ヒトProlactin (PRL) のHeterogeneityに関する研究

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概要

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• The heterogeneity of human PRL has been demonstrated by gel filtration and subsequent radioimmunoassay of each fraction. Three distinct froms of PRL, peak I (void volume), II and III (monomeric) PRL, were identified after fractionation of serum of a case with PRL secreting pituitary tumor. To further study variations and physiological significance of these different froms of PRL, we observed fractionation patterns of serum PRL before and after TRH administration in normal subjects and in patients with idiopathic galactorrea. In normal subjects, TRH markedly increased monomeric PRL with a resultant relative increase in percentage of peak III or monomeric PRL, whereas peak II PRL increased to a lesser extent and change of peak I PRL was not satistically significant. In idiopathic galactorrhea, the distribution of the three forms of PRL was similar to that of a TRH-stimulated state in normal subjects. TRH administration did not alter the basal pattern and increase in whole serum PRL by TRH stimulation was much less than in normal subjects. <BR>To examine the possibility of conversion of monomeric to larger molecular forms in peripheral circulation, purified <SUP>125</SUP> I-hPRL was intravenously injected to a rat and the plasma samples subsequently obtained were fractionated. In the plasma at 5 min. after injection, 49% of radioactivity was eluted at the void volume on gel filtration. Monomeric <SUP>125</SUP> I-hPRL diminished sharply in plasma samples at following time intervals, and accounted for 3.5% of the recovered radioactivity at 60 min. after injection. Similarly a considerable proportion of 125I-hPRL was converted to the large molecular (peak I) form after incubation in human sera at 37°C for 3 hours. In sera from patients with liver cirrhosis, 8.0 ± 2.2% (mean ± SD) of radioactivity was eluted at the void volume on gel chromatography. In contrast 14.7 ± 1.6% of <SUP>125</SUP> I-hPRL was converted to the peak I form after incubation in sera of normal subjects, exhibiting significantly higher percentages compared with sera from patients with liver cirrhosis. <BR>These results suggest that the distribution of heterogeneous components of human PRL are variable in different circumstances and the biological activity of PRL may not always parallel the whole serum concentration, and that one of the sources of the large molecular form of circulating PRL is peripheral conversion from monomeric PRL.

• 一般社団法人 日本内分泌学会の論文

著者

• 片岡 邦孝

  名古屋大学医学部第一内科

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• ヒトProlactin (PRL) のHeterogeneityに関する研究

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