Expression of GABA(A) receptor alpha3-, theta-, and epsilon-subunit mRNAs during rat CNS development and immunolocalization of the epsilon subunit in developing postnatal spinal cord.

Ionotropic GABA(A) receptors are heteromeric structures composed of a combination of five from at least 16 different subunits. Subunit genes are expressed in distinct cell types at specific times during development. The most abundant native GABA(A) receptors consist of alpha1-, beta2-, and gamma2-subunits that are co-expressed in numerous brain areas.

A gamma 2(R43Q) mutation, linked to epilepsy in humans, alters GABAA receptor assembly and modifies subunit composition on the cell surface.

Genetic defects leading to epilepsy have been identified in gamma2 GABA(A) receptor subunit. A gamma2(R43Q) substitution is linked to childhood absence epilepsy and febrile seizure, and a gamma2(K289M) mutation is associated with generalized epilepsy with febrile seizures plus. To understand the effect of these mutations, surface targeting of GABA(A) receptors was analyzed by subunit-specific immunofluorescent labeling of living cells.

Mitochondrial membrane potential (DeltaPsi) and Ca(2+)-induced differentiation in HaCaT keratinocytes.

We have used the human calcium- and temperature-dependent (HaCaT) keratinocyte cell line to elucidate mechanisms of switching from a proliferating to a differentiating state. When grown in low calcium medium (<0.1 mM) HaCaT cells proliferate.

Potassium channel expression level is dependent on the proliferation state in the GH3 pituitary cell line.

Previously, we showed that the peak density of the transient outward K(+) current (I(to)) expressed in GH3 cells was different in the S phase than in other phases of the cell cycle. Using cell synchronization, we show here that I(to) drops precisely at the quiescent (G(0) phase)/proliferating transition. This change is not due to a modification in the voltage dependence of I(to), but rather to a modification in its inactivation kinetics.

cDNA cloning and expression of a gamma-aminobutyric acid A receptor epsilon-subunit in rat brain.

A cDNA encoding a GABA(A) receptor subunit was isolated from rat brain. The predicted protein is 70% identical to the human epsilon-subunit. It was recently reported [Sinkkonen et al.

Effects of Cl(-) substitution on electrophysiological properties, Ca(2+) influx and prolactin secretion of rat lactotropes in vitro.

In this study, we compared the effects of different chloride (Cl(-)) substitutes - methane sulfonate (CH(3)SO(-)(3)), bromide (Br(-)), nitrate (NO(-)(3)), thiocyanate (SCN(-)) and perchlorate (ClO(-)(4)) - on the secretory activity and calcium current activation of rat lactotropes in primary culture. We observed that CH(3)SO(-)(3) decreased basal prolactin (PRL) secretion. Br(-) had no effect, whereas the more lyotropic anions, such as NO(-3), SCN(-) and C1O(-4), increased basal PRL secretion.

Prolactin induces an inward current through voltage-independent Ca2+ channels in Chinese hamster ovary cells stably expressing prolactin receptor.

There is still only limited understanding of the early steps of prolactin (PRL) signal transduction in target cells. Recent studies have identified some of the essential first steps: these include the rapid association of the PRL receptor with JAK tyrosine kinases and tyrosine phosphorylation of a number of proteins, including members of the signal transducer and activator of transcription (Stats) family. On the other hand, binding of PRL to its receptor is rapidly followed by calcium influx.

Prolactin stimulation of phosphoinositide metabolism in CHO cells stably expressing the PRL receptor.

PRL receptor (PRL-R) activation by PRL triggers a cascade of intracellular events including homodimerization of the receptor, activation of cytoplasmic receptor-associated tyrosine kinase and tyrosine-phosphorylation of various signal transducers. In CHO cells, transfected with the long form of PRL-R, an increase in [Ca2+]i was observed following PRL stimulation whereas Ca2+ is generally coupled with the phosphoinositide metabolism. In this study, we investigated phosphoinositide involvement in the PRL transduction pathway.

Potassium conductance in the androgen-sensitive prostate cancer cell line, LNCaP: involvement in cell proliferation.

Background: Very little is known about the expression of ion channels in prostate cells (both normal and malignant), and their possible role in physiological and pathological functions. We therefore studied ion conductances and their role in the proliferation of LNCaP cells, an androgen-sensitive human prostate cancer cell line.

Methods: We applied patch-clamp recording techniques for electrophysiological studies, and 3H-thymidine incorporation and protein content assays for cell growth studies.

Spontaneous and agonist-induced calcium oscillations in single human nonfunctioning adenoma cells.

The effects of gonadotropin-releasing hormone (GnRH) and GnRH-associated peptide (GAP) on cytosolic free calcium concentration ([Ca(2+)](i)) were investigated in 20 human nonfunctioning pituitary adenomas. We divided these tumors into three classes according to their response pattern to hypothalamic peptides. In type I adenomas (8 out of 20 adenomas), GnRH and GAP mobilized intracellular calcium ions stored in a thapsigargin (TG)-sensitive store.

The Lipidosterolic Extract fromSerenoa repens Interferes with Prolactin Receptor Signal Transduction.

The lipidosterolic extract from the saw palmetto Serenoa repens (LSESr) is commonly used for medical treatment of benign prostatic hypertrophia due to its ability to inhibit 5alpha-reductase which permits the conversion of testosterone to dihydrotestosterone, the active androgen on prostate cell proliferation. However, the complete action mechanism of LSESr is still unknown. Several lines of evidence suggest that, in addition to inhibition of 5alpha-reductase, it may interfere with the action of prolactin (PRL).

Gonadotropin-releasing hormone induced Ca2+ influx in nonsecreting pituitary adenoma cells: role of voltage-dependent Ca2+ channels and protein kinase C.

The action mechanism of gonadotropin-releasing hormone (GnRH) on the cytosolic free calcium concentration ([Ca2+]i) and high-threshold voltage-dependent Ca2+ channel activity was studied in human nonsecreting (NS) pituitary adenoma cells. [Ca2+]i was monitored in individual cells by dual emission microspectrofluorimetry using indo 1 as intracellular fluorescent Ca2+ probe. The whole-cell recording patch-clamp technique was used to study Ca2+ channels.

Thyrotropin-releasing hormone and gonadotropin-releasing hormone-associated peptide modulation of [Ca2+]i in human lactotrophs.

The effect of thyrotropin-releasing hormone (TRH) and gonadotropin-releasing hormone-associated peptide (GAP) was studied on both secretion and intracellular free Ca2+ concentrations ([Ca2+]i) in human pituitary cells cultured from prolactin (PRL)-secreting tumors. Secretion was measured during a 30-min incubation period and we used a microspectrofluorimetric method in individual cells and indo-1 as the fluorescent probe. TRH (10(-8) M) significantly increased PRL release in five out of the six cell populations.

Calcium homeostasis in growth hormone (GH)-secreting adenoma cells: effect of GH-releasing factor.

Human GH-secreting tumors are heterogenous regarding their basal secretory activity and response to GH-releasing factor (GRF). We have investigated whether such different secretory properties could be accounted for by alterations of intracellular mechanisms occurring at the calcium level. Basal free intracellular calcium concentrations ([Ca2+]i) and Ca2+ responses to GRF were studied in single cells cultured from fragments of five GH-secreting pituitary adenomas.

Voltage-dependent calcium current in human decidual cells and its relation to prolactin secretion.

Human decidual cells synthesize and release decidual PRL (dPRL) immunologically and biochemically identical to human pituitary PRL. However, stimulators and inhibitors of PRL secretion such as TRH, bromocriptine or dopamine have no effect on dPRL release. The evidence for the involvement of Ca2+ in dPRL release is based on contradictory or unclear data.