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 increase 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: I)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. (C) 1997, Editrice Kurtis.