P0117 PP BLOOD PLASMA ENKEPHALINASE ACTIVITY OF BREASTFEEDING AND BOTTLE-FEEDING INFANTS: INTERRELATIONSHIP WITH TEMPERAMENT

Abstract

Introduction: Breast milk is an unique product in providing optimal infant’s development. Breastfeeding was reported to provide advantage for the development of intelligence and endocrine system maturation in infants. On the other hand, these processes depend on child personality and proceed under regulation by neurochemical systems. The influence of breastfeeding and bottle-feeding on the main peptidergic regulatory systems, endogenous opioid system, for example, in early postnatal period is not studied. The aim of our research was to evaluate enzymatic degradation of opioid peptide leuenkephalin in blood plasma of breastfed and bottle-fed infants and to estimated its possible interrelationship with children personality. Methods: 93 healthy infants (50 boys and 43 girls) at the age of 1 to 12 months were entered into the investigation. 33 (36%) of them were breastfed and 60 (64%) bottle-fed. The level of psychomotor development was estimated by means of the quantitative scale of mental and motor development for infants [Zhurba, Mastukova, 1981]. Temperament was studied by means of EITQ and ITQ questionnaires [W.B.Carey et al, 1986]. Enkephalinase activity in plasma was estimated in vitro by the rate of 3H-leu-enkephalin hydrolysis at low substrate concentration (half-life time of leu-enkephalin, t1/2). [Sokolov et al., 2000]. Results: It was found that t1/2 of leu-enkephaline was significantly less in infants than in adults. Between infants with normal psychomotor development t1/2 of leu-enkephaline was higher in girls comparing to boys (2.51+ 0.08 vs 2.26+ 0.06 min respectively, p<0.01) and higher in bottle-fed infants comparing to breastfed (2.15*0.07 vs 2.48*0.06 min respectively, p<0.001). In infants with delayed psychomotor development these differences were not detected. Nevertheless, there was no relationship between t1/2 and infants psychomotor development. We also demonstrated correlation of t1/2 with such characteristics of infant temperament as Activity, Approach, Threshold (p<0.05). We did not find any significant correlation between the temperament characteristics and the level of mental and motor development of infants. Conclusion: Our data showed that blood plasma enkephalinase activity is different in breastfed and bottle-fed infants. Probably, it might be one of mechanism of feeding type influence on opioid system in infants of first year of age. For the first time we demonstrated the correlation between enkephalinase activity and some characteristics of child temperament, but not psychomotor development.