EFFECT OF NICKEL DEFICIENCY ON FATTY-ACID COMPOSITION OF MILK AND ADIPOSE-TISSUE OF RATS

The present investigation was attempted to examine the effect of nicke l deficiency on fat content and fatty acid composition of milk resulti ng from 2 successive lactation cycles from rat dams and fatty acid com position of adipose tissue from the 51-day-old second offspring. In th is experiment weaned female SPF Sprague-Dawley rats were divided into 2 groups of 12 animals each and were fed 2 diets differing in nickel c ontent, containing 13 mu g/kg nickel (nickel-deficient diet) or, respe ctively, 1 mg/kg nickel (nickel-adequate diet). In order to bring out signs of nickel deficiency rats were mated 2 times to produce the firs t and second offspring. During both lactation cycles at day 10 milk wa s determined for its fat content and fatty acid composition. Fatty aci d composition of adipose tissue was determined in the pups from the se cond offspring, which were raised for another 4 weeks subsequent to th e weaning period with a nickel-deficient or a nickel-adequate diet. Tr iacylglycerol content of milk from the first lactation period was abou t 22% and not altered due to nickel deficiency. During the second lact ation cycle milk from nickel-depleted dams had a tendentiously higher triacylglycerol content by about 25% than the nickel-adequate rats. Ni ckel deficiency had only a slight influence on fatty acid composition both in milk of dams and adipose tissue of 51-day-old offspring, altho ugh the pups had in contrast to the dams essentially pronounced nickel deficiency symptoms. The most marked variations in milk provoked by n ickel deficiency was a higher proportion of medium chain fatty acids ( MCFA) from both lactation cycles, whereas this effect was more pronoun ced in milk from the second lactation cycle than from the first. On cl oser examination the increase in MCFA was at the expense of 16:0. Conv ersely, the mean chain length of milk fatty acids was not influenced b y dietary nickel. It was assumed that the increase in milk fat content and MC:FA due to nickel deficiency results from a decrease in milk yi eld, regulated by prolactin. Fatty acid composition of adipose tissue from second offspring was also slightly altered by nickel deficiency. Adipose tissue from nickel-depleted pups had higher proportions of 10: 0, 14:0, and 18:0 than that of control animals, whereas the proportion s of 14:1 and 16:1 were lower. Total SFA and MUFA levels did not essen tially differ within the groups. The proportion of total PUFA in adipo se tissue was significantly lower due to nickel-deficiency, and this r eduction was mainly due to a fall in 18:2 (n-6) and 18:3 (n-3). It was suggested that the altered fatty acid composition in adipose tissue p roduced by nickel deficiency was due to altered incorporation or utili zing of fatty acids.