Histochemical heterogeneity of intrafusal muscle fibres in slow and fast skeletal muscles of the rat

Abstract

Intrafusal muscle fibres of the slow soleus (Sol) and fast vastus lateralis (VL) muscles of the rat were studied histochemically. Serial transverse sections were incubated for the localization of succinate dehydrogenase (SDH), alpha glycerophosphate dehydrogenase (GPD) and adenosine triphosphatase (ATPase). The latter was examined further after preincubation in acidic solution held at either low or room temperature (RT). The bag2 intrafusal fibres in both muscles displayed high regular and acid stable ATPase, but low SHD and GPD activities. Bag1 intrafusal fibres showed low to moderate regular ATPase, a regional heterogeneity after RT acid preincubation (low activity in juxtaequatorial and high in polar zones), moderate SDH, but low GPD reactions. In both muscles the chain fibres usually exhibited high ATPase for both regular and cold acid preincubated reactions, but usually low activity after RT acid preincubation; they had high SDH but variable GPD activities. In Sol muscle, however, approximately 25% of spindles contained chain fibres that showed high acid-stable ATPase reaction after both cold and RT acid preincubation. In contrast, chain fibres in some VL spindles had a characteristically low ATPase reaction even after cold acid preincubation. This study, therefore, has delineated the existence of an inherent heterogeneity among chain fibres (with respect to their histochemical reactions) in muscle spindles located within slow and fast muscles and also between those found within populations of either Sol or VL muscle spindles.

Expression of Myosin Heavy Chain Isoforms Along Intrafusal Fibers of Rat Soleus Muscle Spindles After 14 Days of Hindlimb Unloading

“…Nuclear bag2 fibers have an acid-stable ATPase activity along their length and an intracapsular alkaline-stable ATPase activity that is lost beyond the capsular sleeve. Nuclear chain fibers have low acid and high alkaline ATPase activities along their entire length (Kucera et al 1978;Khan and Soukup 1988). The nuclear bag1 and bag2 fibers were labeled with both ALD58 MAb, specific for the slow-tonic MHC isoform, and F88 MAb, specific for the ␣ -cardiac MHC isoform.…”

Expression of myosin heavy chain isoforms and myogenesis of intrafusal fibres in rat muscle spindles

“…The mATPase activity is not uniform along the length of the intrafusal fibres ( Fig. 3) in rat (Khan and Soukup, 1988;Kucera et al, 1978;Soukup, 1976;Soukup et al, 1979;Yellin, 19741, cat (Banks et al, 1977;Kucera, 19811, and human muscle spindles (Eriksson and Thornell, 1985;Eriksson et al, 1993;Kucera and Dorovini-Zis, 1979;Soukup et al, 1992;Thornell et al, 1988a).…”

Glycogen depletion in intrafusal fibres in rats during short‐duration high‐intensity treadmill running

“…The fibre typing of intrafusal muscle fibres was based on previous studies of the histochemical and morphological features (Yellin 1974, Banks et al. 1977, Khan & Soukup 1988), and the total complement of four intrafusal fibres could be traced along their complete length throughout the A, B and C regions of the muscle spindles. Under the conditions of our experiments, among the three types of intrafusal fibres the glycogen content of bag 2 fibres decreased first in the early phase of exercise.…”

“…On the other hand, bag 2 fibres usually have lower SDH activities and glycogen contents than bag 1 and chain fibres (Banks et al. 1977, Kucera 1980, Khan & Soukup 1988, Yoshimura et al. 1996).…”