Testosterone: short- and long-term effects on diaphragm muscle in
castrated and sexually normal male rats.
Prezant, David J., Manoj L. Karwa, Helen H. Kim, Diane Maggiore,
Virginia Chung, David E. Valentine.
Department of Medicine, Pulmonary Division and the Department of
Physiology and Biophysics, Albert Einstein College of Medicine,
Montefiore Med.Ctr.
APStracts 3:0414A, 1996.
The effects of short- and long-term testosterone absence or treatment
on the dia phragm were studied in castrated and sexually normal male
rats. Compared to controls (untreated normal males), testosterone
absence or treatment did not significantly affect costal weight. In
untreated castrated males, there were significant decreases in
specific forces, type II fiber cross-sectional area (CSA) and myosin
heavy chain isoform MHC-2B after 2.5 wk. In castrated males receiving
testosterone, there were significant increases in specific forces,
type II total fiber proportional area and MHC-2all fast isoforms
after 2.5 wk. In normal males receiving testosterone, the only
significant finding was an increase in MHC-2B after 2.5 wk. Across
all groups, there was close correlation between increases in maxi mum
tetanic forces and MHC-2all fast isoforms. Changes in diaphragm
function and composition were closely related to changes in serum
testosterone levels at 2.5 wk. The lack of significant change in
diaphragm function at 10 wk, occurred despite similar changes in
serum testosterone levels and diaphragm composition to those at 2.5
wk. These findings support our hypothesis that testosterone's effects
are dependent on basal circulating andro gen levels and study
duration.
Received 24 June 1996; accepted in final form 20 August 1996.
APS Manuscript Number A583-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996