@article {1172251, title = {Charge properties of human pituitary and amniotic fluid prolactins}, journal = {Endocr Res Commun}, volume = {2}, number = {6-7}, year = {1975}, month = {1975}, pages = {379-402}, abstract = {The apparent isoelectric points (pI) in isoelectric focusing (IF) of human pituitary and amniotic fluid prolactin (hPRL), both non-iodinated and iodinated, were determined. Unresolved mixtures of pituitary hPRL isohormones E and F, and of at least five isohormones found in amniotic fluid, and plasma hPRL exhibit an average pI value of 6.5 - 6.7. Transient state pH values observed or previously reported for hPRL components range from pH 5.9 to 6.8 after correction to standard conditions. At pH 8.1, the major isohormone, hPRL-F, carriers a charge of 2.2 net protons per molecule. The net charge differences among isohormones E, F and G are compatible with acquisition or loss of single charged groups per 20,000 molecular weight. This net charge is similar to that of the least prolactin-bioactive major isohormone of human growth hormone (hGH-B), while the hGH with a bioactivity comparable to that of hPRL exhibits a net charge of 3.4 valence units. The "large" isohormones J and H increased net charges, by a factor of 2-3, in direct proportion to their size increments.}, keywords = {Amniotic Fluid, Female, Humans, Hydrogen-Ion Concentration, Isoelectric Focusing, Lactation, Pituitary Gland, Pregnancy, Prolactin, Radioimmunoassay}, issn = {0093-6391}, author = {Rogol, A D and Ben-David, M and Sheats, R and Rodbard, D and Chrambach, A} }