LH isoform profiles during short-term pulsatile LHRH administration in elderly men.
LH isoform profiles were analyzed in sera resolved with isoelectrofocusing from 5 elderly men (age 70.6 +/- 2.95) and 5 young adult men (age 28.2 +/- 1.24), by using polyclonal antibodies (RIA), monoclonal antibodies directed against the beta-subunits (IRMA) and in vitro LH bioassay. Despite the fact that the elderly had lower testosterone levels than the young (293 +/- 38 vs 512 +/- 77 ng/dl, p < 0.05), no differences were noted in the isoforms detected by any of the assays, although each assay yielded a characteristic profile. Indeed, RIA showed most LH in the acidic range, while IRMA revealed LH profiles with a major peak in the basic range, thus resembling the profiles determined by means of the bioassay. In the elderly, the profiles were also analyzed on day 7 and day 14 of short-term pulsatile sc LHRH administration (150 ng/bw/120 min). Only the LH bioassay detected an LHRH-induced shift to more basic and bioactive forms; these changes accompanied an increased in testosterone levels on day 7 (396 +/- 83 ng/dl, p < 0.05 vs day 0) and on day 14 (320 +/- 58 ng/dl NS vs day 0). Our data suggest that: 1) the profiles obtained in young and elderly subjects are similar, irrespective of the antisera used; 2) as a result of treatment with LHRH in the elderly an increase in T levels occurs, possibly due to the observed changes in LH bioactivity; 3) the in vitro LH bioassay appears to be the most sensitive assay in detecting such changes, which consisted of an enrichment in more basic and bioactive glycoforms.
Giusti
M
M
Dipartimento di Scienze Endocrine e Metaboliche, University of Genova, Italy.
Valenti
S
S
Guido
R
R
Cuttica
C M
CM
Foppiani
L
L
Giordano
G
G
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001681:Biological Assay / Q000706:statistics & numerical data; D004334:Drug Administration Schedule; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D006062:Gonadotropins / Q000097:blood; D006801:Humans; D015592:Immunoradiometric Assay / Q000706:statistics & numerical data; D007279:Injections, Subcutaneous; D007536:Isomerism; D007986:Luteinizing Hormone / Q000097:blood* / Q000187:drug effects*; D008297:Male; D011673:Pulsatile Flow; D011863:Radioimmunoassay / Q000706:statistics & numerical data; D051381:Rats; D013739:Testosterone / Q000097:blood
D006062:Gonadotropins; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone