Effects of vasopressin on the sympathetic contraction of rabbit ear artery during cooling

In order to analyse the effects of arginine-vasopressin on the vascular contraction to sympathetic nerve stimulation during cooling, the isometric response of isolated, 2-mm segments of the rabbit central ear (cutaneous) artery to electrical field stimulation (1-8 Hz) was recorded at 37 and 30 degrees C. Electrical stimulation (37 degrees C) produced frequency-dependent arterial contraction, which was reduced at 30 degrees C and potentiated by vasopressin (10 pM, 100 pM and 1 nM). This potentiation was greater at 30 than at 37 degrees C and was abolished at both temperatures by the antagonist of vasopressin V1 receptors d(CH2)5 Tyr(Me)AVP (100 nM). Desmopressin (1 microM) did not affect the response to electrical stimulation. At 37 degrees C, the vasopressin-induced potentiation was abolished by the purinoceptor antagonist PPADS (30 microM), increased by phentolamine (1 microM) or prazosin (1 microM) and not modified by yohimbine (1 microM), whilst at 30 degrees C, the potentiation was reduced by phentolamine, yohimbine or PPADS, and was not modified by prazosin. The Ca2+-channel blockers, verapamil (10 microM) and NiCl2 (1 mM), abolished the potentiating effects of vasopressin at 37 degrees C whilst verapamil reduced and NiCl2 abolished this potentiation at 30 degrees C. The inhibitor of nitric oxide synthesis, L-NOARG (100 microM), or endothelium removal did not modify the potentiation by vasopressin at 37 and 30 degrees C. Vasopressin also increased the arterial contraction to the alpha2-adrenoceptor agonist BHT-920 (10 microM) and to ATP (2 mM) at 30 and 37 degrees C, but it did not modify the contraction to noradrenaline (1 microM) at either temperature. These results suggest that in cutaneous (ear) arteries, vasopressin potentiaties sympathetic vasoconstriction to a greater extent at 30 than at 37 degrees C by activating vasopressin V1 receptors and Ca2+ channels at both temperatures. At 37 degrees C, the potentiation appears related to activation of the purinoceptor component and, at 30 degrees C, to activation of both purinoceptor and alpha2-adrenoceptor components of the sympathetic response.

Adrenergic reactivity after inhibition of nitric oxide synthesis in the cerebral circulation of awake goats

The interaction between nitric oxide (NO) and adrenergic reactivity in the cerebral circulation was studied using in vivo and in vitro preparations. Blood flow to one brain hemisphere (cerebral blood flow) was electromagnetically measured in conscious goats, and the effects of norepinephrine, tyramine and cervical sympathetic nerve stimulation were recorded before (control) and after inhibition of NO formation with Nw-nitro-l-arginine methyl ester (l-NAME). The responses to norepinephrine, tyramine and electrical field stimulation were also recorded in segments, 4 mm in length, from the goat's middle cerebral artery under control conditions and after l-NAME. In vivo, l-NAME (10 goats, 47 mg kg-1 administered i.v.) reduced resting cerebral blood flow by 37+/-2%, increased mean systemic arterial pressure by 24+/-3%, reduced heart rate by 35+/-2%, and decreased cerebrovascular conductance by 52+/-2% (all P<0.01). Norepinephrine (0.3-9 microgram), tyramine (50-500 microgram), and supramaximal electrical sympathetic cervical nerve stimulation (1. 5-6 Hz) decreased cerebrovascular conductance, and these decreases were significantly higher after l-NAME than under control conditions, remaining higher for about 48 h after this treatment. Norepinephrine (10-8-10-3 M), tyramine (10-6-10-3 M) and electrical field stimulation (1.5-6 Hz) contracted isolated cerebral arteries, and the maximal contraction, but not the sensitivity, was significantly higher in the arteries treated than in non-treated with l-NAME (10-4 M). Therefore, the reactivity of cerebral vasculature to exogenous and endogenous norepinephrine may be increased after inhibition of NO synthesis. This increase might be related, at least in part, to changes at postjunctional level in the adrenergic innervation of the vessel wall, and it might contribute to the observed decreases in resting cerebral blood flow after inhibition of NO synthesis.

Expression of ICAM-1 and HLA-DR by human conjunctival epithelial cultured cells and modulation by nedocromil sodium

It is unclear whether conjunctival epithelial cells participate in the development of immune-mediated events. Using a previously reported in vitro system of human conjunctival epithelium, we determined whether conjunctival epithelial cells express two relevant markers in the antigenic presentation process. Moreover, the potential capability of nedocromil sodium, an antiallergic and antiinflammatory drug, to modulate such expression was investigated. Primary cultures of human conjunctival epithelium and Chang conjunctival cells, incubated with or without 100 U/ml IL-1beta and/or IFNgamma for 1, 3 or 6 h, were simultaneously exposed to 10(-5) M nedocromil sodium. The expression of the intercellular adhesion molecule-1 (ICAM-1) and the human leukocyte antigen-DR (HLA-DR) was determined immunocytochemically. Constitutive expression of ICAM-1 and HLA-DR was observed in primary cultures and Chang cells and was minimally affected by incubation with IL-1beta and/or IFNgamma. The addition of nedocromil sodium resulted in complete abolition of HLA-DR expression and a notable reduction in ICAM-1 expression in primary cultures and Chang cells. These results suggest that epithelial cells from human conjunctiva constitutively express ICAM-1 and HLA-DR in vitro and that such expression is downregulated by nedocromil sodium. This may indicate that conjunctival epithelial cells may be another target for this drug.

Effects of hyperthermia on contraction and dilatation of rabbit femoral arteries

To analyze the effect of hyperthermia on the vascular response, the isometric response of isolated rabbit femoral artery segments was recorded at 37 degreesC and hyperthermia (41 and 44 degreesC). Contraction to potassium (5 x 10(-3)-5 x 10(-2) M) was significantly greater at 41 and 44 than at 37 degreesC and increased by inhibition of nitric oxide (NO) synthesis with Nomega-nitro-L-arginine (L-NNA; 10(-4) M) or endothelium removal at 37 degreesC but not at 41 or 44 degreesC. Norepinephrine (10(-9)-10(-4) M) produced a concentration-dependent contraction greater at 41 or 44 than at 37 degreesC and not modified by endothelium removal or L-NNA at either temperature. Phenylephrine (10(-9)-10(-4) M) produced a contraction increased by warming to 44 degreesC but not to 41 degreesC. The specific alpha2-adrenoceptor agonist BHT-920 produced a weak contraction, reduced by the alpha1-adrenoceptor antagonist prazosin (10(-6) M) and increased at 44 degreesC but not at 41 degreesC. The concentration-dependent contraction to endothelin-1 (ET-1; 10(-11)-10(-7) M) was increased by warming to 41 and 44 degreesC and by endothelium removal or L-NNA at 37 degreesC but not at 41 or 44 degreesC. Response to ET-1 was reduced by endothelin ETA-receptor antagonist BQ-123 (10(-5) M) and ETB-receptor antagonist BQ-788 (10(-5) M). In arteries precontracted with ET-1 (10(-8)-3 x 10(-8) M), relaxation to sodium nitroprusside (10(-8)-10(-4) M) was increased at 41 and 44 degreesC vs. at 37 degreesC, but that of ACh (10(-8)-10(-4) M) or adenosine (10(-8)-10(-4) M) was not different at all temperatures studied. Relaxation to ACh, but not adenosine, was reduced similarly by L-NNA at all temperatures studied. These results suggest hyperthermia in muscular arteries may inhibit production of, and increase dilatation to, NO, resulting in unchanged relaxation to ACh and increased constriction to KCl and ET-1, and may increase constriction to stimulation of alpha1-adrenoceptors by NO-independent mechanisms.

Severe experimental uraemia does not decrease the population of rat pituitary somatotrophs

BACKGROUND

Growth hormone (GH) secretion by the anterior pituitary has been shown to be depressed in severely uraemic rats. Changes in the population of pituitary somatotrophs might be partially responsible for this decrease.

METHODS

To analyse the population of pituitary somatotrophs in severe uraemia, immunocytochemical detection and quantification of GH-producing cells were carried out on paraffin sections from young rats either 5/6 nephrectomized, sham-operated fed ad libitum or sham-operated pair-fed with the nephrectomized animals.

RESULTS

Nephrectomized rats were severely uraemic and growth retarded. The overall cell density (total pituitary cells/mm2) was higher in 5/6 nephrectomized animals in comparison with the two sham-operated groups. Thus, although the percentage of GH cells was slightly lower in nephrectomized than in control rats, no difference in either the density (cells/mm2) or the cross-sectional area of GH cells was found among groups.

CONCLUSIONS

These results suggest that severe experimental uraemia interferes with the maturation process of the pituitary gland and support the contention that differences in either the number or the size of pituitary somatotrophs cannot explain the reduced GH secretion previously reported in severely uraemic rats.

Influence of two commercial fibers in the pharmacokinetics of ethinylestradiol in rabbits

Fiber formulations are used in human nutrition owing to their beneficial properties for health. It is probable that ingestion of fiber coincides with the oral administration of drugs, and a modification of its oral absorption, and therefore of its pharmacokinetics, can appear. In the present study, the compartmental and noncompartmental pharmacokinetic parameters of ethinylestradiol (EE) in rabbits after oral administration were determined. It was also studied whether the presence of two different fiber formulations [A, wheat bran (76.5%), fruit fiber (12%) and guar gum (2%) and B, Plantago ovata seeds (65%) and P. ovata seed cuticles (2.2%)] in the gastrointestinal tract modified the pharmacokinetics of EE when administered at the same time. Three groups of rabbits were used: control, fiber A and fiber B. The animals in all three groups received 1 mg/kg b. wt. EE. The estrogen was administered alone in the control group and in the presence of 4 g of fiber A and fiber B, respectively, in the other two groups. After compartmental (two-compartment open model) and noncompartmental analyses of plasma concentrations, statistical analysis revealed that the presence of fiber (both A and B) decreased between 29% and 35% the extent of EE absorbed (represented by the pharmacokinetic parameters area under the curve and the maximum plasma concentration) without affecting the rate of the absorption process (represented by the time to reach maximum concentration and the absorption rate constant).

Organochlorine pesticide residues in muscle tissue of rainbow trout, Oncorhynchus mykiss, taken from four fish farms in León, Spain

Levels of nine organochlorine pesticides (lindane, heptachlor epoxide, aldrin, dieldrin, endrin, o,p'-TDE, p,p'-TDE, p,p'-DDE and p,p'-DDT) were determined in muscle samples of rainbow trout, Onchorhynchus mykiss, collected from four fish farms in the province of León, in the north-west of Spain (Europe). The highest incidence percentage was for lindane (67.5%) and heptachlor epoxide (55.0%). Organochlorine residue levels detected contributed slightly to acceptable daily intakes (ADIs) established by the Food and Agriculture Organization of the United Nations and the World Health Organization (lindane 0.22-2.3%; sigma DDT 0.05-0.46%; heptachlor epoxide 10.0-71.4% and sigma dieldrin 16.7-33.3% assuming 300 g of trout muscle as a mean daily intake). The highest concentration found was for heptachlor epoxide (0.043 microgram/g).

PCA50941, a new 1,4-dihydropyridine, reverses endothelin-induced cardiogenic shock in the anesthetized goat

This study was designed to test the hypothesis that the properties of novel 1,4-dihydropyridine PCA50941 could favor the recovery of cardiogenic shock. Coronary blood flow (CBF), measured with an electromagnetic flow probe placed on the left circumflex coronary artery, systemic arterial pressure and heart rate were recorded in 24 anesthetized goats; left ventricular pressure and dP/dt were also recorded in 19 of these goats. Under control conditions, intracoronary injections in 5 goats of PCA50941 (10-120 microg) caused smaller reductions of CBF than those of Bay K 8644 (0.3-10 microg) (the reduction of CBF by 120 microg PCA50941 was 25% and that by 10 microg Bay K 8644 was 43%), and i.v. infusions in 4 goats of PCA50941 (10-300 microg/min) did not modify CBF nor the other hemodynamic variables recorded, whereas i.v infusion of Bay K 8644 (10-30 microg/min) reduced CBF by 20% and increased arterial pressure, left ventricular pressure and dP/dt. During control conditions and endothelin-induced cardiogenic shock, respectively, the values for 15 goats were: for CBF, 33+/-4 vs. 16+/-4 ml/min; for mean arterial pressure, 88+/-4 vs. 60+/-5 mm Hg; for left ventricular systolic pressure, 102+/-5 vs. 75+/-4 mm Hg; for dP/dt, 1453+/-147 vs. 925+/-101 mm Hg/s (all P<0.05), and for heart rate, 77+/-6 vs. 81+/-6 beats/min (P>0.05). Intravenous infusion of PCA50941 (100 microg/min) reversed the hemodynamic variables from the shock state to control values within 20 min in 5 of 6 animals, whereas i.v. administration of Bay K 8644 (10-30 microg/min) was not effective in 4 of 5 animals, and the vehicle (DMSO) was not effective in none of 4 animals in reversing the hemodynamic shock state. Therefore, it is suggested that PCA50941, a novel 1,4-dihydropyridine, has a cardiovascular profile that might be suitable for treating cardiogenic shock states.

[Changes of the complement system in myelodysplastic syndromes]

PURPOSE

To search complement system activity and detection of circulating immune complexes in a group of patients with myelodysplastic syndromes (MDS) classified as with relatively favourable and unfavourable prognosis.

PATIENTS AND METHODS

28 patients with MDS were examined, 12 with refractory anaemia and 4 with refractory ringed sideroblastic anaemia, both subgroups of relatively favourable prognosis; 9 patients with refractory anaemia with blastic excess and 3 with refractory anaemia with blastic excess in transformation, subgroups of unfavourable prognosis. We determined factor B, alternate and classical hemolytic activity, as well as C3 and C4 quantification of the complement system. Circulating immune complexes detection was performed by the C1q deviation test and polyethylene glycol 6000 precipitation method at 3.75% final concentration.

RESULTS

A significant decrease in C3 level, alternate haemolytic activity and factor B was demonstrated in the unfavourable prognosis subgroups in comparison with patients of favourable prognosis and normal controls.

CONCLUSIONS

Our results suggest the possibility of subclinical infections in patients with unfavourable prognosis.

In vivo and in vitro action of endothelin-1 on goat cerebrovascular bed

This study concerned the effects and mechanisms of action of endothelin-1 on the cerebral circulation. Cerebral blood flow was electromagnetically measured in awake goats. Endothelin-1 (0.01-0.3 nmol) produced dose-dependent decreases in this flow (maximal reduction = 34%) and increases in cerebrovascular resistance (maximal increase = 74%) (P < 0.01). IRL 1620 (Suc-[Glu9, Ala11,15]endothelin-1-(8-21), agonist for endothelin ET(B) receptors, 0.01-0.3 nmol) slightly decreased cerebral blood flow. The effects of endothelin-1, but not those of IRL 1620, on cerebral blood flow were diminished by 50% during infusion of the antagonist for endothelin ET(A) receptors, BQ-123 (cyclo-(D-Asp-Pro-D-Val-Leu-Trp), 2 nmol min(-1)), but not affected during infusion of the antagonist for endothelin ET(B) receptors, BQ-788 (N-[N-[N-[(2,6-dimethyl-1-piperidinyl)carbonyl]-4-methyl-L-Leucyl-1-(met hoxycarbonyl)-D-tryptophyl]-Dnorleucine monosodium), 2 nmol min(-1)). Intravenous administration of NW-nitro-L-arginine methyl ester (L-NAME, 47 mg kg(-1)) or NW-nitro-L-arginine (L-NNA, 47 mg kg(-1)) reduced basal cerebral blood flow by 39 and 33%, increased cerebrovascular resistance by 108 and 98% and mean arterial pressure by 23 and 17%, and decreased heart rate by 27 and 25%, respectively (all at least P < 0.05). The increases in cerebrovascular resistance (as absolute values) induced by endothelin-1 were not affected during either L-NAME or L-NNA (as absolute values and percentages). Intravenous administration of meclofenamate (5 mg kg(-1)) did not change the cerebrovascular effects of endothelin-1 and IRL 1620. In isolated goat cerebral arteries under control, resting conditions, endothelin-1 (10(-11)-10(-7) M) induced concentration-dependent contractions (EC50 = 4.78 X 10(-9) M; maximal contraction = 3177+/-129 mg), whereas IRL 1620 (10(-11)-10(-7) M) produced no effect. This contraction produced by endothelin-1 was competitively blocked by BQ-123 (10(-7)-3 X 10(-6) M), and was not affected by BQ-788 (10(-6) and 10(-5) M). L-NAME (10(-4) M), meclofenamate (10(-5) M), indomethacin (10(-5) M), L-NAME (10(-4) M) plus meclofenamate (10(-5) M) and phosphoramidon (10(-4) M) did not affect the contraction in response to endothelin-1. Endothelium removal increased the response to endothelin-1, as well as the BQ-123 antagonism against endothelin-1 (pA2 values, 7.62 vs. 6.88; P < 0.01). In both intact and de-endothelized arteries precontracted with prostaglandin F2alpha endothelin-1 induced a further contraction, and IRL 1620 caused no effect. These results suggest that: (1) endothelin-1 produces cerebral vasoconstriction by activating endothelin ET(A) receptors probably located in smooth muscle; (2) endothelin ET(B) receptors, nitric oxide and prostanoids might be not involved in the cerebrovascular action of endothelin-1, and (3) endothelium removal may increase cerebrovascular reactivity by increasing sensitivity of endothelin ET(A) receptors to endothelin-1.

Coronary vasoconstriction produced by vasopressin in anesthetized goats. Role of vasopressin V1 and V2 receptors and nitric oxide

To examine the role of vasopressin V1 and V2 receptors, nitric oxide and prostanoids in the coronary vascular effects of [Arg8]vasopressin, coronary blood flow was measured with an electromagnetic flow transducer placed around the left circumflex (23 goats) or anterior descending (11 goats) coronary artery and vasopressin (0.03-1 microg) was intracoronarily injected in 34 anesthetized, open-chest goats. Basal mean values for coronary blood flow, mean systemic arterial pressure and heart rate, were 34 +/- 2.38 ml/min, 89 +/- 3.34 mmHg and 80 +/- 3.06 beats/min, respectively. Vasopressin produced dose-dependent decreases in coronary blood flow and the maximal reduction of this flow, attained with 1 microg of vasopressin, was 14 +/- 1.49 ml/min (42 +/- 2.64% of basal flow) (P < 0.01). Desmopressin (0.03-1 microg; 8 goats) did not affect significantly coronary blood flow. The intracoronary infusion of the antagonist for vasopressin V1 receptors d(CH2)5Tyr (Me) arginine vasopressin (2 microg/min per kg, 6 animals) significantly diminished the effects of vasopressin on coronary blood flow (the effects of 1 microg of vasopressin were reduced by 28%, P < 0.05). The mixed antagonist for vasopressin V1 and V2 receptors desGly-d(CH2)5-D-Tyr(Et)Val arginine vasopressin (0.2, 0.7 and 2 microg/min per kg, 9 animals) decreased in a dose-dependent manner the effects of vasopressin on coronary blood flow (the effects of 1 microg of vasopressin were decreased by 61% with 2 microg/min per kg, P < 0.01). Intracoronary infusion of saline (vehicle, 3 goats) did not change the effects of vasopressin on coronary blood flow. Intravenous administration of the inhibitor of nitric oxide synthesis N-omega-nitro-L-arginine methyl ester (L-NAME, 47 mg/kg, 9 animals) decreased resting coronary blood flow by 10% (P < 0.01) and augmented mean systemic arterial pressure by 20% (P < 0.01), without changing heart rate. During this treatment the reduction in coronary blood flow produced by vasopressin was higher than under control (the effects of 1 microg of vasopressin were increased by 28%, P < 0.01). Intravenous administration of the inhibitor of cyclooxygenase, meclofenamate (5 mg/kg, 7 animals), neither modified resting coronary blood flow, arterial pressure and heart rate nor the effects of vasopressin on this flow. These data indicate that vasopressin produces marked coronary vasoconstriction and suggest that: (a) it may be mediated by vasopressin V1 receptors, without involvement of vasopressin V2 receptors, (b) it is probably inhibited by nitric oxide under normal conditions and (c) it may be not modulated by prostanoids.

Detection of dimers of dimers of human leukocyte antigen (HLA)-DR on the surface of living cells by single-particle fluorescence imaging

The technique of single-particle fluorescence imaging was used to investigate the oligomeric state of MHC class II molecules on the surface of living cells. Cells transfected with human leukocyte antigen (HLA)-DR A and B genes were labeled at saturation with a univalent probe consisting of Fab coupled to R-phycoerythrin. Analysis of the intensities of fluorescent spots on the cell surface revealed the presence of single and double particles consistent with the simultaneous presence of HLA-DR heterodimers and dimers of dimers. The proportion of double particles was lower at 37 degrees C than at 22 degrees C, suggesting that the heterodimers and dimers of dimers exist in a temperature-dependent equilibrium. These results are discussed in the context of a possible role for HLA-DR dimers of dimers in T cell receptor-MHC interactions. The technique is validated by demonstrating that fluorescence imaging can distinguish between dimers and tetramers of human erythrocyte spectrin deposited from solution onto a solid substrate. The methodology will have broad applicability to investigation of the oligomeric state of immunological and other membrane-bound receptors in living cells.

In vitro relaxation of dog cerebral veins in response to histamine is mediated by histamine H2 receptors

There is little information on the histamine receptor mechanisms involved in cerebral venodilation, thus the role of histamine present in human cerebrospinal fluid is difficult to assess. In isolated canine pial veins, concentration-response curves to histamine (10[-7]-10[-3] M), the histamine H1 receptor agonist, 2-pyridylethylamine (10[-6]-10[-2] M), the histamine H2 receptor agonist, dimaprit (S-(3-dimethylaminopropyl) isothiourea dihydrochloride, 10[-6]-10[-2] M), and the histamine H3 receptor agonist, imetit (S-[2-(1 midazol-4-yl)ethyl]isothiourea dihydrobromide, 10[-7]-10[-3] M) were isometrically determined. In resting veins, histamine, 2-pyridylethylamine and dimaprit had no significant effect, whereas in endothelin-1-precontracted veins, these drugs produced concentration-dependent relaxation (Emax in % of active tone and pD2 were: for histamine, 72 +/- 6 and 5.36 +/- 0.09; for 2-pyridylethylamine, 59 +/- 5 and 3.28 +/- 0.05; for dimaprit, 65 +/- 7 and 4.81 +/- 0.10, respectively). The relaxations in response to histamine and dimaprit were competitively antagonized by the histamine H2 receptor antagonist, cimetidine (3 x 10[-6]-10[-4] M) (pA2 = 6.07 +/- 0.03 for histamine, and 6.09 +/- 0.07 for dimaprit), but were not affected by the histamine H1 receptor antagonist, chlorpheniramine (10[-6] M) or the histamine H3 receptor antagonist, thioperamide (N-cyclohexyl-4-(1-H-imidazol-4-yl)-1-piperidine-carbothioamide maleate, 10[-6] M). The relaxation in response to 2-pyridylethylamine was inhibited by cimetidine (10[-5] M), but not by chlorpheniramine (10[-6] M). Imetit produced a small contraction in resting veins (14 +/- 4 mg) and precontracted veins (20 +/- 3 mg), which was not modified by thioperamide (10[-6] M). The relaxation of veins in response to histamine was not modified by endothelium removal, nor by the inhibitor of nitric oxide synthase, N(G)-nitro-L-arginine methyl ester (10[-4] M), or the cyclooxygenase inhibitor, meclofenamate (10[-5] M). Therefore, in pial veins: (1) histamine produces relaxation by activation of histamine H2 receptors, probably located in the smooth musculature, with no participation of histamine H1 and H3 receptors, and (2) endothelium, nitric oxide and prostanoids are probably not involved in the relaxation in response to histamine.

Role of the purinergic and noradrenergic components in the potentiation by endothelin-1 of the sympathetic contraction of the rabbit central ear artery during cooling

1. To examine the role of the purinergic and noradrenergic components in the potentiation of endothelin-1 on the vascular response to sympathetic nerve stimulation, we recorded the isometric response of isolated segments, 2 mm long, from the rabbit central ear artery to electrical field stimulation (1-8 Hz) under different conditions, at 37 degrees C during cooling (30 degrees C). 2. Electrical field stimulation produced frequency-dependent contraction, which was reduced during cooling (about 60% for 8 Hz). Both at 37 degrees C and 30 degrees C, phentolamine (1 microM) or blockade of alpha(1)-adrenoceptors with prazosin (1 microM) reduced, whereas blockade of alpha(2)-adrenoceptors with yohimbine (1 microM) increased, the contraction to electrical field stimulation. This contraction was increased after desensitization of P2-receptors with alpha, beta-methylene adenosine 5'-triphosphate (alpha, beta-meATP, 3 microM) at 37 degrees C but not at 30 degrees C, and was not modified by blockade of P2-receptors with pyridoxalphosphate-6-azophenyl-2,4'-disulphonic acid (PPADS, 30 microM) at either temperature. 3. Endothelin-1 (1, 3 and 10 nM) at 37 degrees C did not affect, but at 30 degrees C it potentiated in a concentration-dependent manner the contraction to electrical field stimulation (from 28 +/- 6 to 134 +/- 22%, for 8 Hz). At 37 degrees C, endothelin-1 in the presence of phentolamine or prazosin, but not in that of yohimbine, alpha, beta-meATP or PPADS, potentiated the contraction to electrical stimulation. At 30 degrees C, phentolamine or yohimbine reduced, prazosin did not modify and alpha, beta-meATP slightly increased the potentiation by endothelin-1 of the response to electrical stimulation. 4. The arterial contraction to ATP (2 mM) and the alpha(2)-adrenoceptor agonist BHT-920 (10 microM), but not that to (-)-noradrenaline (1 microM), was potentiated by endothelin-1 at both 37 degrees C and 30 degrees C. 5. These results in the rabbit central ear artery suggest that the sympathetic response: (a) at 37 degrees C, could be mediated mainly by activation of alpha(1)-adrenoceptors, with low participation of P2-receptors, (b) is diminished during cooling, probably by a reduction in the participation of alpha(1)-adrenoceptors, and in this condition the response could be mediated in part by P2-receptors, and (c) is potentiated by endothelin-1 during cooling, probably by increasing the response of both postjunctional alpha(2)-adrenoceptors and P2-receptors.

Role of endothelin receptors, calcium and nitric oxide in the potentiation by endothelin-1 of the sympathetic contraction of rabbit ear artery during cooling

1. To examine further the potentiation by endothelin-1 on the vascular response to sympathetic stimulation, we studied the isometric response of isolated segments, 2 mm long, from the rabbit central ear artery to electrical field stimulation (1-8 Hz), under different conditions, at 37 degrees C and during cooling (30 degrees C). 2. Electrical stimulation produced frequency-dependent contraction, which was reduced (about 63% for 8 Hz) during cooling. At 30 degrees C, but not at 37 degrees C, endothelin-1 (1, 3 and 10 nM) potentiated the contraction to electrical stimulation in a dose-dependent way (from 43 +/- 7% to 190 +/- 25% for 8 Hz). 3. This potentiation by endothelin-1 was reduced by the antagonist for endothelin ETA receptors BQ-123 (10 microM) but not by the antagonist for endothelin ETB receptors BQ-788 (10 microM). The agonist for endothelin ETB receptors IRL-1620 (0.1 microM) did not modify the contraction to electrical stimulation. 4. The blocker of L-type Ca2+ channels verapamil (10 microM l-1) reduced (about 72% for 8 Hz) and the unspecific blocker of Ca(2+)-channels NiCl2 (1 mM) practically abolished (about 98%), the potentiating effects of endothelin-1 found at 30 degrees C. 5. Inhibition of nitric oxide synthesis with NG-nitro-L-arginine (L-NOARG, 0.1 mM) increased the contraction to electrical stimulation at 30 degrees C more than at 37 degrees C (for 8 Hz, this increment was 297 +/- 118% at 30 degrees C, and 66 +/- 15% at 37 degrees C). Endothelium removal increased the contraction to electrical stimulation at 30 degrees C (about 91% for 8 Hz) but not at 37 degrees C. Both L-NOARG and endothelium removal abolished the potentiating effects of endothelin-1 on the response to electrical stimulation found at 30 degrees C. 6. These results in the rabbit ear artery suggest that during cooling, endothelin-1 potentiates the contraction to sympathetic stimulation, which could be mediated at least in part by increasing Ca2+ entry after activation of endothelin ETA receptors. This potentiating effect of endothelin-1 may require the presence of an inhibitory tone due to endothelial nitric oxide.

Role of nitric oxide in the effects of hypoglycemia on the cerebral circulation in awake goats

This study was performed to examine the role of nitric oxide in the effects of hypoglycemia on the cerebral circulation. Hypoglycemia was induced with insulin and its effects on cerebral blood flow (measured with an electromagnetic flow transducer placed on the internal maxillary artery) were studied in awake goats under control conditions and after administration of the nitric oxide synthesis inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 47 mg/kg). Also, cerebrovascular reactivity to vasodilator stimuli was examined during insulin-induced severe hypoglycemia, before and after L-NAME treatment. In five animals under control conditions (glycemia = 90 +/- 7 mg/dl, cerebral blood flow = 64 +/- 4 ml/min, mean systemic arterial pressure = 102 +/- 4 mmHg, cerebrovascular resistance = 1.62 +/- 0.11 mmHg/ml per min and heart rate = 73 +/- 6 beats/min), insulin decreased glycemia: when hypoglycemia was moderate (glycemia = 46 +/- 2 mg/dl) or severe (glycemia = 26 +/- 1 mg/dl) cerebral blood flow increased by 25 +/- 4% and 47 +/- 6%, and cerebrovascular resistance decreased by 18 +/- 3% and 34 +/- 4%, respectively. Under basal conditions, L-NAME did not affect glycemia but reduced resting cerebral blood flow by 37 +/- 2%, increased mean arterial pressure by 33 +/- 2% and decreased heart rate by 28 +/- 3%; after L-NAME, both moderate and severe hypoglycemia did not alter significantly resting cerebral blood flow and cerebrovascular resistance. In five other goats, L-NAME, administered during severe hypoglycemia, abolished the increase in cerebral blood flow, and increased cerebrovascular resistance and mean arterial pressure over the control (normoglycemic) values. In these animals with severe hypoglycemia, acetylcholine (0.01-1 microg), isoproterenol (0.03-3 microg) and diazoxide (0.3-9 mg), injected into the internal maxillary artery, decreased cerebrovascular resistance in a dose-dependent manner, and this decrease was similar before and after L-NAME. Therefore, insulin-induced hypoglycemia may produce cerebral vasodilatation by releasing nitric oxide and may diminish the capacity of the cerebral vasculature to release nitric oxide in response to acetylcholine.

Characterization of epithelial primary cultures from human conjunctiva

Primary cultures of human epithelial cells from normal conjunctiva were developed and characterized to determine whether they retained epithelial characteristics. Conjunctival explants were obtained from the upper fornix of healthy donors and cultured in supplemented DMEM/F-12 medium for 5 days. The epithelial outgrowth was maintained for an additional 10 days. Primary cultures were then processed for light microscopy, transmission and scanning electron microscopy (TEM, SEM), and immunocytochemistry. They exhibited typical features of conjunctival epithelium on light microscopy (polygonal morphology, intimate cohesion, production of mucins), TEM (abundant desmosomes, keratin bundles, granules, microvilli), SEM (polygonal shape, microvilli, intimate cohesion), and immunocytochemistry (positivity for the receptor of epidermal growth factor, desmosomal proteins, and cytokeratins). In conclusion, primary cultures developed from normal human conjunctiva maintained the epithelial characteristics in vitro. Because the conjunctiva is a major component of the anterior ocular surface, we propose this in vitro system as suitable for physiopathologic and toxicologic studies.

Morphologic and immunocytochemical characterization of four human uveal cell lines (melanoma- and melanocytes-derived)

PURPOSE

To characterize three cell lines from human uveal melanomas and one ocular melanocyte cell line to study the specificity of several antigens in the malignant transformation of melanocytic uveal cells.

METHODS

Light microscopy (LM), transmission electron microscopy (TEM), and immunocytochemical techniques were used in the characterization of OCM-1, SP 6.5, and MKT-BR human uveal melanoma cell lines and UW-1 normal melanocyte cell line from human uvea. Several monoclonal antibodies (MoAbs) S-100, HMB-45, MNF-116, PAL-M1, NK1/C-3, IND-1, and MAAMA were used.

RESULTS

All cell lines showed an epithelioid/spindle morphology with occasional multinucleated cells, and nuclear pleomorphism. TEM showed intracytoplasmatic premelanosomes. Incubation with HMB-45 MoAb was positive in all cell lines. PAL-M2, NK1/C-3, MAAMA, and IND-1 MoAbs stainings were positive with variable intensity. MNF-116 MoAb showed negative staining in the four lines, and S-100 MoAb was also negative except for the UW-1 cell line.

CONCLUSIONS

Human uveal melanoma cell lines OCM-1, SP 6.5, and MKT-BR and the ocular melanocyte cell line UW-1 exhibited maintenance of some structural and ultrastructural characteristics of melanocytic cells. All four MoAbs, PAL-M2, NK1/C3, IND-1, and MAAMA against cutaneous melanoma-associated antigens stained positively all melanoma cell lines as well as the melanocytic cell line, suggesting that in vitro proliferation of melanocytes could modify their antigenic expression.

Peptidergic modulation of the sympathetic contraction in the rabbit ear artery: effects of temperature

1. The effects of neuropeptide Y, endothelin-1, arginine-vasopressin and angiotensin II on the vascular contraction to sympathetic nerve stimulation were studied in isolated segments, 2 mm long, from the rabbit central ear artery, a cutaneous vessel, during changes in temperature (24 degrees -41 degrees C). 2. Transmural electrical stimulation (1-8 Hz, at supramaximal voltage) produced frequency-dependent contraction, and this response, partially blocked by tetrodotoxin (1 microM) and phentolamine (1 microM), was reduced by cooling (30 degrees C -24 degrees C) and was not modified by warming (41 degrees C), as compared to that recorded at 37 degrees C. 3. Pretreatment with neuropeptide Y (10, 30 and 100 nM) increased in a concentration-dependent manner the vascular contraction to sympathetic stimulation at every temperature studied, but this potentiation was greater during cooling (34 degrees C -24 degrees C) than at 37 degrees C or warming (41 degrees C). 4. Pretreatment with endothelin-1 (3 and 10 nM) or vasopressin (0.1, 0.3 and 1 nM) increased in a concentration-dependent manner the vascular contraction to sympathetic stimulation during cooling (34 degrees C -24 degrees C), but not at 37 degrees C or warming (41 degrees C). 5. Pretreatment with angiotensin II (0.1, 0.3 and 1 microM) did not modify the contraction to sympathetic stimulation at any temperature studied. 6. These results suggest that neuropeptide Y, endothelin-1 and vasopressin, but not angiotensin II, modulate the cutaneous vasoconstriction to sympathetic nerve stimulation by potentiating this vasoconstriction during cooling.

Plasma protein binding of levamisole in several species

The binding of levamisole to total plasma proteins of 6 animal species was determined in vitro by equilibrium dialysis. The percentage of bound drug protein was independent of levamisole concentration within the range studied, 5-50 micrograms/ml (ANOVA). Levamisole was bound to a low extent to plasma proteins of each animal species (19.40-25.91%). There were significant differences in the extent of levamisole binding among species (ANOVA). Owing to the low degree of protein binding and the high volume of distribution of levamisole, the variations in protein binding due to different factors would not be of major clinical importance in its therapeutic application.

Study of the pharmacokinetic interaction between ethinylestradiol and amoxicillin in rabbits

Several antibiotics have been implicated in oral contraception failure when they are administered at the same time as the oral contraceptive (OC) pill. In the present paper, a study about amoxicillin-ethinylestradiol (EE2) pharmacokinetic potential interaction was studied. Two rabbit groups were utilized, the first group received amoxicillin (10 mg/kg) and EE2 (30, 50 and 100 micrograms/kg, respectively), both by intravenous (i.v.) route. The second group received amoxicillin (oral route, 10 mg/kg/day) and EE2 (i.v. route, 100 mu/kg) on day 1, 4 and 8 of antibiotic treatment, respectively. After compartmental (two-compartment open model) and non-compartmental analysis of plasma concentrations, the statistical study (ANOVA p < or = 0.05) revealed that the presence of amoxicillin did not modify the EE2 distribution and elimination pharmacokinetic parameters (by comparison with those obtained in a previous study where EE2 was administered alone). There also were no significant differences with the time of amoxicillin oral treatment.