AJP - Endocrinology and Metabolism, Vol 242, Issue 3 201-E205, Copyright © 1982 by American Physiological Society
Responses of ram lambs to active immunization against testosterone and luteinizing hormone-releasing hormone
B. D. Schanbacher
Active immunization of young ram lambs against testosterone and luteinizing
hormone-releasing hormone (LHRH) was shown to block the growth attributes
characteristic of intact ram lambs. Testosterone and LHRH-immunized lambs
grew at a slower rate and converted feed to live weight gain less
efficiently than albumin-immunized controls. Lambs immunized against
testosterone and LHRH had high antibody titers for their respective
antigens. Moreover, testosterone-immunized lambs had high serum
concentrations of luteinizing hormone (LH) and testosterone, whereas
LHRH-immunized lambs had low to nondetectable serum concentrations of these
hormones. Release of LH and testosterone following the intravenous
administration of LHRH (250 ng) was absent in LHRH-immunized lambs, but
quantitatively similar for intact and albumin-immunized control lambs.
Testosterone-immunized lambs responded as did conventional castrates with a
large LH release, but testosterone concentrations were unchanged. These
findings are discussed relative to the integrity of the
hypothalamic-pituitary-testicular endocrine axis and the importance of
gonadotropin support for normal testicular development. These data show
that LHRH immunoneutralization effectively retards testicular development
and produces a castration effect in young ram lambs.
