Muscle IGF-I Ea, MGF, and myostatin mRNA expressions after compensatory overload

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Pflugers Arch. 2006 Aug 29

Muscle IGF-I Ea, MGF, and myostatin mRNA expressions after

compensatory overload in hypophysectomized rats.

Yamaguchi A, Fujikawa T, Shimada S, Kanbayashi I, Tateoka M, Soya H,

Takeda H, Morita I, Matsubara K, Hirai T.

School of Dentistry, Health Sciences University of Hokkaido,

Kanazawa, Ishikari-Tobetsu, Hokkaido, 061-0293, Japan, yama@hoku-iryo-

u.ac.jp.

To determine whether IGF-I Ea, MGF, and myostatin mRNAs are related

to GH-independent overload-induced muscle growth, we examined the

expressions of IGF-I Ea and MGF mRNAs in the plantaris muscle after

compensatory overload in hypophysectomized rats. The muscles were

divided into four groups: normal-control, normal-overloaded,

hypophysectomized-control, and hypophysectomized-overloaded.

The weights of the plantaris muscle in the normal-overloaded were

significantly higher than those of the normal-control. The weights of

the hypophysectomized-overloaded were also significantly higher than

those of the hypophysectomized-control. IGF-I Ea and MGF mRNAs in

normal-overloaded and hypophysectomized-overloaded 3 days after

overload were significantly higher than those of normal-control and

hypophysectomized-control, respectively. Myostatin mRNAs in normal-

overloaded and hypophysectomized-overloaded 3 days after the overload

were significantly lower than those of normal-control and

hypophysectomized-control, respectively.

Thus, it was shown that IGF-I Ea, MGF, and myostatin mRNAs were

expressed in association with muscle enlargement after compensatory

overload independently of pituitary state. These observations suggest

that the expression of IGF-I Ea, MGF, and myostatin mRNAs due to

compensatory overload would be associated in a growth-hormone-

independent manner.