Calcium accumulation by subcellular fractions from vascular smooth muscle

Heß, Michael; Ford, George D.

doi:10.1016/0022-2828(74)90056-x

Cited by 47 publications

(20 citation statements)

References 22 publications

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“…Hence, we were also unable to obtain a consistently linear plot of the kinetic data using either a Lineweaver-Burke or an Eadie plot. There are numerous possible explanations for this lack of linearity: the mitochondria may have more than one uptake mechanism (25) or exhibit cooperativity (26) or the fraction may have too much vesicular contamination (16). However, our data, as shown in Figure 3, do show that at free calcium levels of 10" 6 M, the mitochondria-enriched fraction's relative ability to compete for cytoplasmic free calcium is reduced.…”

contrasting

confidence: 41%

“…These results leave many questions unanswered, not the least of which is the precise nature of this vesicular fraction. The characteristic enzymes associated with the vesicular fraction show a good amount of heterogeneity (16). It is tempting to compare this fraction with the early fragmented sarcoplasmic reticulum obtained from cardiac muscle (33)(34), since the vesicular fraction does have a high enrichment of Ca-ATPase and is sensitive to oxalate to enhance its calcium uptake.…”

Section: Discussionmentioning

confidence: 99%

“…A vesicular fraction capable of actively accumulating calcium was prepared from the medial muscularis of the bovine aorta using a previously described method (16). The muscularis was stripped free of adventitia and intima, finely diced with scissors, and homogenized for 1 minute with a Sorval Omnimixer in an extraction solution of 0.3M sucrose and 10 mti imidazole (pH 7.0).…”

Section: Methodsmentioning

confidence: 99%

“…In this spirit, several workers have reported the preparation of subcellular fragments capable of actively sequestering calcium from the rabbit aorta (13,14) and the canine aorta (15). We have also reported the preparation and characterization of two such fractions, one enriched in mitochondria and one enriched in vesicular material, from the bovine aorta (16). In the experiments reported in this study, we examined some of the questions about the calcium capacity and the calcium uptake kinetics of these aortic fractions.…”

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confidence: 99%

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Calcium-accumulating properties of subcellular fractions of bovine vascular smooth muscle.

Ford¹,

Heß²

1975

Circulation Research

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This study examined the calcium transport properties of two subcellular fractions of bovine aorta obtained by differential centrifugation. The vesicular fraction had a high-affinity (K m = 1.05 x 10~6M) calcium transport mechanism which could be potentiated by using the calcium-precipitating anion, oxalate. The mitochondriaenriched fraction's calcium transport system had a lower affinity for calcium than did that of the vesicular fraction. The calcium capacity of the vesicular fraction was determined by comparing the steady-state calcium uptake in the presence of oxalate in the whole homogenate with the same uptake by the vesicular fraction alone. A calcium capacity of about 100 /imoles Ca 2+ /kg aorta was obtained. It is concluded that the vesicular fraction has all of the properties of a major site of subcellular calcium regulation in vascular smooth muscle.• It is generally accepted that intracellular free calcium is the connection between stimulation and contraction in vascular smooth muscle (1, 2). However, the identification of the sources and sinks of the activator calcium remains an unsettled question. Numerous indirect experiments have shown that at least part of the activator calcium is intracellular in origin (1-4). Recent electron microscopic studies indicate that there are at least two different subcellular organelles potentially capable of serving as intracellular sinks for calcium: one is the mitochondria and the other is the sarcoplasmic reticulum (5-7). Both of these structures are capable of sequestering the divalent ion strontium in contracting muscle, and the mitochondria can also sequester barium. To determine if these or any other subcellular structures are capable of playing major roles in the regulation of the intracellular calcium concentration of vascular smooth muscle, numerous questions must be answered. Are these structures capable of accumulating calcium at the very low cytoplasmic level (10~5M) sufficient for maximal activation of the contractile process (8)? If they are capable of sequestering calcium at this low level, what is the relative competitive position of each structure? Can these structures, alone or in

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contrasting

confidence: 41%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Calcium-accumulating properties of subcellular fractions of bovine vascular smooth muscle.

Ford¹,

Heß²

1975

Circulation Research

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“…Recent studies with vascular smooth muscle have indicated that reten tion of Ca44 may occur within specific cellular structures that have a role in regulating Ca44 important for initiation and maintenance of mechanical responsiveness [9,16,24,25], Furthermore, contractile responses in the absence of extracellular Ca44 can be correlated with the volume of sarco plasmic reticulum [9]. Since the rabbit mesenteric artery has a lower sarco plasmic reticulum content than does the rabbit aorta [9], the large ex changeable 43Ca fraction observed in the dog terminal mesenteric arteries might, in an analogous manner, be of direct importance for the maintenance of contractile responses in these highly reactive resistance vessels.…”

Section: Discussionmentioning

confidence: 99%

Effects of Neomycin on <sup>45</sup>Ca Binding and Distribution in Canine Arteries

Goodman¹,

Adams²,

Weiss³

1975

J Vasc Res

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The effects of neomycin (7.0 mM) on 45Ca movements and distribution were investigated in canine aortae and in canine carotid and terminal mesenteric arteries. Uptake of ⁴⁵Ca was measured in calcium-free solution; the ⁴⁵Ca tissue spaces in the carotid and terminal mesenteric arteries were 2–4 times greater than those observed in the aorta. Exposure of the aortae and the terminal mesenteric arteries to 1.5 mM Ca⁺⁺ during the washout elicited large increases in ⁴⁵Ca efflux in both preparations (increase in terminal mesenteric > aorta). Moreover, in all three arterial preparations, neomycin reduced ⁴⁵Ca uptake and induced a sustained increase in ⁴⁵Ca efflux (effects on terminal mesenteric > carotid > aorta). The terminal mesenteric and carotid arteries may accumulate and bind ⁴⁵Ca at superficial membrane sites (readily exchangeable ⁴⁵Ca) to a greater degree than does the aorta. If Ca⁺⁺ located at these membrane sites contributes directly to the maintenance of mechanical responsiveness, then agents which alter membrane binding of Ca⁺⁺ (e.g. neomycin) may exert a stronger action on these highly reactive vessels. Thus, contractile responsiveness in peripheral arteries may depend upon depots of superficially bound Ca⁺⁺ to a greater degree than in the more centrally located aorta.

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Electron microscopic localization of calcium in vascular smooth muscle

et al. 1975

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Potassium pyroantimonate has been employed in this study to localize calcium in the vascular smooth muscle of the thoracic aorta of the rabbit. The pyroantimonate ion precipitates sodium, magnesium and calcium. Incubation of theisolated thoracic aorta in a high potassium bathing medium which does not contain sodium, magnesium or calcium depletes the tissue of sodium. Addition of 10.8 mM CaC12 to the incubation medium results in well-localized depositions of reaction product, presumably that of calcium pyroantimonate, in mitochondria, sarcoplasmic reticulum, and at the plasma membrane. Some or all of these organelles may, therefore, play a vital role in the contraction-relaxation cycle of vascular smooth muscle.

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Calcium accumulation by subcellular fractions from vascular smooth muscle

Cited by 47 publications

References 22 publications

Calcium-accumulating properties of subcellular fractions of bovine vascular smooth muscle.

Calcium-accumulating properties of subcellular fractions of bovine vascular smooth muscle.

Effects of Neomycin on <sup>45</sup>Ca Binding and Distribution in Canine Arteries

Electron microscopic localization of calcium in vascular smooth muscle

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