Structural and functional responses to prolonged hindlimb suspension in rat muscle

Abstract

The purpose of this study was to investigate alterations in structural and functional properties in the soleus (SOL) and extensor digitorum longus (EDL) muscles of rats after 1, 2, and 5 wk of tail suspension. Maximal O2 uptake was 19% lower after 5 wk suspension. Loss of muscle mass was greater in SOL (63%) than in EDL (22%) muscle. A reduction of type I distribution was accompanied by an increase of intermediate fiber subgroups (int I in SOL, int II in EDL). The cross-sectional area of all three fiber types was reduced by hypokinesia. The decrease in capillaries per fiber in SOL was greater than the decrease in citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities after 5 wk. No alteration in lactate dehydrogenase activity was noted. In EDL, no changes in fiber area, capillarization, and enzymatic activities occurred. Energy charge remained unchanged (0.91) whatever the muscle. These results suggest that type I fibers showed an earlier and greater susceptibility than type II fibers to suspension which is also accompanied by a decreased aerobic capacity.

Modelo de suspensão pela cauda e seu efeito em algumas propriedades mecânicas do osso do rato

“…In Desplanches et al (3) results, the animals presented a higher loss of weight during the first days of suspension but, after fourteen days, most of them restored the lost weight.…”

“…Nos resultados de Desplanches et al (3) , os animais tiveram maior perda de peso nos primeiros dias de suspensão mas, após quatorze dias, a maioria deles recuperou o peso perdido.…”

Ultrastructural and metabolic profiles on single muscle fibers of different types after hindlimb suspension in rats.

“…The suspended rats were able to use forelimbs to move around a pivot, permitting access to food and water freely. Apparent changes in the structure and function of muscle fibers after 2-week suspension have been reported (DESPLANCHES et al, 1987;ELDER and MCCOMAS, 1987). Therefore, we decided that a period of 2-week suspension hypokinesia in this study would be appropriate.…”

Differential Effects of Astaxanthin on Oxidative Key Enzyme and Capillarization in the Deep and Superficial Layers of Unloading-induced Atrophied Muscle

“…Some studies have reported that unloading causes oxidative stress such as overexpression of reactive oxygen species, leading to capillary regression in the atrophied muscle 15,16) . Although elevation of reactive oxygen species was not observed in the present study, the overexpression of reactive oxygen species has been shown in similarly atrophied muscles in other studies 4,5) , and in the present study, atrophied plantaris muscle may have been exposed to oxidative stress.…”