Motilin in human milk and its elevated plasma concentration in lactating women

The aims of this study were to investigate whether: (i) lactating women had an elevated plasma level of motilin; (ii) there was a correlation between the plasma motilin level and the motilin level in breast milk in lactating women; and (iii) there was a difference in motilin levels between the colostrum and mature human milk in a controlled postprandial state.

Twenty control women and 18 lactating women were enrolled in this study. All samples were drawn in a controlled postprandial state. The concentration of motilin was measured using radioimmunoassay.

The plasma motilin level in lactating women was 434 +/- 180 pmol/L on the fifth day after delivery and 450 +/- 204 pmol/L on the 42nd day after delivery (P > 0.05). Both of these values were significantly higher than those in the control women (231 +/- 48 pmol/L, P < 0.05). The motilin level in human milk in the controlled postprandial state was 161 +/- 56 pmol/L on the fifth day and 154 +/- 60 pmol/L on the 42nd day after parturition (P = 0.7). Although there was motilin in the breast milk and an elevated plasma level of motilin in the lactating women, there was no correlation in motilin level between the blood and the breast milk.

Motilin is elevated in the blood of lactating women and human milk contains motilin. These elevated levels of motilin sustain for a period of at least 6 weeks. Further studies are necessary to assess whether motilin is involved in the development of gastrointestinal motility in the early stage of life in infancy.