Abstract

FABRE, Bibiana Raquel et al. Screening of macroprolactin with polyethylene glycol: cut-off. Acta bioquím. clín. latinoam. [online]. 2006, vol.40, n.1, pp.77-81. ISSN 0325-2957.

The prolactin hormone (PRL) is a heterogeneous protein molecule found principally in three forms according to its size: monomeric (little PRL-23 kDa), dimeric form (big PRL-50 kDa) and macroprolactin (big-big PRL@ 150 - 170 kDa). The macroprolactin is formed, generally, by the association between the monomeric molecule and IgG immunoglobulins. The gel filtration chromatography (GFC) is considered the gold standard method for studying this macroprotein, but it is impractical and expensive. However, screening with precipitation with PEG 6000 is another method that is much more simple and inexpensive, but which needs to be previously validated by GFC. The objective of the authors was to establish a cut off to do the macroprolactin screening, using the precipitation with PEG and the DPC IRMA system. Twenty samples with serum levels of prolactin less than 18 ng/mL and 152 samples with serum prolactin levels greater than 30 ng/mL were analyzed. In patients with serum levels of PRL less than 18 ng/mL, the percentage of recovery of little PRL was 106 ± 11% (X ± 2 SD) and values lower than 50% were found in 23% of the samples with serum Prl greater than 30 ng/mL. In view of the percentage of recovery of PRL post precipitation with PEG, 6 samples with values of PRL lower than 50% of recovery post PEG and 3 greater than 50% were selected and chromatographed. In this work, a cut-off of 50% for the PEG method was found and GFC for all the samples between 40-60% of recovery is recommended.

Keywords : macroprolactin; screening; molecular heterogeneity.

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