Modulation of RhoA-Rho kinase-mediated Ca2+ sensitization of rabbit myometrium during pregnancy - role of Rnd3.

During pregnancy, the uterus undergoes major functional and structural remodelling. It is well known that during the major part of pregnancy, the myometrium normally remains relatively quiescent but is able to generate powerful contractions at the time of parturition. However, the intracellular molecular events regulating myometrial contractility during pregnancy still remain poorly understood. We applied differential gene expression screening using cDNA array technology to probe myometrium samples from non-pregnant and mid-pregnant (15 days) rabbits. Among the differentially expressed genes, the farnesylated small G-protein of the Rho family, Rnd3, was found to be upregulated (3.6-fold) at mid-pregnancy. Upregulation of Rnd3 was confirmed at the protein level by a 3.4-fold increase in Rnd3 expression in mid-pregnant myometrium. Measurements of contractile properties of beta-escin permeabilized smooth muscle strips revealed that the upregulation of Rnd3 correlated with an inhibition of RhoA-Rho kinase-mediated Ca2+ sensitization at mid-pregnancy. Treatment of muscle strips from mid-pregnant myometrium with the farnesyl-transferase inhibitor manumycin A (10 muM) led to the recovery of RhoA-Rho kinase-dependent Ca2+ sensitization. At late pregnancy (31 days), upregulation of RhoA and Rho kinase expression was associated with an increase in Ca2+ sensitivity of contractile proteins that was inhibited by the Rho kinase inhibitor Y-27632 (10 muM). These data thus demonstrate the time-dependent regulation of the RhoA-Rho kinase-mediated Ca2+ sensitization during the course of pregnancy. The depression of this mechanism at mid-pregnancy followed by its constitutive activation near term is associated with a co-ordinated modulation of Rnd3, RhoA and Rho kinase expression. The RhoA-Rho kinase signalling pathway and its regulators might thus represent potential targets for the development of new treatments for pre-term labour.

Induced changes of leukocyte slow rolling in an in flow pharmacological model of adhesion to endothelial cells.

BACKGROUND: Rolling of leukocytes at the surface of the vascular endothelium is a prerequisite for a subsequent firm adhesion, particularly the slow rolling appearing on ELAM CD62E. Therefore, it may be considered that increasing the rolling velocities should be a precise therapeutic target in clinical situations where leukocytes accumulate, mainly venous and arterial ischaemia. METHODS: Human neutrophils were allowed to flow on endothelial HUVECs, with and without 4 hours interleukin-1alpha activation, the cells having or not been incubated with INO5042 anti-inflammatory drug. Under a mean shear-stress of 2 dyn/cm(2), rollers and stickers were identified and quantified, using a video-camera and picture analysing software. RESULTS: When the drug had been added to endothelial cells a shift of velocities was observed towards fast speeds (from 3-5 to 7-11 microm/sec). The same results was significantly found when neutrophils, alone or along with endothelium, had been submitted to the drug, the number of stickers and rollers beeing reduced as well. Finally, such a precise pharmacological method proved efficient to detect the exact mechanism of INO5042 on white cell adhesion.

Cyclo-oxygenase and lipoxygenase pathways in mast cell dependent-neurogenic inflammation induced by electrical stimulation of the rat saphenous nerve.

1. We investigated the role of arachidonic acid metabolism and assessed the participation of mast cells and leukocytes in neurogenic inflammation in rat paw skin. We compared the effect of lipoxygenase (LOX) and cyclo-oxygenase (COX) inhibitors on oedema induced by saphenous nerve stimulation, substance P (SP), and compound 48/80. 2. Intravenous (i.v.) pre-treatment with a dual COX/LOX inhibitor (RWJ 63556), a dual LOX inhibitor/cysteinyl-leukotriene (CysLt) receptor antagonist (Rev 5901), a LOX inhibitor (AA 861), a five-lipoxygenase activating factor (FLAP) inhibitor (MK 886), or a glutathione S-transferase inhibitor (ethacrynic acid) significantly inhibited (40 to 60%) the development of neurogenic oedema, but did not affect cutaneous blood flow. Intradermal (i.d.) injection of LOX inhibitors reduced SP-induced oedema (up to 50% for RWJ 63556 and MK 886), whereas ethacrynic acid had a potentiating effect. 3. Indomethacin and rofecoxib, a highly selective COX-2 inhibitor, did not affect neurogenic and SP-induced oedema. Surprisingly, the structurally related COX-2 inhibitors, NS 398 and nimesulide, significantly reduced both neurogenic and SP-induced oedema (70% and 42% for neurogenic oedema, respectively; 49% and 46% for SP-induced oedema, respectively). 4. COX-2 mRNA was undetectable in saphenous nerves and paw skin biopsy samples, before and after saphenous nerve stimulation. 5. A mast cell stabilizer, cromolyn, and a H(1) receptor antagonist, mepyramine, significantly inhibited neurogenic (51% and 43%, respectively) and SP-induced oedema (67% and 63%, respectively). 6. The co-injection of LOX inhibitors and compound 48/80 did not alter the effects of compound 48/80. Conversely, ethacrynic acid had a significant potentiating effect. The pharmacological profile of the effect of COX inhibitors on compound 48/80-induced oedema was similar to that of neurogenic and SP-induced oedema. 7. The polysaccharide, fucoidan (an inhibitor of leukocyte rolling) did not affect neurogenic or SP-induced oedema. 8. Thus, (i) SP-induced leukotriene synthesis is involved in the development of neurogenic oedema in rat paw skin; (ii) this leukotriene-mediated plasma extravasation might be independent of mast cell activation and/or of the adhesion of leukocytes to the endothelium; (iii) COX did not appear to play a significant role in this process.

Respective role of lipoxygenase and nitric oxide-synthase pathways in plasma histamine-induced macromolecular leakage in conscious hamsters.

1. Intravital microscopy technique was used to determine the distribution of a fluorescent plasma marker (fluorescein-isothiocyanate-dextran, 150 kD; FD-150) into venular and interstitial compartments of dorsal skin fold preparations in conscious hamsters. 2. One mg kg(-1) histamine (i.v.) caused a biphasic decrease in venular fluorescence due to FD-150 extravasation in all organs (general extravasation). Immediately after injection, the venular fluorescence decreased and plateaued in 60 min. Ninety minutes after histamine injection, venular fluorescence further decreased until 180 min. Prior treatment with indomethacin (0.1 mg kg(-1), i.v.) did not modify the time-course of general extravasation but prevented histamine-induced venule dilatation. 3. Prior treatment with the 5-lipoxygenase activating protein (FLAP) inhibitor, 3-[1-(p-chlorobenzyl)-5-(isopropyl)-3-t-butylthioindol-2-yl]-2,2-d imethyl-propanoic acid sodium (MK-886)(10 microg kg(-1), i.v.), the leukotriene receptor antagonist, benzenemethanol a-pentyl-3-(2-quinolinylmethoxy) (REV-5901)(1 mg kg(-1), i.v.), or the glutathione-S-transferase inhibitor, ethacrynic acid (1 mg kg(-1), i.v.), delayed by 60 min the onset of general extravasation caused by 1 mg kg(-1) histamine. 4. Prior treatment with lipoxygenase pathway inhibitors and N(G)-nitro-L-arginine-methylester (L-NAME)(100 mg kg(-1), i.v.) abolished the general extravasation and venule dilatation induced by 1 mg kg(-1) histamine. 5. Injection of 1 microg kg(-1) (i.v.), of leukotriene-C4 (LTC4) or -D4 (LTD4) induced immediate and sustained general extravasation and reduction in venule diameter, these effects being blocked by REV-5901. 6. Histamine (1 mg kg(-1), i.v.) induced biphasic decline in mean arterial blood pressure (MAP). An initial phase (from 0 to 60 min) was followed by a late phase beginning 90 min after histamine injection. L-NAME (100 mg kg(-1), i.v.) and aminoguanidine (1 mg kg(-1), i.v.) prevented the late phase of histamine-induced hypotension. 7. Thus, plasma histamine can trigger both an immediate cysteinyl-leukotriene (Cys-LT)-dependent and a late nitric oxide (NO)-mediated inflammatory cascade. Although the cyclo-oxygenase (COX) pathway might account for histamine-induced venule dilatation, it would not influence histamine-induced extravasation.

The cyclo-oxygenase-dependent regulation of rabbit vein contraction: evidence for a prostaglandin E2-mediated relaxation.

1. Arachidonic acid (0.01-1 microM) induced relaxation of precontracted rings of rabbit saphenous vein, which was counteracted by contraction at concentrations higher than 1 microM. Concentrations higher than 1 microM were required to induce dose-dependent contraction of vena cava and thoracic aorta from the same animals. 2. Pretreatment with a TP receptor antagonist (GR32191B or SQ29548, 3 microM) potentiated the relaxant effect in the saphenous vein, revealed a vasorelaxant component in the vena cava response and did not affect the response of the aorta. 3. Removal of the endothelium from the venous rings, caused a 10 fold rightward shift in the concentration-relaxation curves to arachidonic acid. Whether or not the endothelium was present, the arachidonic acid-induced relaxations were prevented by indomethacin (10 microM) pretreatment. 4. In the saphenous vein, PGE2 was respectively a 50 and 100 fold more potent relaxant prostaglandin than PGI2 and PGD2. Pretreatment with the EP4 receptor antagonist, AH23848B, shifted the concentration-relaxation curves of this tissue to arachidonic acid in a dose-dependent manner. 5. In the presence of 1 microM arachidonic acid, venous rings produced 8-10 fold more PGE2 than did aorta whereas 6keto-PGF1alpha and TXB2 productions remained comparable. 6. Intact rings of saphenous vein relaxed in response to A23187. Pretreatment with L-NAME (100 microM) or indomethacin (10 microM) reduced this response by 50% whereas concomitant pretreatment totally suppressed it. After endothelium removal, the remaining relaxing response to A23187 was prevented by indomethacin but not affected by L-NAME. 7. We conclude that stimulation of the cyclo-oxygenase pathway by arachidonic acid induced endothelium-dependent, PGE2/EP4 mediated relaxation of the rabbit saphenous vein. This process might participate in the A23187-induced relaxation of the saphenous vein and account for a relaxing component in the response of the vena cava to arachidonic acid. It was not observed in thoracic aorta because of the lack of a vasodilatory receptor and/or the poorer ability of this tissue than veins to produce PGE2.

Smooth muscle differentiation in human vein wall at valvular level: comparison with nonvalvular wall and correlation with venous function.

The aim of this study was to evaluate local differences in smooth muscle differentiation in venous valves of patients suffering from chronic venous insufficiency, in relation to functional hemodynamic parameters measured by echo Doppler. These functional parameters did not correlate with smooth muscle differentiation at the valvular site. These results failed to support an initiating role of valvular structure in the development of chronic venous insufficiency. However, this work stresses differences in cellular differentiation of valve wall and nonvalvular smooth muscle cells in culture, and we found histologic differences in the structure of endovein and media (connective tissue relative content) between valvular and nonvalvular venous wall. The presence of smooth muscle cells in the valve cusp was demonstrated by smooth muscle alpha-actin-specific labeling and was observed to be restricted to one side of the valve cusp.

[Effect of upright tilt on venous hemodynamics in rat after three-week tail suspension]. / Effet d'une mise en orthostatisme sur l'hemodynamique veineuse chez le rat apres trois semaines de suspension.

The aim of this work was to know if the venous tone measured in vivo in rat was decreased after 3-week tail suspension, a ground-based model to simulate the effects of microgravity. Arterial and venous pressure measurements during upright tilt did not show any cardiovascular deconditioning. A longer period of tail suspension appears to be necessary to induce changes in venous tone.

Vascular remodeling in varicose veins.

The present study describes the histopathologic aspects of varicose (n=29; mean age, 52 +/- 12 years) and normal saphenous veins (n=17; mean age, 51 +/- 12 years) of patients from a similar age group. We focused on the changes that occur in the circular layer of the venous wall. We examined the venous walls by light microscopy and transmission electronmicroscopy. A semiquantitative grading system was used to assess the smooth muscle cell (SMC) hypertrophy and the change that occurs in the elastin pattern. The volume densities (Vv) of SMC and collagen were measured as well as the diameter of the SMC, and the nuclei of SMC per fixed area were counted. The varicose vein wall differed from the normal saphenous vein by the presence of hypertrophic SMC as well as disorganized elastin patterns. A correlation between the hypertrophic SMC and an abnormal elastin pattern was observed (r=0.658, p<0.001). Ultrastructurally, the SMC show prominent microherniations and vesicles that bud from the cell. These vesicles contain microfilaments and microtubuli, although no other organelles could be detected. The elastin fibers are disrupted from the hypertrophic SMC. No significant difference could be detected in both the Vv of SMC and the Vv of collagen. The diameter of the SMC in the varicose vein (d=9.45 +/- 1.22 microm) differs significantly from that in the normal saphenous vein (d=6.22 +/- 1.47 microm) (p<0.001). Also, the nuclei of SMC per fixed area differs significantly between the varicose (87 +/- 18) and nonvaricose (117 +/- 24) veins (p<0.001). We conclude that the cellular hypertrophy of the SMC and the microherniations could be the basis for disruption of the elastin fibers connected to the SMC in varicose veins. Disrupted connections between SMC and elastin fibers could in turn induce the weakness of the venous wall observed in varicose vein disease.

L-arginine and NG-nitro-L-arginine methyl ester cause macromolecule extravasation in the microcirculation of awake hamsters.

We investigated the effects of L-arginine and NG-nitro-L-arginine methyl ester (L-NAME) on macromolecule extravasation in the microcirculation of awake hamsters by computer-assisted image analysis of the distribution of FITC (fluorescein isothiocyanate)-dextran fluorescence in dorsal fold skin preparations. This analysis made it possible to simultaneously study the time course of local (skin) and general (all irrigated organs) extravasation in 180-min experiments. Bolus injection of 30 or 150 mg/kg (i.v.) L-arginine induced immediate local and general macromolecule leakage and delayed venule dilation beginning 1 h later. Injection of 20 or 100 mg/kg (i.v.) L-NAME caused rapid venule constriction followed by local and general extravasation beginning 45-60 min later. These effects of L-arginine and L-NAME were not mimicked by their biologically inactive isomers, D-arginine and D-NAME. Simultaneous bolus injection of 20 mg/kg L-NAME and 150 mg/kg L-arginine caused no significant change in fluorescence distribution or venule diameter. L-arginine effects on macromolecule extravasation were mimicked by sodium nitroprusside (10 microg/kg, i.v.) and by 8-bromo-cGMP (1 mg/kg, i.v.). Sodium nitroprusside was ineffective on venule diameter. The effects of both L-arginine and sodium nitroprusside on FITC-dextran extravasation were prevented by simultaneous injection (10 microg/kg, i.v.) of the specific inhibitor of the soluble guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). This dose of ODQ mimicked the effects of L-NAME on macromolecule extravasation and venule diameter. Taken together, these results suggest that activation or inhibition of basal NO synthesis might induce macromolecule leakage in the microcirculation of awake hamsters via temporally distinct cGMP-dependent mechanisms.

Histamine-induced biphasic macromolecular leakage in the microcirculation of the conscious hamster: evidence for a delayed nitric oxide-dependent leakage.

1. Late effects (up to 3 h) of intravenously-injected histamine on FITC-dextran extravasation were investigated in the conscious hamster, by use of computer-assisted image analysis of fluorescence distribution in a microscopic window of dorsal skin fold preparations. This analysis allowed measurement of local (skin) and general (all organs) extravasations caused by a bolus injection of histamine (1 mg kg(-1), i.v.) 2. Histamine doses higher than 0.01 mg kg(-1) caused biphasic local and general extravasations. Initial phases developed fully within 15 min (for local) and 60 min (for general) and were followed by late phases beginning 90 min after histamine injection. Although the initial and late phases of histamine-induced extravasations had differential apparent reactivities to the autacoid, all the effects of histamine on the microcirculation (1 mg kg[-1]) were inhibited by pyrilamine (1 mg kg(-1), i.v.) but not by cimetidine (1 mg kg(-1), i.v.). 3. Pretreatment with N(G)-monomethyl-L-arginine (L-NMMA, 30 mg kg(-1), i.v.) or N(G)-nitro-L-arginine methyl ester (L-NAME, 100 mg kg(-1), i.v.) did not affect the initial phases but did prevent the late phases of local and general extravasations triggered by 1 mg kg(-1) histamine. The inhibitory effects of L-NAME were reversed by L-arginine (30 mg kg[-1]) but not by D-arginine (30 mg kg[-1]) according to the enantioselectivity of nitric oxide synthase (NOS). A late NO-mediated venular dilatation occurred in response to plasma histamine. 4. A low dose of aminoguanidine (1 mg kg(-1), i.v.), a selective inhibitor of the inducible isoform of NOS (iNOS), mimicked the inhibitory effects of L-NAME on the late phases of histamine-induced macromolecular extravasations and venular dilatation. 5. Pretreatment with dexamethasone (1 mg kg(-1), i.v.) prevented both the initial and late phases of histamine-induced extravasations. Fucoidan (1 or 25 mg kg(-1), i.v.) prevented the late phases without affecting initial phases, consistent with a role for leukocytes adhesion in the development of the late NO-mediated effects of histamine. 6. We conclude that intravenous injection of histamine triggers a biphasic inflammatory cascade via initial activation of H1 receptors which induces a late NO-mediated PMN-dependent extravasation process.

Venous tone and repeated +Gz accelerations.

The purpose of the present work was to study in vivo in rat the consequences of repeated exposures to sustained +Gz centrifugations on the venous pressure and on the venous tone, that one evaluated by measuring the equilibrium pressure of all vessels in the circulation when the flow is null or MCFP (mean circulatory filling pressure).

The venous tone is not altered after three-week tail suspension in rats.

Cardiovascular deconditioning observed in humans during spaceflight has been suggested to be related in part to changes in venous compliance, mechanisms including skeletal muscle deconditioning. However, increased venous compliance was observed during very short term simulations (24 to 48 hours), and during an over 28-day simulation the hyperdistensibility tended to decrease whereas the muscular changes were still present (2). In the first case, muscular changes can not explain the venous alterations because of the short delay. In the second case, the relationship between muscular and venous alterations disappeared. Finally, it is suggested that factors other than muscular ones could explain the changes in venous compliance observed during spaceflights. The fact that orthostatic hypotension has never been observed after hindlimb suspension in the rat raises issue with the use of tail-suspended rats as a valid model for the study of the mechanisms involved in cardiovascular deconditioning induced by spaceflight in humans. However, in vitro altered responsiveness of the vena cava to norepinephrine were observed in rat after spaceflight and tail suspension. The purpose of the experiments was to verify if any change occurs in venous tone measured in vivo in rats after three-week tail suspension.

Roles of NO-synthase and cyclooxygenase in sex- and pregnancy-dependent arterial and venous pressures in the rat.

The roles of NO synthase (NOS) and cyclooxygenase on vascular pressures were studied as a function of sex and pregnancy. After anesthesia, mean arterial pressure (MAP) and mean circulatory filling pressure were lower in pregnant rats compared with male and virgin rats, but N(G)-nitro-L-arginine methyl ester (L-NAME; 30 mg/kg) induced similar increases in MAP. Pithing abolished these pressure differences, suggesting a diminished autonomic reflex in pregnancy, and led in pregnant rats to a lower arterial and venous NO modulation. In separately perfused mesenteries, the lower responses to KCI observed in venous beds of female compared with male rats do not involve any dysfunction of NOS activity in the mesenteries isolated from virgin and pregnant rats. The cyclooxygenase pathway is implicated in the KCl-induced responses of vessels taken from male rats and of venous mesentery from pregnant rats. But prostanoids do not share in the acetylcholine (ACh)-induced relaxations in the arterial and venous K+-contracted mesenteric vasculatures isolated from any of the groups of rats.

Comparison of the nitric oxide and cyclo-oxygenase pathway in mesenteric resistance vessels of normotensive and spontaneously hypertensive rats.

1. The double perfused mesentery was used to compare arterial and venous KCl- and acetylcholine (ACh)-induced responses in tissues taken from normotensive (WKY) and spontaneously hypertensive rats (SHR) in the presence or absence of inhibitors of nitric oxide (NO) synthase (NG-nitro-L-arginine (L-NOARG) and NG-nitro-L-arginine methyl ester (L-NAME)) and cyclo-oxygenase (indomethacin, mefenamic acid). 2. KCl (20 to 120 mM K+) caused concentration-dependent increases in arterial and venous perfusion pressures. The maximal arterial effects were significantly higher in the SHRs than in the WKY, with no differences in the venous pressor responses. 3. L-NAME and L-NOARG (100 microM) had no effect on the basal perfusion pressures in tissues from either WKY or SHRs, and mefenamic acid only induced a significant reduction of the basal perfusion pressures in the venous mesenteric vessels isolated from WKY. 4. L-NAME and L-NOARG (100 microM) potentiated the pressor responses to KCl to the same extent in the venous and arterial beds derived from WKY and SHR, while indomethacin and mefenamic acid (5 microM) only significantly decreased these responses in WKY. 5. Acetylcholine (ACh)-induced relaxations (1 nM to 10 microM) were significantly higher in arterial beds of WKY than in SHR, without differences in the venous relaxant responses. 6. L-NAME (100 microM) inhibited ACh-induced relaxations in arterial and venous beds from both groups of rats. Mefenamic acid was without effect on ACh-induced relaxations in either the arterial or the venous beds from WKY and SHR. 7. In conclusion, the liberation of NO in the perfused mesenteric vasculatures requires an active tone and no dysfunction of NO synthase activity is functionally apparent in the mesenteries isolated from SHRs. The cyclo-oxygenase pathway is only implicated in the KCl-induced responses of tissues derived from WKY, but not in the vasodilatations induced by ACh in either the arterial or the venous vasculatures from WKY and SHR.

Progesterone receptor expression in human saphenous veins.

BACKGROUND: Clinical and epidemiological observations regarding varicose veins, such as their predominance in women and the occurrence of venous stasis during sex-hormone therapy, the luteal phase of the menstrual cycle, and pregnancy, suggest a sex hormone-dependency of this venous pathology. In the present study, analysis of steroid receptors was used to determine if these effects were due to a direct hormonal action on the saphenous vein. METHODS AND RESULTS: Biopsy samples were obtained from patients undergoing stripping removal of varicose saphenous veins. Patients were men (n = 5) and premenopausal (n = 15) or postmenopausal (n = 10) women. Progesterone receptors (PR) and estrogen receptors (ER) were determined by both enzyme immunoassay (EIA) and immunocytochemistry by use of monoclonal antibodies. Ninety percent of the biopsy samples showed PR positivity by EIA (range, 5 to 53 fmol/mg cytosol protein). When present, PR staining was observed in the cell nuclei of the tunica media and the subendothelial layer (neointima). No significant variation was observed in the PR content of different regions within the same saphenous vein. In contrast, no ER or extremely low levels of ER (< 5 fmol/mg cytosol protein) were detected by EIA in 25 of 30 varicose biopsy samples. Reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze PR and ER mRNAs in biopsy samples that were PR positive/ER negative. With primers to the hormone-binding region encoded by PR mRNA, a RT-PCR product of the expected size was detected and its identity confirmed by Southern blot by use of a PR cDNA probe. In contrast, no RT-PCR product could be detected by use of primers to the DNA-binding domain, the hinge region, and the ligand-binding domain encoded by ER mRNA. CONCLUSIONS: These results indicate that human saphenous veins from both sexes express PR, as previously described for arterial blood vessels. This observation suggests that progesterone acts directly on these veins via a classic receptor-mediated pathway.

[Venous hemodynamics of the lower limbs]. / Hémodynamique veineuse des membres inférieurs.

Low pressure venous return results from several different pump systems. Blood flow and velocity depend on sympathetic tone and contraction of the veins modulating distensibility. In patients with chronic venous insufficiency, different components including hyperdistensibility, hyperpressure, valve failure, back-flow and stasis, lead to a vicious circle. These elements modify the venous wall and lead to hyperdistension producing modified distensibility and/or formation of varicose veins. Endothelial and smooth muscle cells participate in these changes. Smooth muscle cells play a major role: some hypertrophy and/or lose their contractility, synthesizing and sometimes rapidly destroying tissue. These changes in the circulation, sometimes increased by inflammation and thrombosis, affect microcirculatory haemodynamics with a variable delay. The venous system, even when pathological (as long as it is not totally invaded by fibrosis) responds to a large number of relaxing or constricting pharmacological agents, justifying their therapeutic value.

[Artemisia monosperma of the coastal plain as an allergen source in Jerusalem].

The possibility that pollen grains of Artemisia monosperma (AM) are transported to Jerusalem from their native habitat along the coastal plain was investigated. Air-borne pollen grains were sampled in the early autumn of 1989 with a Rotorod pollen sampler. During that period only 1 of the 4 species of AM in Israel, A. monosperma, was flowering. The sampling day was typical for the late summer, with a light NW breeze. Sampling was done simultaneously in 3 sites: Tel Aviv, Carmei Yosef and Jerusalem. The greatest concentration of pollen in Tel Aviv was found during the morning hours and decreased during the course of the day. Pollen counts in Carmei Yosef reached a maximum at 11:00 a.m. A substantial number of air-borne AM pollen was recorded in Jerusalem, with a daily peak at 1:00 p.m. Such results fit well the distribution pattern of the pollen as expected from the recorded wind velocity and direction. They also agree well with the data for transportation of other air pollutants from the coastal plain to Jerusalem. Apparently AM pollen is transported to Jerusalem over distances of many tens of kilometers, even on days with light winds. Therefore, such pollen may constitute an allergenic factor in Jerusalem in the autumn. It is reasonable to assume that transportation of pollens of other coastal plants follows a similar pattern.

Effect of parathyroidectomy on development of hypertension and atrial responsiveness in spontaneous hypertensive rats.

1. In order to further clarify the relationships between parathyroid function and development of hypertension, the effects of parathyroidectomy (PTX) on blood pressure and on responsiveness of atria isolated from spontaneous hypertensive rats (SHR) were examined. 2. PTX was carried out in 6-week-old SHR and normotensive Wistar rats. The experiments were performed 2 weeks after surgery. 3. PTX reduced the plasma calcium concentration and decreased atrial calcium content in SHR. On the other hand, basal contractile force and beat frequency of isolated atria were higher in PTX SHR than in sham-operated SHR. In response to cumulative addition of isoprenaline, atria from PTX SHR displayed diminished inotropic and chronotropic responses compared with sham-operated SHR. Similar results were obtained in atria isolated from Wistar rats. When calcium sensitivity was studied in atria from Wistar rats, basal and isoprenaline-induced maximum contractile forces were higher in PTX group than in the sham-operated group. Nevertheless, basal and isoprenaline-induced maximum contractile forces, determined at the respective plasma ionized calcium concentration of PTX and sham-operated groups (0.83 and 1.22 mmol/L), were not significantly different. 4. Our results do not favour a role for alteration in atrial activity as a causal mechanism in delayed development of experimental genetic hypertension after parathyroidectomy.

The protective action of R56865 against ouabain-induced intoxication in rat heart isolated atria and ventricles.

The action of R56865 has been examined on the contractile effects produced by ouabain concentrations interacting with high (3 microM) and low (300 microM) affinity digitalis receptors on electrically stimulated ventricular strips isolated from rat. R56865 1 microM reduced the increase in resting tension produced by ouabain 300 microM and left unalterated the inotropic effect evoked by ouabain 3 and 300 microM that was reduced by higher concentrations (3 and 6 microM) of R56865. The action of R56865 was also studied on ouabain-induced intoxication in electrically stimulated and spontaneously beating atria of rat. On electrically stimulated (3 Hz) whole atria, R56865 0.3 microM reduced the maximal increase in resting tension produced by ouabain 300 microM and delayed the time to onset of the ouabain-induced arrhythmias but did not affect ouabain's inotropic effect. Higher concentrations of R56865 were required to reduce the inotropic effect of ouabain. The protective action of R56865 against ouabain-induced intoxication was most pronounced on spontaneously beating atria where it reduced spontaneous rate of beats. Experiments in electrically driven left atria indicated that only a part of the protective effect of R56865 could be related to its bradycardic action. The effect of R56865 was also examined on ouabain-induced inhibition of sodium pump in human red blood cells. R56865 6 microM did not modify the inhibition produced by ouabain (from 0.3 to 10 nM), this indicates that the protective action of R56865 against ouabain-induced intoxication is not due to an interaction with the inhibitory effect of ouabain on sodium pump.

Pharmacology of endothelin-1 in isolated vessels: effect of nicardipine, methylene blue, hemoglobin, and gossypol.

Sensitive bioassay tissues for porcine endothelin-1 (ET-1) were developed in a cascade superfusion system and in organ baths. Venous preparations of the rabbit and rat were more sensitive than arterial preparations. ET-1 had a different pharmacological profile than Bay K 8644 on the various preparations. Nicardipine (0.1-1 microM) abolished the responses to Bay K 8644 without affecting those induced by ET-1. Thus, ET-1 contracts venous and some arterial vessels via specific receptors or channels that differ from dihydropyridine-sensitive calcium channels. Methylene blue and hemoglobin potentiated responses to ET-1 in endothelium-denuded venous vessels, whereas gossypol had no effect.