In this paper we investigate the effects of caffeine (5-20 mM) on ferret papillary muscle. The intracellular Ca2+ concentration ( [Ca2+]i) was measured from the light emitted by the photoprotein aequorin, which had previously been microinjected into superficial cells. Isometric tension was measured simultaneously. The rapid application of caffeine produced a transient increase of [Ca2+]i, which...

Using double-barreled, Ca2(+)-sensitive microelectrodes, we have examined the characteristics of the Ca2+ release by inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) in the various layers of Xenopus laevis eggs in which the organelles had been stratified by centrifugation. Centrifugation of living eggs stratifies the organelles yet retains them in the normal cytoplasmic milieu. The local increase in...

The Ca2+ indicator photoprotein, aequorin, was used to estimate and monitor intracellular Ca2+ levels in Limulus ventral photoreceptors during procedures designed to affect Na+/Ca2+ exchange. Dark levels of [Ca2+]i were estimated at 0.66 +/- 0.09 microM. Removal of extracellular Na+ caused [Ca2+]i to rise transiently from an estimated 0.5-0.6 microM in a typical cell to approximately 21 microM;...

In A7r5 smooth muscle cells, vasopressin stimulates release of Ca2+ from intracellular stores and Ca2+ entry, and it inhibits adenylyl cyclase (AC) activity. Inhibition of AC is prevented by inhibition of phospholipase C or when the increase in cytosolic [Ca2+] is prevented by the Ca2+ buffer, BAPTA. It is unaffected by pertussis toxin, inhibition of protein kinase C, or L-type Ca2+ channels or...

Apical membrane H+ extrusion in the renal outer medullary collecting duct, inner stripe, is mediated by a Na(+)-independent H+ pump. To examine the regulation of this transporter, cell pH and cell Ca2+ were measured microfluorometrically in in vitro perfused tubules using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein and fura-2, respectively. Apical membrane H+ pump activity, assayed as cell ...

BACKGROUND/AIMS Alzheimer's disease (AD) is known to be related to alterations in neuronal intracellular calcium activity ([Ca2+]i). The present study revealed the distinct role of leptin in Na+/Ca2+-exchanger activity. METHODS [Ca2+]i was determined utilizing Fura-2 fluorescence. The activity of NCX was measured by removal of extracellular Na+ in the presence of external Ca2+. Na+/Ca2+-excha...

ATP-induced calcium (Ca2+) mobilization was investigated in rabbit lens epithelial cells that had been cultured in a medium with pH of 7.4 (group 1), 7.2 (group 2), or 7.0 (group 3) for 10 to 21 d. Intracellular free Ca2+ ([Ca2+]i and pH (pHi) were measured by using fluorescent dyes, fura-2 and BCECF, respectively. The long-term acidification decreased the pHi to 7.15 +/- 0.01, from 7.22 +/- 0....

The intracellular calcium concentration ([Ca2+])i of astrocytes within rat hippocampal slices was measured during simultaneous hypoxia and hypoglycemia to examine the early intracellular signaling events induced by this in vitro model of ischemia. Hypoxia-hypoglycemia for 3.3-7.5 min evoked [Ca2+]i increases in astrocytes iontophoretically loaded with calcium orange (11/14 slices; 2.5 min to pe...

This study was undertaken to investigate possible interrelationships between Ca2+ homeostasis and pH regulation in trout hepatocytes. Exposure of cells to Ca2+ mobilizing agents ionomycin (0.5 micromol l(-1)) and thapsigargin (0.1 micromol l(-1)) induced an increase in intracellular pH (pHi) that was dependent on Ca2+ influx from the extracellular medium as well as Ca2+ release from intracellul...

The mechanisms of Ca(2+)-induced mucin secretion were examined in monolayers of the differentiated epithelial colon cell line C1.16E by combined measurements of free intracellular Ca2+ ([Ca2+]i) using a fluorescence indicator and mucous secretion using a specific and sensitive electrophoretic assay. Carbachol, a cholinergic agonist, induced an initial concentration-dependent [Ca2+]i peak increa...