.8 min; t/2 II, 187 min; t/2 I uncor., 65 min; I/II, 0.34), but monoexponential in 8 (means: t/2, 218 min).(ABSTRACT TRUNCATED AT 250 WORDS)