Endogenous digitalis-like factors in human milk.
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.
Clerico
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A
Istituto di Fisiologia Clinica del CNR, Pisa, Italy.
Paci
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A
Del Chicca
M G
MG
Biver
P
P
Giampietro
O
O
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
D001798:Blood Proteins; D002298:Cardenolides; D012503:Saponins; C034504:digoxin-like factors; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase