Immunoreactive substance P and calcitonin-gene-related peptide (CGRP) in rat milk and in human milk and infant formulas.
This study examined the presence of substance P and calcitonin-gene-related peptide (CGRP) immunoreactivities in various milks and infant formulas. Rat milk was obtained from lactating dams between parturition and weaning (0, 2, 5, 10, 15, and 20 d postpartum). Samples of human milk were obtained from seven multiparous, nonsmoking white women, and newborn infant formulas were purchased from local stores. Substance P and CGRP were measured by competitive enzyme immunoassay using acetylcholinesterase-peptide conjugates as tracers. In rats, substance P and CGRP were below detectable concentrations in amniotic fluid from the last day of gestation. In contrast, in milk the concentrations of substance P and CGRP-like immunoreactivities were high on the first day of lactation (3.1 +/- 0.2 and 23.1 +/- 1.5 micrograms/L, respectively), then dropped after day 2 (1.6 +/- 0.7 and 7.5 +/- 0.4 microgram/L, respectively) and remained fairly constant until weaning. Significant concentrations of substance P and CGRP were found in human milk (129.2 +/- 27 ng/L and 4.5 +/- 0.7 microgram/L, respectively, at 15 wk), but substance P or CGRP could not be detected in any of the formulas tested. These data show that milk contains high concentrations of immunoreactive substance P and CGRP. In rats the absence of peptides in amniotic fluid suggests that there is a flood of peptides into the gastrointestinal tract of neonates when suckling is initiated. Significant concentrations of substance P and CGRP in human milk but not in infant formulas may therefore have physiologic implications for neonatal nutrition.
Ducroc
R
R
INSERM Unité 319, Université Paris 7, France.
Rubio
S
S
Garzon
B
B
Brunel-Riveau
B
B
Couraud
J Y
JY
D000653:Amniotic Fluid / Q000737:chemistry; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000737:chemistry*; D005260:Female; D005526:Food, Formulated / Q000032:analysis*; D006801:Humans; D007124:Immunoenzyme Techniques; D007225:Infant Food / Q000032:analysis*; D007231:Infant, Newborn; D008892:Milk / Q000737:chemistry*; D008895:Milk, Human / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D013373:Substance P / Q000737:chemistry*
D013373:Substance P; D015740:Calcitonin Gene-Related Peptide