Ca(2+) channel inactivation in the neurons of the freshwater snail, Lymnaea stagnalis, was studied using patch-clamp techniques. In the presence of a high concentration of intracellular Ca(2+) buffer (5 mM EGTA), the inactivation of these Ca(2+) channels is entirely voltage dependent; it is not influenced by the identity of the permeant divalent ions or the amount of extracellular Ca(2+) influx...

This study asks whether arterial blood ionized calcium concentration (Ca++) can regulate the serum level of 1,25-dihydroxy-vitamin D3 [1,25(OH)2D3] independently of serum phosphorus and parathyroid hormone (PTH). We infused either PTH (bovine 1-34, 10 U/kg body wt/h) or saline into awake and unrestrained rats for 24 h, through a chronic indwelling catheter. PTH raised total serum calcium and ar...

The ionized concentration of calcium in physiological buffers ([Ca(2+)]) is normally calculated using either tabulated constants or software programs. To investigate the accuracy of such calculations, the [Ca(2+)] in EGTA [ethylene glycol-bis(β-aminoethylether)-N,N,N|,N|-tetraacetic acid], BAPTA [1,2-bis(o-aminophenoxy) ethane-N,N,N|,N|-tetraacetic acid], HEDTA [N-(2-hydroxyethyl)-ethylenediami...

IL-8, a potent neutrophil chemoattractant that is elevated about 200-fold in exudative neutrophils isolated from localized inflammatory sites in vivo, is thought to play a major role in recruitment of neutrophils to inflammatory sites. Incubation of peripheral blood neutrophils with thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-sequestering-ATPase, causes a dose-dependent inducti...

1. The effects of external Ca2+, EGTA, ionophore A23187, CN-, dinitrophenol and iodoacetamide on the rate of protein degradation in the rat diaphragm and epitrochlearis muscles in vitro were investigated. 2. External Ca2+ increased protein degradation when compared with external EGTA. Protein degradation was further increased by Ca2+ + ionophore A23187. 3. EGTA and ionophore A23187 decreased AT...

Porcine heart was observed to express annexins V (CaBP33) and VI in large amounts, and annexins III and IV in much smaller amounts. Annexin V (CaBP33) in porcine heart was examined in detail by immunochemistry. Homogenization and further processing of heart in the presence of EGTA resulted in the recovery of annexin V (CaBP33) in the cytosolic fraction and in an EGTA-resistant, Triton X-100-sol...

Plasma membranes of P815 mastocytoma cells contain a set of proteins that remain selectively insoluble upon extraction of the membranes with Triton X-100, and appear to form a membrane skeletal matrix independent of the filamentous cytoskeletal systems. EGTA treatment of the matrix was found to release approximately 25% of the protein as polypeptides of 70, 69, 38, and 36 kD, all of which appea...

Eggs from the sea urchin, Lytechinus pictus, were injected with either EGTA or EDTA, and were subsequently fertilized. EGTA prevented cortical vesicle discharge and formation of the fertilization membrane. EDTA had either no effect, or sometimes retarded the elevation of the fertilization membrane, or reduced the percentage of eggs with elevated membranes. Theoretical considerations lead to est...

We evaluated the influence of hemolysis on total serum calcium as determined with the Du Pont aca, SMA 12/60, Ektachem 400, Corning 940 EGTA titrator, and the Beckman Astra 8, comparing results with those obtained by atomic absorption spectroscopy. We find that hemoglobin does not influence calcium measurements with the SMA 12/60, Ektachem 400, or Beckman Astra 8. The presence of hemoglobin exc...

Incubation of purified rat brain Ca2+/calmodulin-dependent protein kinase II for 2 min in the presence of Ca2+, calmodulin (CaM), Mg2+, and ATP converted the kinase from a completely Ca2+-dependent kinase to a substantially Ca2+-independent form with little loss of total activity. Subsequent addition of EGTA to the autophosphorylation reaction enhanced further autophosphorylation of the kinase ...