title: The bio/immuno ratio of serum luteinizing hormone increases after orchiectomy in prostatic cancer patients and is associated with decreased molecular weight and appearance of isohormones with alkaline pI values.
abstract: Serum concentrations of bioactive (B) and immunoreactive (I) luteinizing hormone (LH) were determined in six patients with prostatic cancer before castration and at frequent intervals after the operation up to 6 mo. B-LH increased in 6 mo from 11 +/- 1 to 90 +/- 9 (mean +/- SEM, n = 6) IU/liter (p less than 0.01), and I-LH from 9 +/- 1 to 37 +/- 5 IU/liter (p less than 0.01). Accordingly, a significant increase in the B/I ratio of LH occurred at the same time, from 1.3 +/- 0.1 to 2.4 +/- 0.2 (p less than 0.01). To elucidate the molecular basis of the B/I ratio change, serum samples obtained before and 2-6 mo after orchiectomy were fractionated by gel filtration and chromatofocusing, and the eluted fractions were analyzed for B-LH and I-LH. In gel filtration, the fractions with the highest B-LH and I-LH contents were eluted later in the post-castration samples than in the pretreatment samples (mean Ve/Vo 1.31-1.32 vs. 1.26-1.28; p less than 0.02-0.01), indicating a small reduction in the average Mr of the circulating LH after castration. In chromatofocusing, a single major peak of immunoreactivity with a pI value of 7.4 was identified before castration, but in post-castration samples, a significantly large proportion of the immunoreactivity was eluted in the alkaline pI range 7.4-9 (22.2 +/- 2.4% before, 56.5 +/- 5.2% after castration, p less than 0.05). These findings indicate that after castration, the increased B/I ratio of serum LH is explained by a preferential increase in isohormones with slightly reduced molecular weights and alkaline pI values.
authors.affiliation: Department of Physiology, University of Turku, Finland.
authors.forename: A M
authors.initials: AM
authors.lastname: Haavisto
authors.forename: N
authors.initials: N
authors.lastname: Simberg
authors.forename: I
authors.initials: I
authors.lastname: Huhtaniemi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002850:Chromatography, Gel; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000097:blood* / Q000276:immunology; D008297:Male; D009919:Orchiectomy; D011471:Prostatic Neoplasms / Q000097:blood / Q000601:surgery*; D011863:Radioimmunoassay
chemical_list: D007986:Luteinizing Hormone