Effects of noradrenaline on membrane currents and action potential shape in smooth muscle cells from guinea-pig ureter.

1. The effects of noradrenaline (NA) on action potential shape and underlying membrane currents were examined in single smooth muscle cells freshly isolated from the ureter of the guinea-pig. 2.

Receptor for catecholamines responding to catechol which potentiates voltage-dependent calcium current in single cells from guinea-pig taenia caeci.

1. Single isolated cells were obtained from the taenia of the guinea-pig's caecum by enzymic digestion and held under voltage clamp. The effects of various catecholamines, sympathomimetics and related compounds were tested for their ability to potentiate the voltage-dependent calcium current (ICa) evoked in these cells by a depolarizing step.

Tetrahexylammonium ions increase Ca2+ sensitivity of contraction of guinea-pig ileal smooth muscle.

Effects of tetraalkylammonium ions, having tetraalkyl chains of increasing length from ethyl to octyl, on inositol-trisphosphate (InsP3)-induced Ca2+ release and contractile mechanics were examined in guinea-pig skinned ileal smooth muscle longitudinal strips. Although tetrahexylammonium ions (THexA) appeared to be the most potent inhibitor of Ca2+ release among the tetraalkylammonium ions examined, an additional and more prominent effect was found, i.e.

Enhanced expression of neurotensin/neuromedin N mRNA and products of NT/NMN precursor processing in neonatal rats.

Intestinal levels of immunoreactive neurotensin (iNT) and neuromedin N (iNMN), as well as mRNA for the NT/NMN precursor, were elevated during the suckling period in rats. While transient expression of NT/NMN was observed at 1-5 days of age in the proximal small intestine and colon, NT/NMN levels in the ileum increased to peak at 10-20 days of age and then decreased to adult levels. The levels of these peptides were not elevated in the central nervous system and pituitary over this time period.

Effect of isoprenaline on Ca2+ channel current in single smooth muscle cells isolated from taenia of the guinea-pig caecum.

1. The effects of isoprenaline (Iso) on Ca2+ channel current in enzymatically isolated single cells of the guinea-pig taenia caeci were examined using the standard whole-cell voltage-clamp method. 2.

[Physiological functions and regulation of K+ and Cl- channels in single smooth muscle cells].

The major functional roles of K channels in smooth muscle cells are as follows: (i) Keeping resting membrane potential (RMP). (ii) Induction of hyperpolarization (HP) in response to bioactive substances. (iii) Facilitation of action potential repolarization (APR).

Cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum Ca(2+)-pump, reduces Ca(2+)-dependent K+ currents in guinea-pig smooth muscle cells.

1. Effects of cyclopiazonic acid (CPA), a specific inhibitor of the Ca(2+)-ATPase in sarcoplasmic reticulum (SR), on membrane ionic currents were examined in single smooth muscle cells freshly isolated from ileal longitudinal strips and urinary bladder of the guinea-pig. 2.

Ca-dependent K channels in smooth muscle cells permeabilized by beta-escin recorded using the cell-attached patch-clamp technique.

Using the cell-attached patch-clamp technique, the activity of single, Ca-dependent K channels was recorded in single smooth muscle cells permeabilized by beta-escin. The conductance and the relationship between the open probability of the channels and pCa recorded in permeabilized cells were very similar to those obtained in excised inside-out patches. At pCa 7, application of 30 microM acetylcholine (ACh) or 0.

Sodium currents in smooth muscle cells freshly isolated from stomach fundus of the rat and ureter of the guinea-pig.

1. Inward currents elicited by depolarization from holding potentials of -80 to -10 mV in single smooth muscle cells isolated from stomach fundus of the rat and ureter of the guinea-pig had two components. The initial fast component (Ifi) was activated and mostly inactivated within 1-2 and 10 ms, respectively, at 21 degrees C.

Neurotensin elevates hematocrit and plasma levels of the leukotrienes, LTB4, LTC4, LTD4 and LTE4, in anesthetized rats.

The IV injection of neurotensin (NT) into anesthetized rats produced a marked increase in hematocrit, labored breathing and peripheral blood stasis with cyanosis. This effect could also be produced by the NT-related peptides, neuromedin-N and xenopsin; however, it was not observed when nine other biologically active peptides, including bradykinin and substance P, were tested. Associated with these responses were increases in the plasma levels of histamine (measured radioenzymatically) and the leukotrienes, LTB4, LTC4, LTD4, and LTE4 (measured by RIA and HPLC).

Xenopsin-related peptide(s) are formed from xenopsin precursor by leukocyte protease(s) and cathepsin D.

Lysates of isolated rat polymorphonuclear leukocytes and macrophages were found to generate xenopsin-related peptides when incubated with a liver extract used as a source of precursor. The lysosomal enzyme, cathepsin D, was also shown to display this property and to share with the lysate a similar pH dependence (optimum, approximately pH 3.5) and sensitivity to the acid protease inhibitor, pepstatin A (ID50: lysate, 10 nM; cathepsin D, 30 nM).

Mechanisms of NE-induced reduction of Ca current in single smooth muscle cells from guinea pig vas deferens.

Effects of norepinephrine (NE) on voltage-dependent Ca channel current (ICa) were examined applying whole cell patch-clamp technique to single smooth muscle cells freshly isolated from vas deferens of the guinea pig. K currents and contraction of the cell were abolished by Cs and EGTA in the pipette solution, respectively. The peak ICa and Ba current (IBa) elicited by depolarization from -60 mV in a solution containing 2.

Characteristics of transient outward currents in single smooth muscle cells from the ureter of the guinea-pig.

1. Two kinds of transient outward currents were observed upon depolarization of single smooth muscle cells isolated from guinea-pig ureter. The major transient outward current was through Ca2(+)-activated K+ channels (IK(Ca) which had a large conductance (130 pS; 126 mM [K+]i/5.

Isolation and structures of xenopsin-related peptides from rat stomach, liver and brain.

Using radioimmunoassay for detection, a mammalian counterpart to amphibian xenopsin (XP) was isolated and sequenced from pepsin-treated extracts of three different rat tissues and shown to be H-Phe-His-Pro-Lys-Arg-Pro-Trp-Ile-Leu-OH. This peptide, which shares six of the eight residues in XP, existed primarily in large molecular form(s) in the rat from which it could be liberated by the enzyme, pepsin. The XP-related sequence was differentially distributed through tissues, with concentrations ranging from ca.

Effects of tetraethylammonium and 4-aminopyridine on outward currents and excitability in canine tracheal smooth muscle cells.

1. The effects of tetraethylammonium (TEA) and 4-aminopyridine (4-AP) on membrane currents and on single channel K currents in smooth muscle cells isolated from canine trachea were examined by use of tight seal whole cell- and patch-clamp techniques. 2.

Canine neurotensin, neurotensin6-13 and neuromedin N: primary structures and receptor activity.

Canine neurotensin (NT) and neuromedin N (NMN) were isolated from extracts of ileal mucosa using radioimmunoassay for detection. The structures determined were consistent with those predicted by earlier cDNA work. The molar ratio of NT to NMN was ca.

Exocrine secretion and processing of pro-xenopsin in rat gastric lumen.

This study examines the effects of acid, acid secretagogues, and pepstatin on gastric luminal concentrations of xenopsin-like immunoreactivity (XPLI) by in situ luminal perfusion of the stomach in anesthetized rats. During perfusion with saline over a 2-h period, the concentration of XPLI fell in parallel with acid output. Levels of XPLI fell more rapidly when the saline contained 20 micrograms/ml pepstatin A and when phosphate-buffered saline (pH 7.

Ionic currents in single smooth muscle cells from the ureter of the guinea-pig.

1. Ionic currents underlying the action potential were recorded from enzymatically isolated smooth muscle cells of guinea-pig ureter. 2.

Measurement and simulation of noninactivating Ca current in smooth muscle cells.

An attempt was made to obtain electrophysiological evidence for continuous influx of Ca ion through voltage-dependent Ca channel (VDCC) in smooth muscle during long depolarization, for example in high K solution. Noninactivated Ca current [ICa(ni)] remaining after the accomplishment of voltage-dependent inactivation by prolonged depolarization for approximately 1 min was detected by three means under whole cell voltage clamp in several types of smooth muscle cells. The measurement of ICa(ni) was performed by micropuff application of Cd2+ or Ca2+ in the presence or absence of 5 mM extracellular Ca, respectively, or jump of extracellular Ca concentration [( Ca]o).

Influence of diet on the development of antral gastrin-like immunoreactivity in the stomach of rats.

The effects of individual food constituents on antral gastrin-like immunoreactivity concentrations were studied in young rats. Rats aged 7 to 20 days were given only rat breast milk and then weaned by various nutrients (regular laboratory chow, protein (ovalbumin)-, fat- or carbohydrate (starch)-rich food). Rats receiving rat breast milk only until 27 days of age were also studied.

Neurotensin receptors on the rat liver plasma membranes.

Neurotensin (NT) is now classified as a brain-gut peptide in the central nervous system and gastrointestinal tract. In the present study, we characterized the NT receptors on the rat liver plasma membranes. The specific binding of [3H]NT was time dependent, reversible, and saturable.