title: Passive length-force properties of senescent diaphragm: relationship with collagen characteristics.
abstract: The purpose of this study was to examine the effect of aging on collagen concentration and extent of nonreducible collagen cross-linking as well as with the passive length-force relationship of the diaphragm muscle. Midcostal diaphragm muscle strips from young (6 mo) and senescent (24 mo) Fischer 344 rats were perfused in a tissue bath containing mammalian Ringers solution (25 degrees C) aerated with 95% O2-5% CO2. The segments were lengthened and shortened from 85 to 115% of optimal length (L(o)) at a constant velocity (0.6 L(o)/s), and the passive force was measured. Hydroxyproline (HYP) and the mature nonreducible collagen cross-link, hydroxylysylpyridinoline (HP), were measured by high-pressure liquid chromatography. The resting force at Lo did not differ between young and senescent diaphragm muscles. However, the senescent diaphragm exhibited greater passive force compared with the young (P < 0.05) at lengths > 110% of L(o). High-pressure liquid chromatography analysis revealed a higher concentration of HYP in the senescent compared with the young diaphragm (9.32 +/- 0.83 and 6.59 +/- 0.78 g HYP/mg dry wt, respectively; P < 0.05). Additionally, the content of HP was greater in the senescent compared with the young diaphragm (1.16 +/- 0.05 and 0.91 +/- 0.05 mol HP/mol collagen, respectively; P < 0.05). These results suggest that diaphragm collagen metabolism, maturation, and the passive length-force characteristics of the muscle are altered with senescence.
authors.affiliation: Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905.
authors.forename: L E
authors.initials: LE
authors.lastname: Gosselin
authors.forename: D A
authors.initials: DA
authors.lastname: Martinez
authors.forename: A C
authors.initials: AC
authors.lastname: Vailas
authors.forename: G C
authors.initials: GC
authors.lastname: Sieck
mesh_terms: D000375:Aging / Q000502:physiology*; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000737:chemistry / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003964:Diaphragm / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D004558:Electric Stimulation; D006909:Hydroxyproline / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D024510:Muscle Development; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D000596:Amino Acids; D003432:Cross-Linking Reagents; C015484:pyridinoline; D003094:Collagen; D006909:Hydroxyproline