Hydrocarbons disposition, lipid content, and fatty acid composition in trout after long-term dietary exposure to n-alkanes.

Uptake, distribution, and storage of n-alkanes was studied in rainbow trout receiving a diet containing 1% normal paraffins in the C13-C22 range. After 3 months, the concentration of hydrocarbons deposited in the whole body reached a steady equilibrium value in the range 700-900 ppm. The most pronounced deposition occurred in the adipose tissue. The n-alkane pattern in the whole body exhibited a profile different from that of the alkane mixture ingested. The alkanes around C20 were not retained to any great extent, but as the chain length decreased, the relative amount stored increased. In the liver a marked predominance of even-carbon chain length was observed while in whole fish and in other organs such a phenomenon did not occur. After 5 months, total lipids in the carcass were significantly lower in the test group than in the control group. At the end of the accumulation period, a significant enhancement in the proportion of odd- and even-chain saturated fatty acids from C14:0 to C18:0 was noted in carcasses of hydrocarbon-fed fish. Myristic, pentadecanoic, and heptadecanoic acids were also significantly more abundant in the liver and adipose tissue of contaminated fish. This increase is attributed to the terminal oxidation of the predominant n-alkanes in the diet into the corresponding fatty acids. During the depuration period, one-half of the trout in each group were fed a hydrocarbon-free diet, while the others were starved. After 2 months, both starved and fed trout had lost approximately 50% of the amount of total n-alkanes stored. The n-alkanes longer than C16 were well retained, while short-chain alkane concentration decreased rapidly.