Determination of skeletal muscle calpain and calpastatin activities during maturation.
Our objectives were to characterize events underlying changes in skeletal muscle calpain and calpastatin activities, using maturation as a model. Muscle samples were taken from rabbits of four ages (newborn and 1, 2, and 5 mo old). Concentrations of RNA and protein and activities of calpains I and II and calpastatin were determined. Steady-state concentrations of mRNAs encoding calpain I, calpain II, calpastatin, alpha- and beta-tubulin, and beta-actin were determined using Northern blot analysis. Calpain and calpastatin activities declined markedly between birth and 1 mo of age and remained unchanged thereafter. Several factors accounted for the neonatal losses of calpains and calpastatin. First, muscle protein concentration increased between birth and 1 mo of age and diluted calpain and calpastatin specific activities. Second, there was a marked reduction of muscle RNA concentration between birth and 1 mo of age, which indicates that protein synthetic capacity declined with age. Finally, calpastatin mRNA concentration declined between birth and 1 mo of age and further contributed to developmental losses of calpastatin activity. Calpain I mRNA concentration was unaffected by age, and although calpain II mRNA concentration declined with age, losses were not detected between birth and 1 mo; hence age-related changes in calpain I and II activities are not mediated at the mRNA level. The age-related reductions in calpain II and calpastatin mRNA concentrations resembled age-related changes in alpha- and beta-tubulin and beta-actin mRNA concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
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Department of Animal Science, Oregon State University, Corvallis 97331-6702.
Forsberg
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D000375:Aging / Q000378:metabolism*; D000818:Animals; D015152:Blotting, Northern; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002154:Calpain / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D024510:Muscle Development; D009132:Muscles / Q000033:anatomy & histology / Q000378:metabolism*; D009929:Organ Size; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits
D002135:Calcium-Binding Proteins; D012333:RNA, Messenger; C033668:calpastatin; D002154:Calpain