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This Article Full Text Full Text (PDF) All Versions of this Article: 293/1/H548    most recent 00134.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Sandoval, R. J. Articles by Pearce, W. J. Search for Related Content PubMed PubMed Citation Articles by Sandoval, R. J. Articles by Pearce, W. J.

Myogenic contractility is more dependent on myofilament calcium sensitization in term fetal than adult ovine cerebral arteries

Department of Physiology and Pharmacology, Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, California

Submitted 1 February 2007 ; accepted in final form 22 March 2007

Regulation of cytosolic calcium and myofilament calcium sensitivity varies considerably with postnatal age in cerebral arteries. Because these mechanisms also govern myogenic tone, the present study used graded stretch to examine the hypothesis that myogenic tone is less dependent on calcium influx and more dependent on myofilament calcium sensitization in term fetal compared with adult cerebral arteries. Term fetal and adult posterior communicating cerebral arteries exhibited similar myogenic responses, with peak tensions averaging 24 and 26% of maximum contractile force produced in any given tissue in response to an isotonic Krebs buffer containing 122 mM K⁺ (K_max) at optimum stretch ratios (working diameter/unstressed diameter) of 2.19 and 2.23, respectively. Graded stretch increased cytosolic Ca²⁺ concentration at stretch ratios >2.0 in adult arteries, but increased Ca²⁺ concentration only at stretch ratios >2.3 in fetal arteries. In permeabilized arteries, myogenic tone peaked at a stretch ratio of 2.1 in both fetal and adult arteries. The fetal %K_max values at peak myogenic tone were not significantly different at either pCa 7.0 (23%) or pCa 5.5 (25%) but were significantly less at pCa 8.0 (8.4 ± 2.3%). Conversely, adult %K_max values at peak myogenic tone were significantly less at both pCa 8.0 (10.4 ± 1.8%) and pCa 7.0 (16%) than at pCa 5.5 (27%). The maximal extents of stretch-induced increases in myosin light chain phosphorylation in intact fetal (20%) and adult (17%) arteries were similar. The data demonstrate that the cerebrovascular myogenic response is highly conserved during postnatal maturation but is mediated differently in fetal and adult cerebral arteries.

-escin; fura 2; length-tension relations; myosin light chain phosphorylation

This article has been cited by other articles:

				R. J. Sandoval, E. R. Injeti, W. T. Gerthoffer, and W. J. Pearce Postnatal maturation modulates relationships among cytosolic Ca2+, myosin light chain phosphorylation, and contractile tone in ovine cerebral arteries Am J Physiol Heart Circ Physiol, October 1, 2007; 293(4): H2183 - H2192. [Abstract] [Full Text] [PDF]