Effect of cross-fostering rats at birth on the normal supply of essential fatty acids during protein deficiency.

The effect of protein deficiency on the activity of delta 6 desaturase in the mother during lactation was determined in the liver microsomal fraction and the fatty acid composition of milk lipids from the analyzed stomach contents. The activity of delta 6 desaturase was profoundly affected by protein deprivation during pregnancy and only reached the values of controls at about 10 days after parturition. This fact did not affect the fatty acid pattern of milk lipids and no significant differences in the contents of arachidonic acid were detected between the two groups. Nevertheless, protein deficiency apparently affected milk production. The effects of protein deprivation on the supply of polyenoic acids of cross-fostering rats at birth from protein-deficient to protein-sufficient diets and vice versa, and rats maintained during pregnancy and lactation on a low protein or control diet were examined. The fatty acid pattern of liver phospholipids of the four groups under study was determined and used as a biochemical parameter for evaluating polyenoic acid status. Protein deficiency markedly affected the fatty acid pattern of liver phospholipids. A significant decrease of both arachidonic and docosahexaenoic acids was observed. This fatty acid pattern was reversed when protein-deficient animals were placed on the control diet at birth. On the other hand, the fatty acid composition of controls was negatively affected by cross-fostering to a deficient diet. The findings from the present experiment provide evidence that the negative effect of protein malnutrition appears to be promoted at least in part, by the effect of protein depletion on the supply of polyenoic acids for normal development and metabolic adaptations.