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E H Ohlstein

Publications and source records attributed to E H Ohlstein.

At least 91 records · Page 5Linked to original sources
PubMed1995

Pharmacological evidence for the presence of three distinct functional endothelin receptor subtypes in the rabbit lateral saphenous vein.

1. Contraction of the rabbit isolated saphenous vein is mediated by a heterogeneous endothelin (ET) receptor population. This study has characterized these receptor subtypes by use of several pharmacologically distinct ET receptor agonists and antagonists. 2. ET-1, ET-3, sarafotoxin S6c (STXc) and [Ala3,11]ET-1 produced biphasic, concentration-dependent contractions of the saphenous vein, responses which were best fitted by a two-site model comprised of a high (pM) and a low (nM) affinity site. In contrast, IRL 1620 only recognized one of these sites. ET(16-21) was devoid of contractile activity. ET-1, ET-3 and STXc were equipotent at the high affinity site (pD2s of 12.0 +/- 0.2, 12.2 +/- 0.2 and 12.3 +/- 0.3) indicating that this site had the characteristics of an ETB receptor. In contrast, the low affinity site had the functional characteristics of an ETc receptor since the pD2s for ET-3 (10.2 +/- 0.3) and STXc (10.6 +/- 0.3) were significantly greater than that for ET-1 (9.1 +/- 0.1). These contractile responses were insensitive to BQ-123, confirming that ETA receptors were not involved in mediating this effect. 3. SB 209670 differentially antagonized the high affinity phases of the isopeptide concentration-response curves in a fashion dependent on the competing agonist: relative to the KB obtained against STXc (0.15 nM). SB 209670 was 10 fold less potent when ET-1 was used as the competing agonist. This differential effect was not evident at the low affinity site (KB = 38 nM). SB 209670 produced parallel, concentration-dependent rightward shifts in the concentration-response curve to STXc Ro 47-0203 was approximately 1 to 2 orders of magnitude less potent than SB 209670 at inhibiting the high affinity component of the concentration-response curve to STXc, whereas BQ-788 and Ro 46-2005 were approximately 3 orders of magnitude less potent than SB 209670. In addition to RES-701 and BQ-123, the high affinity site was insensitive to PD 142893 suggesting that it may represent an ETB2 receptor. Ro 47-0203 and SB 209670 were equipotent at inhibiting the low affinity component of the STXc concentration-response curve. Although Ro 46-2005, BQ-788, PD 142893 and RES-701 produced significant antagonism at the low affinity site, they were at least ten fold less potent than SB 209670. 4. ET-1, ET-3 and STXc produced endothelium-dependent vasorelaxation in the precontracted saphenous vein. Antagonist IC50s were approximated as being: SB 209670, 3 nM; BQ-788 and RES 701,300 nM; Ro 46-2005 and PD 142893, 3 microM; BQ-123, > 10 .M, consistent with vasorelaxation being mediated by an ETB1 receptor.5. In summary, three pharmacologically distinct ET receptor subtypes have been identified in the rabbits aphenous vein. Two contractile receptors are present on the vascular smooth muscle, a high affinity site with the characteristics of an ETB2 receptor and a distinct lower affinity site with the characteristics of an ETc receptor. In addition, an ETBI receptor is present on the endothelium which mediates the vasodilator actions of this peptide family.

Animals↗
PubMed1995

Antihypertensive actions of the novel nonpeptide endothelin receptor antagonist SB 209670.

Indirect evidence has implicated endothelin-1 in the pathogenesis of hypertension. In the present study we examined such a role directly with SB 209670, a novel nonpeptide endothelin receptor antagonist. The antihypertensive and hemodynamic effects of SB 209670 were examined in conscious, unrestrained spontaneously hypertensive (SHR), normotensive Wistar-Kyoto (WKY), and renin-hypertensive rats. Sustained intravenous infusion of SB 209670 (10 micrograms.kg-1.min-1 for 6 hours) produced a significant, reversible reduction in mean arterial pressure in SHR but not in WKY rats. The antihypertensive response to 10 micrograms.kg-1.min-1 SB 209670 (approximately 25 mm Hg reduction in blood pressure) was associated with bradycardia (16% decrease in heart rate) but only a minimal reduction (3%) in cardiac output, because stroke volume was evaluated (by 15%). Therefore, the antihypertensive effect of SB 209670 resulted from a decrease (13%) in total peripheral resistance. A sustained antihypertensive effect could also be observed after intraduodenal administration of SB 209670 (3 mg/kg) in conscious SHR (reduction of approximately 35 mm Hg 5 hours after administration). SB 209670 (3 mg/kg intravenous bolus) did not alter the pressor response or tachycardia observed in pithed SHR after stimulation of thoracolumbar sympathetic outflow. SB 209670 was also antihypertensive in renin-hypertensive rats, lowering blood pressure to an extent similar to that observed in SHR. Thus, the data presented provide evidence to support a role for endothelin-1 in the pathophysiology of two animal models of hypertension.

Animals↗
PubMed1995

Nonpeptide endothelin receptor antagonists. V: Prevention and reversal of acute renal failure in the rat by SB 209670.

The ability of the mixed endothelin (ETA/ETB) receptor antagonist (+/-)-SB 209670 to prevent and reverse ischemia-induced acute renal failure (ARF) was studied in rats with moderate and severe ARF. Uninephrectomized, chronically instrumented Sprague-Dawley rats were used. Moderate and severe ARF was induced by occlusion of the renal artery for 30 and 45 min, respectively. During the 24 hr after 30-min ischemia (moderate ARF), glomerular filtration rate (GFR) decreased by 95%, and fractional excretion of sodium increased from 0.6% to 10%. Infusion of (+/-)-SB 209670 at 10, 30 and 100 micrograms/kg.min for 30 min before, during and 60 min after renal ischemia had a moderate effect on renal function. Thus, with the highest dose, the ischemia-induced reduction in GFR was 70%. This dose, however, had no effect in rats when given before, during and after 45 min of renal ischemia (severe ARF). In contrast, when infused at 30 micrograms/kg.min for 3 hr on the day after ischemia, (+/-)-SB 209670 markedly increased survival rate (75%) in rats with severe ARF by significantly increasing tubular reabsorption of Na+, followed by a slow and gradual increase in GFR and reversal of the increase in plasma K+ concentration. Data from acute renal clearance studies in rats with moderate ARF showed that when infused 24 hr after ischemia, (+/-)-SB 209670 acutely reversed the impairment in sodium reabsorption without increasing GFR or renal blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1995

Selective ETA receptor antagonism with BQ-123 is insufficient to inhibit angioplasty induced neointima formation in the rat.

OBJECTIVE: The aim was to assess whether or not the endothelin ETA receptor selective antagonist BQ-123 could inhibit neointima formation in vivo following balloon angioplasty. METHODS: The effect of either acute administration of BQ-123 (0.1 mg.kg-1.min-1 intra-arterial infusion for 1 h before and 1 h after angioplasty) or chronic administration (bolus intraperitoneal injection, 2.5 mg.kg-1 twice daily; continuous intraperitoneal infusion, 0.8 and 8 mg.kg-1.d-1) on neointima formation was examined in rats which had undergone left common carotid artery balloon angioplasty. RESULTS: Neither acute intra-arterial infusion nor either mode of chronic intraperitoneal administration of BQ-123 had a significant effect on the degree of neointima formation observed following balloon angioplasty. CONCLUSIONS: Neither acute nor chronic ETA receptor blockade is sufficient to inhibit angioplasty induced neointima formation in the rat. Since it was previously shown that the ETA/B antagonist SB 209670 was effective in this model, while the ETA selective antagonist BQ-123 is now found to be ineffective, the data implicate the ETB receptor subtype in the pathogenesis of neointima formation.

Angioplasty, Balloon↗
PubMed1995

Use of differential display to identify differentially expressed mRNAs induced by rat carotid artery balloon angioplasty.

BACKGROUND: We have used differential display technology in an animal model of arterial restenosis to study the molecular mechanisms of neointima formation. EXPERIMENTAL DESIGN: Balloon angioplasty of the rat common carotid artery was performed, and tissues were examined from naive animals (control) and from animals that had undergone angioplasty 6 hours, 3 days, and 14 days earlier. Total RNA was isolated, and differential display was performed to identify mRNA transcripts whose expression is modulated in a temporal fashion as a consequence of balloon angioplasty. RESULTS: Using total RNA isolated from vessels excised from naive rats and those from rats that underwent angioplasty up to 14 days earlier, we describe two differentially regulated transcripts by differential display and verify the expression pattern of these same transcripts by Northern analysis. DNA sequence analysis has identified one of these angioplasty-induced transcripts as a novel sequence and the other as the tryptophan hydroxylase and protein kinase C regulatory protein 14-3-3 gamma. CONCLUSIONS: In this study, we describe the in vivo application of the differential display technique in a rat carotid artery angioplasty model to identify mRNA transcripts whose expression is modulated selectively in vessels undergoing neointima formation. Use of this technique in animal models of disease should facilitate our understanding of gene expression patterns in pathogenesis and may serve as a reliable technique to "fingerprint" disease processes.

14-3-3 Proteins↗
PubMed1995

Endothelin-1-evoked calcium transients in UMR-106 osteoblastic osteosarcoma cells are mediated through endothelin-A and endothelin-B receptors.

Endothelin (ET) receptor subtypes involved in the modulation of intracellular calcium were studied in UMR-106 osteoblastic osteosarcoma cells. Calcium signaling in UMR-106 cells in suspension was determined with fluo-3-acetoxymethylester fluorescent dye. ET-1 and the ETB-selective agonist sarafotoxin 6c (S6c) elicited rapid calcium transients. Maximally effective concentrations of the ETA-selective antagonist BQ-123 [Cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu)] attenuated ET-1-evoked calcium transients by only 50%. BQ-123 had no effect on S6c-stimulated transients. ET-1 and S6c showed homologous desensitization on repeated administration. Pretreatment with ET-1 completely eliminated S6c-evoked calcium transients, whereas S6c pretreatment only partially (50%) attenuated the calcium transient evoked by ET-1. Joint pretreatment with S6c and BQ-123 or pretreatment with the ETA/ETB nonselective antagonist PD-142893 (Ac-D-diphenylalanine-Leu-Asp-Ile-Ile-Trp) eliminated the ET-1-stimulated calcium transient. These cells display both ETA and ETB receptors (60:40), as demonstrated by saturation binding experiments with [125I] ET-1 and the ETB specific agonist, [125I] IRL-1620 (Suc [Glu9, Ala11,15] endothelin-1 [8-21]). This was further confirmed by competition binding experiments using [125I] ET-1 and subtype-selective ligands S6c and BQ-123. These data indicate that ET-1 interacts with both ETA and ETB receptors to elicit calcium transients in UMR-106 osteoblastic osteosarcoma cells.

Amino Acid Sequence↗
PubMed1995

Nonpeptide endothelin receptor antagonists: IV. Identification of receptors in rabbit colonic mucosa and smooth muscle and correlation with physiological effects.

Endothelin (ET) has been previously demonstrated to be a potent intestinal secretory stimuli and to elicit intestinal smooth muscle contractions. In rat distal colon, the ETA receptor antagonist cyclo[D-Asp-L-Pro-D-Val-L-Leu-D-Trp] abolishes the changes in ion transport (as measured by short-circuit current) elicited by ET-1. In this study, effects of ET-1, sarafotoxin 6c and "big" ET in the absence and presence of the endothelin receptor antagonists cyclo [D-Asp-L-Pro-D-Val-L-Leu-D-Trp] and (+/-)-3-[2-(carboxymethoxy)-4-methoxyphenyl]-1-[3,4- (methylenedioxy)phenyl]-5-(prop-1-yloxy)indan-2-carboxylic acid on ion transport in rabbit distal colon were assessed through measurement of short-circuit current changes in segments of muscle-stripped mucosa in Ussing chambers. In addition, changes in smooth muscle contraction in response to acetylcholine, ET-1, ET-3 and sarafotoxin 6c in the absence and presence of (+/-)-3-[2-(carboxymethoxy)-4-methoxyphenyl]-1-[3,4- (methylenedioxy)phenyl]-5-(prop-1-yloxy)indan-2-carboxylic acid and of cyclo [D-Asp-L-Pro-D-Val-L-Leu-D-Trp] were measured in mucosa-free preparations oriented along their longitudinal axes. Receptor binding studies with mucosal or smooth muscle homogenates were conducted with [125I]ET-1, with [125I]ET-3 and with [125I]Tyr13Suc-[Glu9,Ala11,15]-endothelin-1(8-21 ) to identify the subtypes of ET receptors present in these preparations. From studies with rabbit colonic mucosa, both binding studies and measurement of short-circuit current confirm that the ETB receptor subtype is the predominant subtype and is responsible for the changes observed in ion transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Pharmacologic evidence for the presence of three functional endothelin receptor subtypes in rabbit saphenous vein.

The contractile responses to endothelin-1 (ET-1), endothelin-3 (ET-3), and sarafotoxin S6c (STXc) were best-fitted by a two-site model in the rabbit isolated saphenous vein. Agonists were equipotent at the high-affinity site (pD2s 12.0 +/- 0.2, 12.2 +/- 0.2, and 12.3 +/- 0.3, respectively), characteristic of an ETB receptor, whereas ET-3 and STXc were significantly more potent than ET-1 as vasoconstrictors at the low-affinity site (pD2s 10.2 +/- 0.3, 10.6 +/- 0.3, and 9.1 +/- 0.1, respectively), characteristic of an ETC-like receptor. The high affinity, ETB-mediated response was inhibited by SB 209670, Ro 47-0203, BQ-788, and Ro 46-2005 (Kbs of 0.15, 14, 110, and 280 nM against STXc, respectively) but was insensitive to PD 142893, RES-701 and BQ-123 (Kbs > or = 10 microM), consistent with this response being mediated by the ETB2-like receptor subtype. The low-affinity ETC-like-mediated component was inhibited by SB 209670, Ro 47-0203, BQ-788, Ro 46-2005, PD 142893, and RES-701 (Kbs 38 nM, 62 nM, 670 nM, 580 nM, 1.7 microM, and 2.0 microM, respectively), but was insensitive to BQ-123 (Kb > or = 10 microM). ET-3 produced endothelium-dependent vasorelaxation in the presence of active tone. Antagonist IC50s were approximated as being: SB 209670 3 nM; BQ-788 and RES 701,300 nM; Ro 46-2005 and PD 142893 3 microM; BQ-123 > or = 10 microM. These values were consistent with vasorelaxation being mediated by an ETB1-like receptor. Therefore, three pharmacologically distinct ET receptor subtypes have been identified in rabbit saphenous vein. Two contractile receptors, ETB2-like and ETC-like, are present on the vascular smooth-muscle receptor, whereas an ETB1-like receptor, which mediates the vasodilator actions of this peptide family, is present on the endothelium.

Animals↗
PubMed1995

Endothelin receptor subtypes in the pathogenesis of angioplasty-induced neointima formation in the rat: a comparison of selective ETA receptor antagonism and dual ETA/ETB receptor antagonism using BQ-123 and SB 209670.

The present study compared the vasculoprotective efficacy of acute and chronic endothelin (ET) ETA or dual ETA/B receptor antagonism in the rat common carotid artery (RCCA) model using BQ-123 and SB 209670. Acute intra-arterial infusion (0.1 mg/kg/min) for 2 h at the time of angioplasty of either BQ-123 or SB 209670 did not attenuate the neointima lesion formation observed 2 weeks after angioplasty (neointima:media ratios of 137% and 116% of control, respectively). In contrast, chronic administration of SB 209670 (bolus i.p. injection, 2.5 mg/kg b.i.d.) attenuated lesion formation (neointima:media ratio inhibited by 52% relative to vehicle control; p < 0.05). An identical dosage regimen of BQ-123 did not exhibit significant vasculoprotection (neointima:media ratio of 128% vehicle control). However, this dosage regimen of BQ-123 was associated with significant and selective ETA receptor antagonism. The systemic pressor response to exogenous ET-1 administration was inhibited by 91% (p < 0.05), whereas the associated depressor response was not different from that observed in vehicle-treated rats. Therefore, since chronic administration of pharmacologic doses of the ETA-selective antagonist BQ-123 does not prevent lesion formation in the RCCA model, whereas the ETA/B receptor antagonist SB 209670 is vasculoprotective, the data implicate a significant role for the ETB receptor subtype, either exclusively or in concert with ETA receptor activation, in the pathogenesis of neointima formation in the rat.

Angioplasty, Balloon↗
PubMed1995

Temporal expression of ECE-1, ET-1, ET-3, ETA, and ETB receptor mRNAs after balloon angioplasty in the rat.

The temporal expressions of endothelin-converting enzyme-1 (ECE-1), preproendothelin-1 (preproET-1), preproET-3, and ETA, ETB receptor mRNAs were studied in rat carotid artery after balloon angioplasty using quantitative reverse transcription and the polymerase chain reaction (RT-PCR). The expression profile of these messages revealed that the increases of ECE-1 mRNA preceded those of preproET-1 and preproET-3. A significant increase in ECE-1 mRNA was observed at 6 h (1.8-fold, p < 0.01) and 24 h (1.7-fold, p < 0.01) after angioplasty, whereas a significant increase in preproET-1 mRNA levels was not observed until day 3 (1.9-fold, p < 0.05) and day 7 (2.1-fold, p < 0.05). A similar delayed increase in preproET-3 mRNA was observed at day 7 (2.8-fold, p < 0.05) and day 14 (2.6-fold, p < 0.05) after angioplasty. The levels of ETA receptor mRNA were elevated 29.3-fold (p < 0.001) and 24.3-fold (p < 0.01) at days 3 and 7 after angioplasty, respectively. The increase in ETB receptor mRNA occurred slightly earlier than that of ETA receptor, showing a 15.1-fold increase at day 1 (p < 0.001) and a 11.3-fold increase at day 3 (p < 0.01) after angioplasty. The data suggest that ECE-1, ET-1, ET-3, and ETA and ETB receptors play an active role in the pathogenesis of neointima formation.

Angioplasty, Balloon↗
PubMed1995

Agonist-dependent inhibition by peptide and nonpeptide endothelin receptor antagonists in the rabbit isolated pulmonary artery.

This study examined the effect of peptide and nonpeptide endothelin (ET) receptor antagonists on the contractile actions of ET-1 and sarafotoxin S6c (STXc) in the rabbit isolated pulmonary artery (RbPA). The peptide antagonists BQ-123, BQ-788, and RES-701 (10 microM) did not inhibit ET-1-induced RbPA contractions. The nonpeptide antagonists PD 156123, Ro 47-0203, and SB 217242 (10 microM) also had no effect on ET-1--induced contractions. In contrast, the nonpeptide antagonists SB 209670 and L-749,239 (10 microM) both caused a shift to the right of the ET-1 concentration-response curve (Kbs of 231 nM and 1.42 microM, respectively) and a two- to three-fold increase in nH (Hill slope), without altering the Rmax (maximal agonist-induced contraction). Contractile responses to STXc were unaffected by BQ-123, RES-701, and PD 156123 (10 microM). SB 209670, SB 217242, L-749,239, Ro 47-0203, and BQ-788 (10 microM) caused a shift to the right of the STXc response curve (Kbs of 16, 353, 202, 1,303 and 1,499 nM, respectively) and an increase in nH and Rmax. SB 209670 and L-749,239 were both approximately 10-fold more potent in antagonizing STXc than ET-1. Assuming, at best, Kbs of 10 microM for SB 217242, Ro 47-0203, and BQ-788 against ET-1, these antagonists were also at least 10-fold more potent in blocking STXc. The effects of various incubation and washout times on the antagonistic properties of SB 209670 (1 microM) against STXc were studied. Washing the antagonist from the tissue bath caused a 100-fold decrease in affinity (Kbs of 23-2,373 nM at 0 and 30 min, respectively) and a return to near control levels of nH (within 30 min). In contrast, the augmented Rmax response did not return to control levels until 6 hr later. As the incubation time was increased, the augmented Rmax was sustained (6 h), but affinity decreased (Kbs of 21 and 793 nM after 5 min and 6 h of incubation), and nH returned to near control values. In conclusion, agonist-dependent inhibition by ETB receptor antagonists is observed in the RbPA. Heterogenous populations of ET receptors, differential binding domains, and/or functionally uncoupled receptors may account for this phenomenon.

Animals↗
PubMed1995

The endothelin receptor antagonist SB 217242 reduces cerebral focal ischemic brain injury.

Previously, we demonstrated that cerebral focal ischemic tissue exhibits a significant increase in immunoreactive endothelin (ET). Because increased ET might exacerbate the consequences of cerebral ischemia, we evaluated the effects of the orally active ETA/B receptor antagonist SB 217242 on middle cerebral artery occlusion (MCAO) in the spontaneously hypertensive rat (SHR). SHRs were treated b.i.d. with vehicle or with 3 or 15 mg/kg SB 217242 p.o. for 7 days. Permanent MCAO was performed on day 7 and animals were sacrificed on day 8. Forebrains were stained and the extent of cerebral (i.e., cortical) infarction was determined using image analysis. Hemispheric swelling (%), hemispheric infarct (%), and infarct volume (mm3) were quantitated for each animal. SB 217242 treatment produced a significant decrease in ischemic brain injury. Hemispheric infarction and infarct volume were reduced after the 15 mg/kg treatment (12.0 +/- 1.1% and 69 +/- 6 mm3) compared to vehicle (17.3 +/- 1.5% and 99 +/- 8 mm3) (p < 0.05). No significant effects on hemispheric swelling were observed. This is the first demonstration of an ET receptor antagonist exhibiting efficacy in cerebral focal ischemia. The fact that a 30% reduction in ischemic brain injury can be demonstrated after oral administration of SB 217242 suggests that ET antagonists may be of therapeutic utility in focal stroke.

Animals↗
PubMed1994

SB 209670, a rationally designed potent nonpeptide endothelin receptor antagonist.

An extremely potent and highly specific non-peptide, subnanomolar endothelin (ET) receptor antagonist, SB 209670, has been synthesized and characterized. SB 209670, which was rationally designed using conformational models of ET-1, selectively inhibits binding of 125I-labeled ET-1 to cloned human ET receptor subtypes ETA and ETB (Ki = 0.2 and 18 nM, respectively). SB 209670 produces concentration-dependent inhibition of ET-1-mediated vasoconstriction in isolated vascular tissues and in vivo following either intravenous or intraduodenal administration. SB 209670 produces a dose-dependent reduction in blood pressure in hypertensive rats, protects from ischemia-induced neuronal degeneration in a gerbil stroke model, and attenuates neointima formation following rat carotid artery balloon angioplasty. SB 209670 will be useful in characterizing and classifying the physiological and pathophysiological effects of ET.

Animals↗
PubMed1994

Tyr-129 is important to the peptide ligand affinity and selectivity of human endothelin type A receptor.

Molecular modeling and protein engineering techniques have been used to study residues within G-protein-coupled receptors that are potentially important to ligand binding and selectivity. In this study, Tyr-129 located in transmembrane domain 2 of the human endothelin (ET) type A receptor A (hETA) was targeted on the basis of differences between the hETA and type B receptor (hETB) sequences and the position of the residue on ET receptor models built using the coordinates of bacteriorhodopsin. Replacement of Tyr-129 of hETA by alanine, glutamine, asparagine, histidine, lysine, serine, or phenylalanine results in receptor variants with enhanced ET-3 and sarafotoxin 6C affinities but with unchanged ET-1 and ET-2 affinities. Except for Tyr-129-->Phe hETA, these hETA variants have two to three orders of magnitude lower binding affinity for the ETA-selective antagonist BQ123. Replacement of His-150, the residue in hETB that is analogous in sequence to Tyr-129 of hETA, by either tyrosine or alanine does not affect the affinity of peptide ligands. These results indicate that although transmembrane domain 2 is important in ligand selectivity for hETA, it does not play a significant role in the lack of ligand selectivity shown by hETB. Chimeric receptors have been constructed that further support these conclusions and indicate that at least two hETA regions contribute to ligand selectivity. Additionally, the data support an overlap in the binding site in hETA of agonists ET-3 and sarafotoxin 6C with that of the antagonist BQ123.

Animals↗
PubMed1994

Functional evidence that balloon angioplasty results in transient nitric oxide synthase induction.

Since serious vasospastic episodes limit the efficacy of percutaneous transluminal coronary angioplasty, this study has examined the time-dependent changes in vascular reactivity that occur following rat carotid artery balloon angioplasty. Relative to vessels from sham-operated animals, angioplasty caused an immediate increase in endothelin-1 contractile potency, an observation not made with noradrenaline or KCl, implicating endothelin-1 in the pathogenesis of acute arterial vasospasm. This hyperreactivity, possibly resulting from the loss of endothelin-1-induced nitric oxide release from the endothelium, was transient and was followed by a non-specific decrease in reactivity to all three spasmogens. Since the delayed reduction in endothelin-1 contractile potency was restored by N omega-nitro-L-arginine methyl ester, this hyporeactivity appeared to result from nitric oxide synthase induction. Furthermore, since the regenerating endothelium was dysfunctional, the generation of nitric oxide was from a non-endothelial source (possibly the smooth muscle or infiltrating macrophages). This response may function to ameliorate the spasmogenic and proliferative actions of chronically acting vasoactive factors and oppose platelet aggregation.

Amino Acid Oxidoreductases↗
PubMed1994

Osteopontin-stimulated vascular smooth muscle cell migration is mediated by beta 3 integrin.

Osteopontin (OPN), a 41-kDa phosphorylated glycoprotein, has been detected in rat aorta and carotid arteries, and expression of its mRNA in blood vessels is strongly increased in response to vascular injury. To investigate the potential role of OPN in vascular pathophysiology, we studied the effect of rat OPN on aortic smooth muscle cell migration and proliferation in vitro. OPN enhanced the migration of rat smooth muscle cells in a time- and concentration-dependent manner with an EC50 value of 46 +/- 11 nmol/liter (n = 5). The maximal increase in cell migration by OPN was 29-fold over basal levels. OPN-induced smooth muscle cell migration was inhibited in a concentration-dependent manner by the monoclonal antibody F11, which recognizes the rat integrin subunit beta 3. In contrast, polyclonal antiserum recognizing the rat integrin beta 1 subunit did not inhibit smooth muscle cell migration in response to OPN, but did block fibronectin-promoted migration. Moreover, OPN-induced smooth muscle cell migration was dependent on the presence of extracellular divalent cations and was significantly inhibited by anti-OPN antibodies. OPN did not stimulate [3H]thymidine incorporation into cultured smooth muscle cells, indicating that it selectively enhanced migration. In view of the pathological significance of arterial smooth muscle cell migration in the formation of intimal thickening, our results suggest that smooth muscle cell recognition of OPN, probably through the vitronectin receptor, alpha v beta 3, could play a role in the cells' response to vascular injury and especially neointima formation.

Animals↗
PubMed1994

Human laminin produces human platelet aggregation in vitro.

The effects of laminin isoforms on platelet aggregation were compared and characterized in platelet rich plasma (PRP) obtained from 26 healthy human volunteers. In approximately 38% of the individuals tested, human laminin produced a biphasic platelet aggregation response. Human laminin produced only a primary phase in the remaining "non-responsive" individuals. Mouse laminin, rat laminin and human merosin did not cause platelet aggregation in any of the volunteers. The biphasic platelet aggregation response caused by human laminin was concentration-dependent (0.3-30 nM) and was consistently observed upon repeated testing of "responsive" individuals. The secondary phase of aggregation produced by human laminin in "responsive" individuals was abolished by aspirin, SQ 29,548, a selective thromboxane antagonist, and SK&F 106760, an RGD-derived platelet fibrinogen receptor (GPIIb/IIIa) antagonist. Also, the secondary phase of aggregation was not observed in washed platelets. Both the primary and secondary platelet responses produced by human laminin were abolished by a VLA-6 (alpha 6 beta 1) monoclonal antibody, but not by the YIGSR pentapeptide. In conclusion, human laminin causes thromboxane-dependent platelet aggregation, in vitro, in a significant population of human volunteers. The aggregation response was dependent upon the interaction of human laminin with platelet VLA-6 (alpha 6 beta 1). These novel results suggest that in some individuals laminin may play an important role in hemostasis and thrombogenesis.

Adult↗