Bioactivity of prolactin isoforms
No Thumbnail Available
Date
1999
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
To assess whether plasma prolactin (PRL) characteristics relate to lactogenesis and absence or presence of menstrual cycles, we measured bioactive PRL (BIO;PRL) using the Nb2 assay, immunoreactive PRL (TR-PRL) by radioimmunoassay, calculated equations describing the BIO-PRL-IR-PRL relationship and separated charged PIiL isoforms (by chromatofocusing) in five amenorrhoeic and five cycling nursing women at 6 months postpartum and in 10 cycling non-nursing women, Plasma samples were drawn before and 30 min after a suckling episode at 0800, 1600 and 2400 h in nursing women and at the same hours ih non-nursing women. BIO-PRL and IR-PRL concentrations were highest in amenorrhoeic nursing women, intermediate in cycling nursing women and lowest in cycling non-nursing women. The BIO-PRL-IR-PRL relationship shows that a given amount of IR-PRL corresponds to equivalent amounts of BIO-PRL in cycling nursing and cycling nonnursing women, and to a larger extent in amenorrhoeic nursing women. IR-PRL was present In plasma as several charge isoforms, Bioactive isoforms eluting at PH 6.0-5.1 were found in amenorrhoeic and cycling nursing women, reaching similar concentrations after suckling. Bioactive isoforms eluting at pH 7.0-6.1 were found only in amenorrhoeic nursing women. We speculate that isoforms eluting at pH 6.0-5.1 may play a role in lactation and isoforms eluting at pH 7.0-6.1, in lactational amenorrhoea.
Description
Keywords
lactation, lactational amenorrhoea, prolactin isoforms