A series of in vivo experiments is described in which [1-13C]
phytanic acid was given as an oral substrate to a healthy subject and two patients showing an impairment in
phytanic acid degradation, one with
Refsum's disease and one with
chondrodysplasia punctata. After intake of the substrate by the control in a dose of 20 mg/kg
body weight, the production of 13CO2 was measured in exhaled breath air and the concomitant formation of labeled
2-hydroxyphytanic acid and of
pristanic acid was demonstrated by plasma analysis. After application of a substrate dose of 1 mg/kg
body weight to the control, no substantial amounts of 13CO2 were measured, whereas time-dependent analysis of labeled
2-hydroxyphytanic acid in plasma yielded a concentration curve superimposed upon the baseline value (0.2 mumol/L) of the unlabeled substance.
Phytanic acid accumulated in plasma from the
Refsum's disease patient [649 mumol/L, controls > 1 y (n = 100): < 10 mumol/L], whereas the
pristanic acid concentration was within the control range [1.4 mumol/L, controls > 1 y (n = 100): < 3 mumol/L]. Low amounts of
2-hydroxyphytanic acid were found normally present [0.04 mumol/L, controls > 1 y (n = 11): < 0.2 mumol/L], and formation of labeled
2-hydroxyphytanic acid could not be demonstrated after ingestion of [1-13C]
phytanic acid in a dose of 1 mg/kg
body weight. In addition to
phytanic acid accumulation (232 mumol/L), the
chondrodysplasia punctata patient showed an elevated
2-hydroxyphytanic acid plasma concentration (0.4 mumol/L), whereas the plasma
pristanic acid level was in the control range (0.7 mumol/L).(ABSTRACT TRUNCATED AT 250 WORDS)