Spaceflight effects on [beta]-adrenoceptor and metabolic properties
in rat plantaris.
Ohira, Y., W. Yasui, F. Kariya, T. Tanaka, I. Kitajima, I. Maruyama,
S. Nagaoka, C. Sekiguchi, and W. E. Hinds.
Dept. Physiol. Biomech., Nat'l. Inst. Fit. Sports, Kanoya City,
891-23, Dept. Molec. Lab. Med., Kagoshima Univ. Sch. Med., Kagoshima
City 890, Space Exp. Group, Nat'l. Space Develop. Agency Japan,
Tsukuba City 305, Japan, and Space Life Sci. Payloads Office, Ames
Res. Ctr, Moffett Field, Ca. 94035-1000, U.S.A.
APStracts 2:0301A, 1995.
Effects of 14 days of spaceflight on [beta]-adrenoceptor ([beta]-AR),
mitochondrial enzyme activities, and fiber type composition were
studied in plantaris muscles of male adult Sprague Dawley rats. The
[beta]-AR was analyzed in cross-sections by quantitative
autoradiography. The maximum binding capacity (Bmax) of [beta]-AR was
significantly lowered ( 29%) after flight, but the recovery was not
completed within 9 days in 1-G environment. Since the dissociation
constant remained unchanged, it is suggested that the changes in the
Bmax were caused by the alteration of receptor number. The activities
of succinate dehydrogenase (SDH) measured in whole-homogenates were
subnormal ( -24%) in muscles sampled 5 hrs after flight, but they
were normalized during 9 days of recovery. The percent composition of
fiber types and [beta]-hydroxyacyl CoA dehydrogenase (HAD) activity
did not change by spaceflight significantly. It is suggested that the
spaceflight-induced decrease of the Bmax of [beta]-AR in plantaris
was accompanied by a lowered activity of a mitochondrial inner
membrane enzyme, SDH, but not a matrix enzyme, HAD.
Received 3 March 1995; accepted in final form 13 June 1995.
APS Manuscript Number A238-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.