Heterogeneous Forms of Immunoreactive Galanin in Human Plasma; Higher Levels in Men than in Women

E. Grenbäck; A.-L. Hulting; E. Bucht

doi:10.1055/s-2005-861473

Hormone and Metabolic Research, Table of Contents

Horm Metab Res 2005; 37(5): 290-296
DOI: 10.1055/s-2005-861473

Original Clinical

Heterogeneous Forms of Immunoreactive Galanin in Human Plasma; Higher Levels in Men than in Women

E. Grenbäck¹ , A.-L. Hulting¹ , E. Bucht¹

¹ Department of Molecular Medicine, Endocrine and Diabetes Unit, Karolinska Hospital, Stockholm, Sweden

Abstract

Galanin, a neuropeptide, has important effects on hormone secretion from the hypothalamus and pituitary, and may also be involved in important biological processes such as pain, memory, and food intake. Yet, there is limited knowledge about how these processes are reflected by circulating galanin. To study the levels and molecular forms of galanin in the human circulation, plasma was analysed from 27 healthy subjects, 14 women and 13 men, using two extraction methods and a specific radioimmunoassay for human galanin. After extraction on Sep Pak C-18 columns, plasma galanin-like immunoreactivity (galanin-LI) in the healthy men was 6.3 ± 2.5 pmol/l (mean ± SD, n = 12), which was higher than in the women, 4.1 ± 1.5 pmol/l (n = 14, p = 0.010). A small increase in galanin-LI was seen with age in the women (r = 0.54, p < 0.05) but there was no significant difference between pre- and postmenopausal women. Galanin immunoreactivity after Sep Pak and immunoextraction correlated (r = 0.74, p < 0.001) the levels being higher after immunoextraction (p < 0.001). Gel chromatography disclosed heterogeneity of circulating galanin-LI with the majority eluting as homologs with a molecular weight higher than synthetic human galanin. Homologs smaller than galanin were also found. Sep Pak C-18 extraction eliminated the majority of the higher molecular forms. In conclusion, circulating galanin-LI was found to be higher in men and to be present mainly as molecular forms larger than synthetic galanin.

Key words

Immunoextraction - Sep Pak C-18 - Gel chromatography - Radioimmunoassay

Full Text

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E. Grenbäck

Dept. of Molecular Medicine · Endocrine and Diabetes Unit · Karolinska Hospital, S-17176 Stockholm, Sweden

Phone: 46 (8) 517 730 65

Fax: 46 (8) 517 730 96

Email: Eva.Grenback@karolinska.se