Ca2+ uptake function of sarcoplasmic reticulum during contraction of rat arterial smooth muscles

2000 ◽  
Vol 404 (3) ◽  
pp. 315-326 ◽  
Author(s):  
Yukiko Nomura ◽  
Masahisa Asano
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Smooth Muscles

Sarcoplasmic Reticulum Function in Smooth Muscle

2010 ◽  
Vol 90 (1) ◽  
pp. 113-178 ◽  
Author(s):  
Susan Wray ◽  
Theodor Burdyga
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Physiological Activity ◽  
Smooth Muscles ◽  
Outward Current ◽  
Integrated Approach ◽  
Transient Outward Current ◽  
Coupling Mechanism ◽  
Striated Muscles ◽  
Development And Aging

The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a “one model fits all” approach to this subject, we have tried to synthesize conclusions wherever possible.

Sarcoplasmic reticulum and mitochondria as cation accumulation sites in smooth muscle

1973 ◽  
Vol 265 (867) ◽  
pp. 17-23 ◽  
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Divalent Cation ◽  
Electromechanical Coupling ◽  
Surface Membrane ◽  
Smooth Muscles ◽  
Relative Volume ◽  
Electron Dense Material ◽  
Tubular System ◽  
Central Elements

A tubular system of sarcoplasmic reticulum that is not penetrated by extracellular markers is described in vertebrate smooth muscles. The sarcoplasmic reticulum forms fenestrations around the surface vesicles and also forms close appositions (an approximately 10 to 12 nm gap traversed by periodic electron dense material) with the non-specialized surface membrane. The morphological couplings are considered to be the most probable sites of electromechanical coupling of the action potential to the twitch contraction. The relative volume of the sarcoplasmic reticulum varies in functionally different (tonic and phasic) smooth muscles, and correlates with the ability of the different smooth muscles to contract in the absence of extracellular calcium. Electron opaque deposits of strontium are accumulated by peripheral and central elements of the sarcoplasmic reticulum. The accumulation of strontium and barium by mitochondria raises the possibility that, in addition to the sarcoplasmic reticulum, mitochondria may play a role in the regulation of intracellular divalent cation levels in vertebrate smooth muscle.

scholarly journals SARCOPLASMIC RETICULUM AND EXCITATION-CONTRACTION COUPLING IN MAMMALIAN SMOOTH MUSCLES

1972 ◽  
Vol 52 (3) ◽  
pp. 690-718 ◽  
Author(s):  
Carrick E. Devine ◽  
Avril V. Somlyo ◽  
Andrew P. Somlyo
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Pulmonary Artery ◽  
Mesenteric Artery ◽  
Electromechanical Coupling ◽  
Surface Membrane ◽  
Main Pulmonary Artery ◽  
Smooth Muscles ◽  
Taenia Coli ◽  
Virtual Absence ◽  
Mesenteric Vein

The sarcoplasmic reticulum (SR) was studied in the smooth muscles of rabbit main pulmonary artery, mesenteric vein, aorta, mesenteric artery, taenia coli, guinea pig mesenteric artery, and human uterus, and correlated with contractions of the smooth muscles in Ca-free media. SR volumes were determined in main pulmonary artery (5.1%), aorta (5%), portal-anterior mesenteric vein (2.2%), taenia coli (2%), and mesenteric artery (1.8%): because of tangentially sectioned membranes these estimates are subject to a correction factor of up to +50% of the values measured. Smooth muscles that contained a relatively large volume of SR maintained significant contractile responses to drugs in the virtual absence of extracellular calcium at room temperatures, while smooth muscles that had less SR did not. The unequal maximal contractions of main pulmonary artery elicited by different drugs were also observed in Ca-free, high potassium-depolarizing solution, indicating that they were secondary to some mechanism independent of changes in membrane potential or calcium influx. Longitudinal tubules of SR run between and are fenestrated about groups of surface vesicles separated from each other by intervening dense bodies. Extracellular markers (ferritin and lanthanum) entered the surface vesicles, but not the SR. The peripheral SR formed couplings with the surface membrane: the two membranes were separated by gaps of approximately 10 nm traversed by electron-opaque connections suggestive of a periodicity of approximately 20–25 nm. These couplings are considered to be the probable sites of electromechanical coupling in twitch smooth muscles. Close contacts between the SR and the surface vesicles may have a similar function, or represent sites of calcium extrusion. The presence of both thick and thin myofilaments and of rough SR in smooth muscles supports the dual, contractile and morphogenetic, function of smooth muscle.

The sphincter pupillae of the guinea-pig: structure of muscle cells, intercellular relations and density of innervation

1974 ◽  
Vol 186 (1085) ◽  
pp. 369-386 ◽  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cell Surface ◽  
Guinea Pig ◽  
Cell Volume ◽  
Muscle Cell ◽  
Smooth Muscles ◽  
Volume Ratio ◽  
Muscle Cells ◽  
Structural Features ◽  
Full Cross Section

Compared with those of visceral and vascular smooth muscles, the smooth muscle cells of the sphincter pupillae of the guinea-pig show remarkable structural features. They are small, irregular in shape, and have a surface to volume ratio of about 2.73 (i. e. for every cubic micrometre of cell volume there are on average 2.73 µ m 2 of cell surface). Mitochon­dria constitute about 12% of the cell volume. Smooth sarcoplasmic reticulum is extremely well developed, lying underneath wide areas of the cell surface, between and around caveolae, and around most mitochondria. Stacks of cisternae of sarcoplasmic reticulum are present in superficial and deep regions of muscle cells. In some muscle cells rough sarcoplasmic reticulum is predominant. Thick, thin and intermediate myofilaments are readily seen in all preparations. A few cells showed myofilaments with size and arrangement similar to those of striated muscle. Nexuses are frequently associated with sacs of sarcoplasmic reticulum and are more numerous than in smooth muscles previously studied. In montages of cross-sectioned sphincters about 24 nexuses for 100 muscle cells are counted. Frequently two parts of the same cell are connected by a nexus. Nexuses also occur between muscle cells which are in close relationship with the same nerve varicosity. The density of innervation is very high. In a montage from a full cross-section of the sphincter, there are 2791 profiles of muscle cells and 843 nerve fibres, of which 425 contain synaptic vesicles and 194 are separated from muscle cells by a gap of only about 20 nm. In a number of the closely apposed nerve endings junctional specializations are seen. Collagen fibrils have a diameter of about 50 nm. Some bundles of collagen lie between the muscle cell membrane and the basal lamina. Melanocytes and a few fibroblasts are seen. Blood vessels do not penetrate into the muscle but are numerous around it. No muscle cell is more than 20 µ m away from the nearest capillary. Endothelial cells contain abundant microfilaments 10 nm in diameter. Capillaries are not fenestrated.

CaM kinase II and phospholamban contribute to caffeine-induced relaxation of murine gastric fundus smooth muscle

2005 ◽  
Vol 288 (6) ◽  
pp. C1202-C1210 ◽  
Author(s):  
Minkyung Kim ◽  
Sang Yun Cho ◽  
In Soo Han ◽  
Sang Don Koh ◽  
Brian A. Perrino
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Channel Blocker ◽  
Muscle Tone ◽  
Smooth Muscles ◽  
Cyclopiazonic Acid ◽  
Gastric Fundus ◽  
Cam Kinase Ii ◽  
Cam Kinase ◽  
Camkii Activation

Caffeine has been shown to increase the Ca2+ release frequency (Ca2+ sparks) from the sarcoplasmic reticulum (SR) through ryanodine-sensitive stores and relax gastric fundus smooth muscle. Increased Ca2+ store refilling increases the frequency of Ca2+ release events and store refilling is enhanced by CaM kinase II (CaMKII) phosphorylation of phospholamban (PLB). These findings suggest that transient, localized Ca2+ release events from the SR may activate CaMKII and contribute to relaxation by enhancing store refilling due to PLB Thr17 phosphorylation. To investigate this possibility, we examined the effects of caffeine on CaMKII, muscle tone, and PLB phosphorylation in murine gastric fundus smooth muscle. Caffeine (1 mM) hyperpolarized and relaxed murine gastric fundus smooth muscle and activated CaMKII. Ryanodine, tetracaine, or cyclopiazonic acid each prevented CaMKII activation and significantly inhibited caffeine-induced relaxation. The large-conductance Ca2+-activated K+ channel blocker iberiotoxin, but not apamin, partially inhibited caffeine-induced relaxation. Caffeine-induced CaMKII activation increased PLB Thr17, but not PLB Ser16 phosphorylation. 3-Isobutyl-1-methylxanthine increased PLB Ser16 phosphorylation, but not PLB Thr17 phosphorylation. The CaMKII inhibitor KN-93 inhibited caffeine-induced relaxation and PLB Thr17 phosphorylation. These results show that caffeine-induced CaMKII activation and PLB phosphorylation play a role in the relaxation of gastric fundus smooth muscles.

scholarly journals SARCOPLASMIC RETICULUM AND THE TEMPERATURE-DEPENDENT CONTRACTION OF SMOOTH MUSCLE IN CALCIUM-FREE SOLUTIONS

1971 ◽  
Vol 51 (3) ◽  
pp. 722-741 ◽  
Author(s):  
Andrew P. Somlyo ◽  
Carrick E. Devine ◽  
Avril V. Somlyo ◽  
Stanley R. North
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Extracellular Space ◽  
Room Temperature ◽  
Electromechanical Coupling ◽  
Contractile Response ◽  
Surface Membrane ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Free Cell

The contractile response of turtle oviduct smooth muscle to acetylcholine after 30 min of incubation of muscles in Ca-free, 4 mM ethylene (bis) oxyethylenenitrilotetraacetic acid (EGTA) solutions at room temperature was greater than the contractile response after 30 min of incubation in the Ca-free medium at 37°C. Incubation in Ca-free solution at 37°C before stimulation with acetylcholine in Ca-free solutions at room temperature also reduced the contractile response, suggesting that activator calcium was lost from the fibers at a faster rate at higher temperatures. Electron micrographs of turtle oviduct smooth muscle revealed a sarcoplasmic reticulum (SR) occupying approximately 4% of the nucleus- and mitochondria-free cell volume. Incubation of oviduct smooth muscle with ferritin confirmed that the predominantly longitudinally oriented structures described as the SR did not communicate with the extracellular space. The SR formed fenestrations about the surface vesicles, and formed close contacts (couplings) with the surface membrane and surface vesicles in oviduct and vena caval smooth muscle; it is suggested that these are sites of electromechanical coupling. Calculation of the calcium requirements for smooth muscle contraction suggest that the amount of SR observed in the oviduct smooth muscle could supply the activator calcium for the contractions observed in Ca-free solutions. Incubation of oviduct smooth muscle in hypertonic solutions increased the electron opacity of the fibers. A new feature of some of the surface vesicles observed in oviduct, vena caval, and aortic smooth muscle was the presence of approximately 10 nm striations running approximately parallel to the openings of the vesicles to the extracellular space. Thick, thin, and intermediate filaments were observed in turtle oviduct smooth muscle, although the number of thick filaments seen in the present study appeared less than that previously found in mammalian smooth muscles.

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