Plasma, phytanic acid content

Phytanic acid content of totai plasma lipid extract... 

Plasma lipids were extracted by the method of Folch et alP- after the addition of an internal standard. Standards of phytanic acid were similarly treated. Constituent fatty acids were then converted to their methyl esters and analysed by gas-liquid chromatography. The phytanic acid content was calculated by comparison of the ratio of the peak heights of phytanate to internal standard for the test with those for the standard. Phytanic acid was also calculated as a percentage of all fatty acids from C,4 to Cjo by comparison of peak areas calculated from the product of peak height and retention time. The results are shown in Table 8.1 where it can be seen that phytanic acid accounts for 50% of the total plasma fatty acids. 

Phytanic acid content of plasma lipid subfractions... 

A sheet of skin from one thigh of the patient was obtained by keratotome biopsy (Castroviejo keratotome set at 0.4 mm). Epidermis was prepared from this by heating in saline at 60 °C for 4 minutes. After freeze-drying and desiccation, the samples were weighed and analysed as described for the plasma. Samples of skin from two normal subjects were prepared and analysed in an identical way for comparison. The percentage of phytanic acid in the epidermal lipid subfractions is shown in Table 8.3. Large amounts of phytanic acid were found in all subfractions. Each subfraction was then analysed for individual fatty acid content and the results are shown in Table 8.4. 

The biochemical analyses have revealed considerable quantities of free and esterified phytanic acid in plasma and epidermis. In the latter, large amounts of phytanic acid was found in all lipid subfractions. Analysis of the phospholipid subfraction in this patient and of two normal controls (Table 8.4) showed a striking reduction in linoleic acid (18 2) content from a mean of 36.6% in the controls to 5.4% in the patient with Refsum s disease. A similar, though less marked reduction was observed in the arachidonic acid (20 4 o>6) levels in the epidermal phospholipid subfraction in the patient with Refsum s disease. Both linoleic acid and arachidonic acid are known to be essential fatty acids in man and animals a deficiency producing an ichthyosis-like scaling dermatosis. 

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