title: Endogenous digitalis-like factors in human milk.
abstract: We measured the concentration of endogenous digitalis-like factors (EDLFs) in milk or colostrum of women during nursing on different days after delivery. EDLF concentrations were assayed by a solid-phase RIA involving antidigoxin antibodies and by a radioreceptor assay (RRA) involving human placenta Na+/K(+)-ATPase. The mean (SD) EDLF concentrations as measured by RIA were 35.6 (19.4) ng of digoxin equivalents per liter in milk samples (n = 37) and 61.3 (12.5) ng/L in colostrum samples (n = 5); the mean EDLF concentration as measured by RRA in milk samples (n = 11) was 573 (717) ng/L (range 0-2098). EDLF concentration in milk is greater than circulating concentrations in healthy adults but is comparable with serum concentration in the third trimester of pregnancy. In milk and serum samples (n = 8) collected at the same time, heating and (or) extracting with Sep-Pak C18 cartridges before the RIA produced significantly different EDLF values from those in untreated serum (P less than 0.001) and milk (P = 0.035). EDLF in milk appeared to be not bound or weakly bound to milk protein, as indicated by the fact that boiling did not increase the digoxin-like immunoreactivity.
authors.affiliation: Istituto di Fisiologia Clinica del CNR, Pisa, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Clerico
authors.forename: A
authors.initials: A
authors.lastname: Paci
authors.forename: M G
authors.initials: MG
authors.lastname: Del Chicca
authors.forename: P
authors.initials: P
authors.lastname: Biver
authors.forename: O
authors.initials: O
authors.lastname: Giampietro
mesh_terms: D001798:Blood Proteins / Q000032:analysis*; D002298:Cardenolides; D003126:Colostrum / Q000737:chemistry; D004077:Digoxin; D005260:Female; D006801:Humans; D007774:Lactation; D008895:Milk, Human / Q000737:chemistry*; D010920:Placenta / Q000201:enzymology; D011863:Radioimmunoassay; D011869:Radioligand Assay; D012016:Reference Values; D012503:Saponins; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D002298:Cardenolides; D012503:Saponins; C034504:digoxin-like factors; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase