Human prolactin in plasma, amniotic fluid and pituitary: identity and characterization by criteria of electrophoresis and isoelectric focusing in polyacrylamide gel.

Abstract

Human prolactins (hPRL) from the following sources: plasma of normal lactating women, plasma of a male patient with chromophobe adenoma and galactorrhea, amniotic fluid and a purified pituitary preparation, are indistinguishable on the basis of molecular size, net charge or apparent isoelectric point. In polyacrylamide gel electrophoresis (PAGE) under 3 sets of conditions (at pH 10.2 and 7.8, 0 C, or at pH 9.5, 25 C), hPRL from plasma and amniotic fluid was found to be a single, biologically and immunologically active protein distinct from human growth hormone (hGH) on the basis of its free mobility and net charge which, under all three sets of conditions, is less than that of the least charged major component of hGH. This result was substantiated by bioassay under a single set of conditions. However, the molecular size of hPRL is not significantly different from that of hGH. The apparent isoelectric point of hPRL is 6.5.