Intracellular calcium ([Ca2+]i) release from endoplasmic reticulum (ER) stores plays an important role in cell signaling. These stores are rapidly refilled via voltage-gated calcium channels or spontaneously via store-operated calcium channels and subsequent pumping by ER Ca2+-ATPases. Calcium release is triggered by the activation of the ryanodine receptor (RyR) channels and their function is in part dependent on their expression. We analyzed the [Ca2+]i transients in fura 2-loaded superior cervical ganglion (SCG) cells from 6, 12, 20, and 24-month-old Fischer 344 rats for their ability to rapidly and spontaneously refill. For rapid refilling, the percent difference between the peak and rate of rise of the first and second caffeine-evoked [Ca2+]i transient significantly declined with age. Spontaneous refilling significantly declined from 12-24 month-old F-344 rats. These data suggest that the ability of SCG cells to sustain release of [Ca2+]i decline with age, but the underlying mechanisms that may be responsible for a decline in caffeineevoked release of Ca2+ remain elusive. Hence, we then focused on molecular characterization of the [Ca2+]i release channel. The pattern of genetic expression of RyRl, 2 and 3, has not been previously characterized with age in this model. In all age groups ryr 1 does not appear to be expressed in the SCG and ryr2 and ryr3 appear to be the predominantly transcribed isoforms in adult rat SCG. mRNA and protein levels for RyR2 did not change with age, however, the ryr3 mRNA and protein levels significantly increased from 6 to 12 months and then significantly declined from 12 to 24 months. These data alone, cannot account for the dramatic decline in caffeine-evoked Ca2+ release observed. However, if along with the changes in gene expression there was altered modulation, this may elucidate more clearly the reasons for the change in function of the RyR. In order to examine how the modulation of the RyR is affected by age, we then focused on modulators such as phosphorylation, and nNOS protein expression levels were analyzed for changes with age. There were no significant changes in the phosphorylation of the total RyRs with age. However, there was a significant increase in nNOS production from 6 months to 12 months and decline in protein expression of nNOS from the 12 months to 24 month-old rat SCG. We have demonstrated that aging significantly impacts the ability of the SCG to sustain calcium release, and exhibits altered genetic and protein expression of the major RyR isoforms, and nNOS protein expression. Taken together, these data suggest that the alteration in release of Ca2+ is due to a combination of altered filling of the ER and changes in the modulation of the release mechanism. The compromised ability of these neurons to sustain calcium signaling may possibly alter the overall function of adrenergic neurons innervating the cerebro vasculature.
Doctor of Philosophy (Medical Science)
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Library of Congress/MESH Subject Headings
Clacium -- physiology; Clacium -- pharmacology; Calcium Signaling -- physiology; Signal Transduction; Endoplasmic Reticulum. -- physiology; Aging; Cell Aging.
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Vanterpool, Conwin Kodel, "Effects of Advancing Age on ER Calcium Regulation in Rat Superior Cervical Ganglia" (2006). Loma Linda University Electronic Theses, Dissertations & Projects. 849.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives