Sarcoplasmic reticulum Ca2+ depletion by caffeine and changes of [Ca2+](i) during refilling in bovine airway smooth muscle cells. 2000

B Bazán-Perkins, and E Sánchez-Guerrero, and V Carbajal, and C Barajas-López, and L M Montaño
Departamento de Investigación en Asma, Instituto Nacional de Enfermedades Respiratorios (INER), Tlalpan #4502, 14080 Mexico City, D.F., Mexico. lmmr@servidor.unam.mx

BACKGROUND In airway smooth muscle (ASM), Ca2+ influx in response to the Ca2+ depletion of the sarcoplasmic reticulum (SR) seems to play a role in the regulation of intracellular free Ca2+ concentrations ([Ca2+](i)). This study evaluates some possible Ca2+ entry pathways activated during SR-Ca2+ depletion induced by 10 mM caffeine. METHODS Enzymatically dispersed bovine ASM cells were loaded with Fura-2/AM to permit measurement of [Ca2+](i) changes in single cells. RESULTS Caffeine (10 mM) induced a transient increase in [[Ca2+](i) that depleted SR-Ca(2)+ content. After caffeine washout, a decrease in basal [Ca2+](i) (undershoot) was invariably observed, followed by a slow recovery. This phenomenon was inhibited by cyclopiazonic acid (5 microM). External Ca(2)+ removal in depolarized and nondepolarized cells induced a decrease in basal [Ca2+](i) that continued until depletion of the SR-Ca2+ content. The decrease in [Ca2+](i) induced by Ca2+-free physiological saline solution (PSS) was accelerated in caffeine-stimulated cells. Recovery from undershoot was not observed in Ca2+-free PSS. Depolarization with KCl and addition of D600 (30 microM) did not modify recovery. Similar results were obtained when the Na(+)/Ca2+ exchanger was blocked by substituting NaCl with KCl in normal PSS (Na(+)-free PSS) or by adding benzamil amiloride (25 microM). CONCLUSIONS SR-Ca2+ content plays an important role in the Ca2+ leak induced by Ca2+-free medium, and does not depend on membrane potential. Additionally, recovery from undershoot after caffeine depends on extracellular Ca2+, and neither voltage-dependent Ca2+ channels nor the Na(+)/Ca2+ exchanger are involved.

UI MeSH Term Description Entries
D007211 Indoles Benzopyrroles with the nitrogen at the number one carbon adjacent to the benzyl portion, in contrast to ISOINDOLES which have the nitrogen away from the six-membered ring.
D007476 Ionophores Chemical agents that increase the permeability of biological or artificial lipid membranes to specific ions. Most ionophores are relatively small organic molecules that act as mobile carriers within membranes or coalesce to form ion permeable channels across membranes. Many are antibiotics, and many act as uncoupling agents by short-circuiting the proton gradient across mitochondrial membranes. Ionophore
D009130 Muscle, Smooth Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed) Muscle, Involuntary,Smooth Muscle,Involuntary Muscle,Involuntary Muscles,Muscles, Involuntary,Muscles, Smooth,Smooth Muscles
D011189 Potassium Chloride A white crystal or crystalline powder used in BUFFERS; FERTILIZERS; and EXPLOSIVES. It can be used to replenish ELECTROLYTES and restore WATER-ELECTROLYTE BALANCE in treating HYPOKALEMIA. Slow-K,Chloride, Potassium
D002110 Caffeine A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine's most notable pharmacological effect is as a central nervous system stimulant, increasing alertness and producing agitation. It also relaxes SMOOTH MUSCLE, stimulates CARDIAC MUSCLE, stimulates DIURESIS, and appears to be useful in the treatment of some types of headache. Several cellular actions of caffeine have been observed, but it is not entirely clear how each contributes to its pharmacological profile. Among the most important are inhibition of cyclic nucleotide PHOSPHODIESTERASES, antagonism of ADENOSINE RECEPTORS, and modulation of intracellular calcium handling. 1,3,7-Trimethylxanthine,Caffedrine,Coffeinum N,Coffeinum Purrum,Dexitac,Durvitan,No Doz,Percoffedrinol N,Percutaféine,Quick-Pep,Vivarin,Quick Pep,QuickPep
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002217 Carbachol A slowly hydrolyzed CHOLINERGIC AGONIST that acts at both MUSCARINIC RECEPTORS and NICOTINIC RECEPTORS. Carbamylcholine,Carbacholine,Carbamann,Carbamoylcholine,Carbastat,Carbocholine,Carboptic,Doryl,Isopto Carbachol,Jestryl,Miostat,Carbachol, Isopto
D002417 Cattle Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor. Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D005711 Gallopamil Coronary vasodilator that is an analog of iproveratril (VERAPAMIL) with one more methoxy group on the benzene ring. Methoxyverapamil,D-600,D600,Elgiprona,Gallobeta,Gallopamil Hydrochloride,Prebet,Procorum,gallopamil von ct,D 600,Hydrochloride, Gallopamil

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