Using the patch-clamp technique, we have identified two types of Ca(2+)-activated K+ (K(Ca)) channels in the human leukemic T cell line. Jurkat. Substances that elevate the intracellular Ca2+ concentration ([Ca2+]i), such as ionomycin or the mitogenic lectin phytohemagglutinin (PHA), as well as whole-cell dialysis with pipette solutions containing elevated [Ca2+]i, activate a voltage-independen...

A tight balance between synaptic vesicle exocytosis and endocytosis is fundamental to maintaining synaptic structure and function. Calcium influx through voltage-gated Ca2+ channels is crucial in regulating synaptic vesicle exocytosis. However, much less is known about how Ca2+ regulates vesicle endocytosis or how the endocytic machinery becomes enriched at the nerve terminal. We report here a ...

Canine cardiac Purkinje cells contain both L- and T-type calcium currents, yet the single Ca2+ channels have not been characterized from these cells. Additionally, previous studies have shown an overlap between the steady-state inactivation and activations curves for L-type Ca2+ currents, suggesting the presence of L-type Ca2+ "window" current. We used the on-cell, patch-clamp technique to stud...

The major pathological correlate of cerebral palsy is ischemic injury of CNS white matter. Histological studies show early injury of glial cells and axons. To investigate glial cell injury, I monitored intracellular Ca2+ and cell viability in fura-2-loaded neonatal rat white matter glial cells during ischemia. Fura-2 fixation combined with immunohistochemistry revealed that fura-2-loaded cells ...

Sensory transduction in vertebrate photoreceptors and olfactory sensory neurons is mediated by cyclic nucleotide-gated (CNG) channels that conduct mono- and divalent cations. Ca2+ entering the cell through CNG channels intimately controls signaling pathways by regulating several key enzymes. Cloned CNG channels from photoreceptors and olfactory sensory neurons profoundly differ in their relativ...

Large conductance K+ (BK) channels are expressed widely in neurons, where their activation is regulated by membrane depolarization and intracellular Ca2+ (Ca2+i). To enable this regulation, BK channels functionally couple to both voltage-gated Ca2+ channels (VGCCs) and channels mediating Ca2+ release from intracellular stores. However, the relationship between BK channels and their specific Ca2...

Thyrotropin-releasing hormone (TRH) stimulates pituitary secretion by steps involving a cytosolic Ca2+ rise. We examined various pathways of Ca2+ elevation in pituitary GH3 cells. By using the patch clamp technique in the whole-cell configuration and Ba2+ as divalent charge carrier through Ca2+ channels, TRH (1 microM) reversibly reduced the current by about 55%. This hormonal effect was preven...

The properties of the K+ pathway underlying regulatory volume decrease (RVD) in human blood lymphocytes were investigated. Evidence is presented for the existence of three types of K+ conductance in these cells. Ionomycin, a Ca2+ ionophore, induced a K(+)-dependent hyperpolarization, indicating the presence of Ca2(+)-activated K+ channels, which were blocked by charybdotoxin (CTX). CTX also ind...

One of the fastest cellular responses following activation of epidermal growth factor receptor is an increase in intracellular Ca2+ concentration. This event is attributed to a transient Ca2+ release from internal stores and Ca2+ entry from extracellular compartment. Store-operated Ca2+ channels are defined the channels activated in response to store depletion. In the present study, we determin...

The dihydropyridine Ca2+ antagonist drugs used in the therapy of cardiovacular disorders inhibit L-type Ca2+ channels by binding to a single high affinity site. Photoaffinity labeling and analysis of mutant Ca2+ channels implicate the IIIS6 and IVS6 segments in high affinity binding. The amino acid residues that are required for high affinity binding of dihydropyridine Ca2+ channel antagonists ...