AJP - Endocrinology and Metabolism, Vol 238, Issue 6 518-E523, Copyright © 1980 by American Physiological Society
Influence of thyroid status on skeletal muscle LPL activity and TG uptake
H. Kaciuba-Uscilko, G. A. Dudley and R. L. Terjung
The influence of thyroid status on the clearance of chylomicron 14C-labeled
triglycerides (14C-TG), the fractional uptake of 14C-TG, and activity of
lipoprotein lipase (LPL) in the different skeletal muscle fiber types was
evaluated in pentobarbital-anesthetized rats. The turnover of plasma TG was
approximately fourfold greater in the hyperthyroid (HyperT) compared to
either euthyroid (EUT) or hypothyroid (HypoT) animals. The uptake of 14C-TG
was increased in slow-twitch red and fast-twitch red muscle sections of the
HyperT group and normal in the HypoT group. The changes in LPL activity in
these two fiber types were inversely related to thyroid influence, with
decreases found in the HyperT group and increases found in the HypoT group.
Thus, the uptake of 14C-TG in these high-oxidative fibers, relative to the
LPL activity, varied directly with thyroid influence. As a result, the
normal linear relationship, apparent for the different types of skeletal
muscle, between LPL activity measured in vitro and TG uptake determined in
situ was not maintained.
