Inhibitors of nitric oxide synthase in human skin.

The aim of this study was to investigate in human skin in vivo the role of nitric oxide in maintaining resting vascular tone, in the vasodilatation caused by local warming and by ultraviolet B light exposure, and in the response to exogenous calcitonin gene-related peptide (CGRP). Cutaneous blood flow was assessed by planimetry of the visible erythema or pallor and by laser Doppler flowmetry. Intradermal injection of the inhibitor of nitric oxide synthase, NG-nitro-L-arginine methyl ester (L-NAME; 25 nmol), into forearm skin produced a visible pallor and a reduction of blood flow at a controlled ambient temperature of 21 degrees C. The control, NG-nitro-D-arginine methyl ester (D-NAME; 25 nmol) or NG-monomethyl-L-arginine (L-NMMA; 25 nmol) did not cause pallor or reduce blood flow. L-NAME and L-NMMA caused dose- and time-dependent increases in pallor, and reductions in cutaneous blood flow in skin that had been locally warmed by immersion in water at 45 degrees C and in skin that had been exposed to ultraviolet B light. D-NAME and D-NMMA at comparable concentrations did not have the effects on skin blood flow observed with the L forms. L-NAME and L-NMMA both inhibited the increased blood flow in human skin caused by the intradermal injection of CGRP (12.5 or 25 pmol). The reduction of CGRP-induced increase of blood flow by L-NAME was reversed by L-arginine. Neither D-NAME nor D-NMMA inhibited the increase in blood flow caused by CGRP. Neither L-NAME nor L-NMMA inhibited the increase in blood flow in human skin caused by the intradermal injection of prostaglandin E2 (63 pmol). The data show that nitric oxide is involved in the maintenance of resting blood flow in human skin and also in the cutaneous vasodilator responses to local warming, ultraviolet B irradiation, or injection of CGRP.

Effects of topical baclofen on C fibre-evoked neuronal activity in the rat dorsal horn.

Baclofen appears to be an agonist for the bicuculline-insensitive gamma-aminobutyrateB receptors associated with C fibre terminals in the dorsal horn of the spinal cord. We have tested the effect of baclofen (applied intrathecally onto the spinal cord) on the A and C fibre-evoked responses of convergent/multireceptive neurones in the halothane-anaesthetized rat. L-Baclofen produced a dose-dependent inhibition of the C fibre- and pinch-evoked activity of these neurones which persisted for 2 h whilst the A fibre and tactile activities were little changed. The C fibre-evoked (X 3 threshold) responses were markedly or completely inhibited 10 min after doses of between 0.25 and 30 micrograms of L-baclofen (n = 21) with 0.05 micrograms causing a 48% (n = 3) and 0.01 micrograms a 28% inhibition (n = 3). D-Baclofen (30 micrograms), the inactive isomer, produced no significant changes in activity (n = 10). Bicuculline (60 micrograms) applied intrathecally before (n = 7) or after (n = 8) L-baclofen did not reverse the inhibitions. Intravenous baclofen (1-3 mg/kg) also produced neuronal inhibitions similar to the effects of intrathecal injection. The results suggest that gamma-aminobutyrateB receptors may exert a presynaptic control of C fibre afferents in the dorsal horn following intrathecal administration in the rat.

IgE-receptor activated chloride uptake in relation to histamine secretion from rat mast cells.

1. Antigen-stimulated histamine secretion from rat peritoneal mast cells was inhibited when extracellular chloride was replaced by either isethionate or gluconate anions, but the histamine release still remained quite substantial. 2. Rat peritoneal mast cells take up 36Cl and the uptake reaches a steady state after 60 min incubation with the isotope. At steady state, the intracellular chloride level in the cells was calculated to be 29 +/- 11.5 mM. 3. The chloride uptake in mast cells was exponential with a rate constant of 0.036 min-1 in resting cells. When the cells were stimulated with antigen, and rate constant for chloride uptake increased to 0.90 min-1: an increase of 25 fold. Under identical experimental conditions histamine release increased 3 fold. 4. The rate of chloride uptake in either resting cells or in antigen-stimulated cells was not changed when the extracellular medium was nominally calcium-free but histamine release was almost completely inhibited in the absence of extracellular calcium. 5. The putative chloride channel blocker DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid) 0.3 to 30 microM, produced a concentration-related inhibition of antigen-stimulated histamine secretion but DIDS (30 microM) did not inhibit the antigen-stimulated increase of chloride uptake. 6. The cyclic AMP analogue, dibutyryl cyclic AMP (1 mM) produced a delayed increase in chloride uptake in resting mast cells but neither dibutyryl cyclic AMP nor 8-bromo cyclic AMP per se induced any histamine secretion. 7. Ouabain (1 mM) which inhibits the Na+/K+ ATPase in rat peritoneal mast cells, failed to affect the uptake of chloride in resting mast cells. 8. The Na/K/2C1-cotransport inhibitor, furosemide (0.7 mM), slowed the unstimulated chloride uptake in resting mast cells and abolished the increased antigen-induced chloride uptake when added together with antigen. In contrast, spontaneous and antigen-induced histamine release were unaffected by the presence of furosemide. However, when furosemide was added to the cell suspension 5 min before stimulation, furosemide was without effect on the antigen-induced chloride uptake.9. In addition to the chloride uptake mediated by chloride channels which may be related to the mechanism of histamine secretion, crosslinking of the high affinity membrane receptors for IgE is followed by a fast chloride uptake that is likely to occur through a furosemide-sensitive Na/K/2C1-cotransporter.

Fc epsilon RI-mediated chloride uptake by rat mast cells: modulation by chloride transport inhibitors in relation to histamine secretion.

1. We have examined the role of extracellular chloride in the mast cell secretion process. The immunologically-directed ligand, antibody to IgE (anti-IgE) required extracellular chloride ions for optimum secretion from rat peritoneal mast cells. In contrast, replacement of extracellular chloride did not alter the mast cell secretory response to compound 48/80, calcium ionophore A23187 or substance P. 2. Anti-IgE-stimulation of mast cells evoked a significant uptake of chloride ions compared to non-stimulated cells. The magnitude of chloride uptake correlated with the magnitude of stimulated histamine secretion. 3. Compound 48/80, substance P and A23187 did not alter the rate of chloride ion uptake, although these agents caused significant histamine secretion. 4. The Na+/K+/2Cl- cotransport inhibitor, furosemide, reduced the rate of anti-IgE-stimulated chloride uptake at a relatively high concentration (700 microM). However, the more potent Na+/K+/2Cl- cotransport inhibitors, bumetanide (100 microM) and piretanide (100 microM) had no effect on the stimulated chloride uptake. 5. Furosemide inhibited anti-IgE-induced histamine secretion, bumetanide potentiated the response and piretanide had no effect. This suggests that their respective action on histamine secretion are unrelated to inhibition of the Na+/K+/2Cl- carrier. 6. The chloride channel blocker, 5-nitro-2-((3-phenylpropyl)-amino)-benzoic acid (NPPB), reduced both anti-IgE-stimulated chloride uptake and the corresponding histamine secretion in a dose-dependent manner. The magnitude of the inhibitory action of the drug on these two cellular processes was comparable, implying that chloride channel activity is related to the mechanism of histamine secretion. 7. It is concluded that chloride uptake has a role in the control of Fc epsilon RI-mediated histamine secretion from rodent mast cells.

The activity of compounds extracted from feverfew on histamine release from rat mast cells.

An extract of the plant feverfew (Tanacetum parthenium) produces a dose-dependent inhibition of histamine release from rat peritoneal mast cells stimulated with anti-IgE or the calcium ionophore A23187. Greater inhibition of anti-IgE-induced histamine release was achieved with feverfew compared with the inhibition of A23187-induced release. Inhibition of anti-IgE-induced histamine release by feverfew extract was observed when the drug was added simultaneously with anti-IgE and the inhibitory activity increased only slightly when the drug was preincubated with the cells for 5 min before anti-IgE stimulation. In this respect feverfew differs from cromoglycate and quercetin. Feverfew extract inhibited anti-IgE-induced histamine release to the same extent in the absence and presence of extracellular glucose. It is concluded that feverfew extract contains a novel type of mast cell inhibitor.

Analyzing current practice patterns: lessons from Amgen's Project ChemoInsight.

PURPOSE/OBJECTIVES: To retrospectively review data on chemotherapy dose/dose intensity in patients with breast cancer. DATA SOURCES: Computerized database, published articles, and book chapter. DATA SYNTHESIS: Chart reviews were conducted of 20,106 patients with breast cancer from 1,135 oncology practices throughout the United States. More dose delays, dose reductions, and suboptimal dose intensity occur in patients who are 65 years of age or older. Overall, dose intensity was not achieved in 18.4% of patients, dose reductions occurred in 25.7% of patients, and dose delays occurred in 43.1% of patients. Neutropenia was often the cause of dose delays/reductions. CONCLUSIONS: A substantial number of patients with breast cancer experience chemotherapy dose delays or reductions. IMPLICATIONS FOR NURSING PRACTICE: Guidelines may help consistently manage primary and secondary prophylaxis of neutropenia. Nurses' can influence patients' attitudes about prescribed therapies.

Comparison of infrared and helium-neon lasers in the measurement of blood flow in human skin by the laser-Doppler technique.

Histamine-induced changes in blood flow in normal human skin were assessed by laser-Doppler velocimetry using 2 lasers of different wavelengths: 780 nm infrared and 633 nm helium-neon. The visible flare response in skin was also measured by planimetry. Laser-Doppler velocimetry was shown to detect both the magnitude of the change in blood flow caused by histamine and also the extent of the changes in the skin. Both parameters were related to the dose of histamine, which ranged between 25 and 750 pmol/site. There was good correlation between the magnitude of the histamine-induced blood flow change and the extent of the response. The flare induced by histamine and measured by planimetry was similar in extent to the blood flow change recorded by laser-Doppler velocimetry. No difference in either the magnitude or the extent of blood flow changes in response to histamine, as measured by laser-Doppler velocimetry, were found when lasers of different wavelengths were used.

Effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on substance P-induced histamine release from rat peritoneal mast cells.

12-O-tetradecanoylphorbol-13-acetate (TPA, 1 to 30 ng/ml) produced a dose-related inhibition of substance P (SP)-induced histamine release from rat peritoneal mast cells. TPA itself induced some histamine release over this concentration range (maximum release about 20% of total). Maximum inhibition of SP-induced release by TPA required preincubation with TPA for at least 10 min. The inhibitory action of TPA was observed in the absence as well as in the presence of extracellular calcium (0.4 mM). Inhibition of diacylglycerol kinase by R 59022 or of diacylglycerol lipase by RHC 80267 reduced SP-induced histamine release. Oleolylacetylglycerol (OAG, 50 microM) inhibited histamine release induced by SP but was less potent than TPA. It is concluded that protein kinase C activation in rat peritoneal mast cells is associated with inhibition of SP-induced histamine release.

Comparison of the histamine-releasing action of substance P on mast cells and basophils from different species and tissues.

The action of the neuropeptide substance P as a histamine-releasing agent has been compared in histamine-containing cells from a variety of different tissues and species. Peritoneal mast cells from rat, mouse and hamster but not human cells gave a concentration-dependent release of histamine in response to substance P. Release was greater in the absence than in the presence of calcium in the extracellular medium. Mast cells from rat mesentery, lung and heart released histamine in response to substance P, but heart mast cells responded only weakly. All guinea-pig mast cells and histamine-containing cells from human tissues did not give any substantial substance-P-induced release of histamine. The data provides further evidence for the functional heterogeneity of histamine-containing cells.

Human basophil degranulation is not triggered by very dilute antiserum against human IgE.

We have attempted to reproduce the findings of Benveniste and co-workers, who reported in 1988 that degranulation of human basophil leukocytes is triggered by very dilute (10(2)-10(120)) antiserum against IgE. The results were contrary to conventional scientific theory and were not satisfactorily explained. Following as closely as possible the methods of the original study, we can find no evidence for any periodic or polynomial change of degranulation as a function of anti-IgE dilution. Our results contain a source of variation for which we cannot account, but no aspect of the data is consistent with the previously published claims.

Substance P and Arg-Pro-Lys-Pro-NH-C12-H25-induced mediator release from different mast cell subtypes of rat and guinea-pig.

Histamine was released from mast cells in isolated perfused heart and kidney of the rat, but not from mast cells in guinea-pig tissues, by a substance P (SP) analogue (SP(1-4)-NH-C12H25), SP(1-4)-C12 for abbreviation. This peptide also released histamine from peritoneal mast cells and basophil leucocytes of the rat. Substance P itself was compared with SP(1-4)-C12 and some structurally related peptides and showed weaker activity. SP(1-4)-C12 also released leukotrienes C4, D4, E4 and thromboxane B2 from rat heart. However, there was little effect on heart rate and force of contraction and no effect on perfusion pressure (vascular resistance) of either rat heart or kidney. The findings demonstrate the structural requirements for histamine release by SP (a possible mediator of 'neurogenic' inflammation), the metabolic energy-dependence of the release process and the functional heterogeneity and interspecies differences in mast cell populations.

Further studies on the actions of endothelin-1 on blood flow in human skin.

When injected into human skin, endothelin-1 produces intense vasoconstriction localized to the site of the injection, but this area of vasoconstriction is surrounded by vasodilatation which spreads several centimetres from the injection site. The vasodilatation induced by intradermal injection of endothelin-1 (63 pmol) into human skin is prevented by local anaesthetic. Pretreatment of human skin with capsaicin also inhibits this response. Pretreatment of subjects with the selective histamine H1-receptor antagonist cetirizine, 10 mg orally 4 h before intradermal injections, inhibited vasodilatation caused by the intradermal injection of histamine (750 pmol), endothelin-1 (63 pmol), and carbachol (750 pmol). Endothelin-1 (0.3-10 microM) and carbachol (1-30 microM) failed to induce histamine release from rat peritoneal mast cells. We conclude that the vasodilatation caused by intradermal injection of endothelin-1 into human skin is neurogenic and is probably mediated by neuropeptide-containing primary afferent neurones. Because neither carbachol nor endothelin-1 cause histamine release from mast cells, our data suggest that histamine release from mast cells at the effector end of the axon reflex is responsible for the carbachol- and endothelin-induced vasodilatation in human skin.

Some studies of the action of betahistine at H1 and H2 receptors for histamine.

Betahistine produced a concentration-dependent contraction of the guinea-pig ileum and was about 27 times less active than histamine in this respect. Betahistine induced desensitization of contractile responses to histamine in the guinea-pig ileum. The H1 histamine receptor antagonist mepyramine was a competitive antagonist of the action of betahistine on the guinea-pig ileum. Betahistine caused relaxation of the rat uterus contracted by acetylcholine, and this action of betahistine was blocked by the H2 receptor antagonist cimetidine. Betahistine had a concentration-dependent positive chronotropic action on isolated guinea-pig atria, and in this respect was tenfold less potent than histamine. The action of betahistine on the atria was blocked by the H2 receptor antagonist YM11170. Betahistine caused a concentration-related contraction of the isolated lung parenchymal strip of the guinea-pig, and YM11170 potentiated this effect. Betahistine failed to release histamine from rat peritoneal mast cells at concentrations up to 100 microM and it did not prevent histamine release induced by either substance P or anti-IgE. Betahistine produced a dose-related flare and wheal reaction when injected intradermally into human skin. It is concluded that betahistine has agonist activity at both H1 and H2 receptors for histamine.