AJP - Endocrinology and Metabolism, Vol 241, Issue 3 246-E250, Copyright © 1981 by American Physiological Society
Evidence that brain aromatization regulates LH secretion in the male dog
T. J. Worgul, R. J. Santen, E. Samojlik, G. Irwin and R. E. Falvo
A variety of data suggest an independent role for androgens and estrogens
in the regulation of luteinizing hormone (LH) secretion in the male.
Estrogens, in the male are primarily derived from testicular androgens that
are aromatized both in peripheral tissues and in the CNS. Our prior data
suggested a pharmacologic regimen that blocked CNS aromatization without
lowering peripheral estrogen or testosterone levels. Such experimental
conditions would permit assessment of the relative roles of CNS versus
peripheral aromatization in the regulation of LH secretion. We utilized
this regimen (aminoglutethimide, a potent aromatase inhibitor, and
hydrocortisone) in seven adult male dogs for 14 days. Plasma LH rose to
castrate levels, 450% above control values on days 7 and 14. These LH
increments stimulated similar rises in androstenedione, testosterone, and
dihydrotestosterone. In contrast, plasma estrone and estradiol
concentrations remained constant. The induction of castrate LH levels
without a concomitant fall in peripheral androgens or estrogens is best
explained by a block of central aromatization and thus a reduction in local
hypothalamic concentrations. We conclude that aromatization in the CNS
rather than peripheral tissues is the more important site with respect to
LH negative feedback in the male dog.
