Docosapentaenoic acid does not completely replace DHA in n-3 FA-deficient rats during early development

The reciprocal replacement of DHA by docosapentaenoic acid (DPAn-6) was studied in rats that consumed an n-3 FA-deficient or n-3 FA-adequate diet. Dams were fed the two experimental diets from weaning and throughout pregnancy and lactation. Their pups were then fed the respective diets after weaning. Cortex FA analysis was performed at various times (0, 5, 10, 20, 50, and 91 d) after birth to determine whether DPAn-6 completely replaced DHA in the n-3-deficient group. Cortical DHA levels were significantly lower (average 86%) in the n-3-deficient rats. DPAn-6 increased significantly in the n-3-deficient rats starting with a 6.5-fold increase at day 0 up to a 54-fold increase at day 91 compared with the n-3-adequate group. However, this significant increase did not completely replace the loss of DHA at postnatal days 5, 10, and 20 in which there was still an 11.5, 10.3, and 8.0% deficit in the sum of DHA and DPAn-6, respectively, in the n-3-deficient group. Once docosatetraenoic (DTA) and arachidonic acids (AA) were included in the sum (DHA + DPAn-6 + DTA + AA), the levels between the two groups were similar. These results suggest that not only DPAn-6 but also other n-6 FA, including DTA and AA, replace DHA in n-3-deficient rats. The lack of total 22-carbon (22C) FA in the brain during the rapid membrane biogenesis that occurs during early development could be a factor in the nervous system functional deficits associated with n-3 FA deficiency.