Ca exchange under non-perfusion-limited conditions in rat ventricular cells: identification of subcellular compartments.

Freshly prepared ventricular myocytes from rat hearts, aliquots of which were tested for sarcolemmal integrity by La exposure, were labeled at high 45Ca specific activity. Isotope was subsequently washed out at a perfusion rate of 2.8 ml/s with washout solution sampled each 1 s.

Calcium exchange, structure, and function in cultured adult myocardial cells.

Cells digested from adult rat heart and cultured for 14 days demonstrate all the structural elements, in mature form, associated with the process of excitation-contraction (EC) coupling. The transverase tubular (TT) system is well developed with an extensive junctional sarcoplasmic reticulum (JSR). In nonphosphate-containing buffer contraction of the cells is lost as rapidly as zero extracellular Ca concentration ([Ca]o) solution is applied (less than 10 s) and a negative contraction staircase is produced on increase of stimulation frequency.

Adenylate cyclase, cyclic AMP and IgE-mediated desensitization in rat mast cells.

Rat peritoneal mast cells were desensitized up to 100% with 1-4 additions of suboptimal concentrations of anti-rat IgE over 60-90 min. Desensitized cells rechallenged with anti-IgE showed a 2- to 10-fold increase in cAMP during the initial 1-5 min. Membrane preparations from desensitized cells showed up to a 100-fold rise in cyclase activity following incubation with anti-IgE, compared to a 5- to 10-fold rise in control cells.

Basophil releasability in the newborn: factors limiting immunoglobulin E-mediated histamine release.

Cord basophil preparations from 53 term neonates were studied for various factors affecting immediate hypersensitivity reactions including: basophil IgE receptor density and histamine releasability following incubation with calcium ionophore A23187, zymosan-activated serum (C5a), and anti-IgE. Basophil histamine content (geometric mean, 0.4 pg/basophil, with content in 14/28 cord blood samples below 0.

Reversibility of IgE-mediated rat mast cell desensitization.

Desensitization in normal rat peritoneal mast cells was induced by subthreshold and suboptimal levels of antirat IgE under normal calcium buffer conditions. Low doses of anti-IgE which triggered 0-10% net histamine release, initiated up to 100% desensitization. The rate of desensitization was highly variable in different rats, resulting in an irregular decay of releasability over the first 30 min.