Canine Femoral Veins Research Articles

Selective isolation of vein graft endothelial and smooth muscle cells using laser capture microdissection for microarray gene analysis

Our study employed laser capture microdissection to selectively collect endothelial (EC) and smooth muscle cells (SMC) from patent canine femoral artery bypass cephalic vein grafts (n=3) and normal contralateral cephalic vein controls (harvested after 24 hours). Total RNA was purified, converted to cDNA, and prepared for Affymetrix Canine 2.0 GeneChip hybridization (43,036 probes, 16,984 genes). Sample purities were measured via qRT‐PCR (EC: CD31, eNOS, vWF; SMC: α‐actin 2, SMC‐MHCII). Chip normalization and analysis were executed with BioConductor and dChip. Significantly up‐ (UR) or downregulated (DR) graft genes had =2.0 fold change versus control and absolute lower confidence bound of =2.0. Human genes were matched using BLAST PERL. Average isolate purities were 43‐78% for EC and 79‐100% for SMC. In grafts versus controls, 2101 genes were differentially expressed in EC and 1753 in SMC. UR genes: 1112 in EC, 729 in SMC, 322 in common. DR genes: 989 in EC, 1024 in SMC, 444 in common. Clustering analysis showed unique clustering of graft versus control EC and SMC. Gene ontology analysis exhibited predominant gene functions in protein binding (EC & SMC), cellular processes involved in inflammation (EC) and cell motility (SMC) and localizations to the plasma membrane (EC) and ECM (SMC). LCM is effective in separating gene responses in the intima from the media of vein grafts. NIH 5 T32 HL007734 & 5 R01 HL086741 to FWL

Normal and perturbed endothelial cells from canine femoral arteries and femoral veins exhibit heterogeneity in hemostatic properties and growth characteristics.

We sought to examine the heterogeneity of endothelial cells from the same anatomic site but different vascular systems and described von Willebrand factor (vWF) release and morphological change in response to injury-associated factor in femoral vessels from canine in vitro. Levels of hemostatic factors (vWF, plasminogen activator inhibitor type 1(PAI-1), antithrombin III (ATIII), in tissue sections and cultured endothelial cells of canine femoral arteries and canine femoral veins were compared by the immunohistochemistry technique. In addition to comparing cell growth density and cell protein contents, cultured femoral arterial endothelial cells (FAECs) and cultured femoral venous endothelial cells (FVECs) were incubated with a series concentration of basic fibroblast factor (bFGF) (1, 10, 100 ng/ml) for up to 48 hours to test the amount of vWF secretion and morphological change. Both in tissue sections and cultured cells, the levels of vWF are higher in FVECs than in FAECs. We were unable to differentiate the level of PAI-1 and ATIII difference between FAECs and FVECs. bFGF (10 ng/ml) significantly increased vWF secretion from cultured FAECs but not from FVECs. The size of cultured FAECs is smaller than of FVECs; however, FAECs have higher amounts of protein contents than FVECs. These comparative studies provide evidence indicating that the characteristics of FVECs differ from those of FAECs. These differences may be indicated heterogeneity with either inherited or acquired thrombotic disease.

Specific determination of endothelial cell viability in the whole cell fraction from cryopreserved canine femoral veins using flow cytometry.

Abstract: An efficient method for specifically determining the viability of endothelial cells (EC) from cells dissociated from the human saphenous vein was investigated. Three different methods, trypan blue staining assay, [3H]-proline incorporation assay, and flow cytometry (FCM), combined with the fluorescein isothiocyanate conjugated with Griffonia simplicifolia agglutins (GS1-FITC)/propidium iodide (PI) double staining, were used. Both trypan blue staining and [3H] proline incorporation assays demonstrated less sensitivity to determine viability of EC differentially from the other cells. FITC-GS1 showed prominent binding to the vascular EC and could be counted by FCM including PI on dead cells. Following the cryopreservation process, the GS1-FITC/PI FCM analytical method was adopted to test simultaneously the viability of whole cells and EC from the same tissue, human saphenous veins, and mongrel dogs' femoral veins after harvesting, antibiotic solution treatment, and thawing. The viability of the whole cells from veins decreased with a significant difference (p < 0.05) from that of EC after thawing.

Activation of soluble guanylate cyclase and potassium channels contribute to relaxations to nitric oxide in smooth muscle derived from canine femoral veins.

Experiments were designed to examine mechanisms of relaxations to nitric oxide (NO) in venous smooth muscle. Rings of canine femoral veins without endothelium were suspended for measurement of isometric force in organ chambers. Concentration-response curves to NO and 8-Br-cyclic guanosine monophosphate (cGMP) were obtained in veins contracted with KCl (60 mM) or prostaglandin F2alpha (PGF2alpha; 2x10(-6) M) in the absence and presence of inhibitors of soluble or particulate guanylate cyclase or K+ channel antagonists. In rings contracted with PGF2alpha, relaxations to NO were reduced significantly by inhibition of soluble but not particulate guanylate cyclase. Relaxations to NO were reduced in rings contracted with KCI. Tetraethylammonium (10(-2) M) and glibenclamide (10(-7) M) + charybdotoxin (10(-7) M) significantly reduced relaxations to NO in rings contracted with PGF2alpha. Relaxations to 8-Br-cGMP were decreased significantly only by charybdotoxin. These results suggest that relaxations to NO in canine femoral veins involve at least two intracellular processes: activation of soluble guanylate cyclase and activation of adenosine triphosphate (ATP)-sensitive and large-conductance, Ca+2-activated K+ channels. The large-conductance, Ca+2-activated K+ channels seem to be activated by cGMP-dependent mechanisms. Therefore relaxations to NO in venous smooth muscle involve intracellular processes similar to those in arterial smooth muscle.

Experimental evaluation of four methods of progressive venous attenuation in dogs.

To determine the most effective and reliable method for progressive attenuation of single extrahepatic portosystemic shunts in dogs. The effects of the four treatments on femoral vein diameter and histology were compared with controls. Fourteen healthy adult dogs. Twenty-eight canine femoral veins were subjected to sham surgery (4), partial attenuation using silk (5), cellophane banding (6), ameroid constrictor implantation (5), and intravascular thrombogenic coils (8). Changes in vein diameter were evaluated at weekly intervals using venography. After 6 weeks, the dogs were humanely euthanatized, and histopathology was performed on the femoral veins. Only cellophane and ameroid constrictors produced progressive and permanent vein attenuation. Ameroid constrictors produced complete occlusion within 14 days in four of five veins and by 21 days in the fifth vein. Cellophane banding produced slow progressive (but not complete) attenuation in five of six veins. Complete occlusion was demonstrated in four of eight veins after thrombogenic coil implantation; however, recanalization occurred in all but one dog. Perivascular silk did not produce significant progressive attenuation. Ameroid constrictors produced rapid occlusion of femoral veins. Cellophane banding resulted in slower attenuation. Thrombogenic coils produced attenuation, but this was not sustained in many cases. Silk did not promote ongoing attenuation. Both ameroid constrictor implantation and cellophane banding show promise for progressive attenuation of single extrahepatic portosystemic shunts in dogs. Because rapid occlusion was seen with ameroid constrictors, however, cellophane banding maybe a safer technique in animals with increased hepatic vascular resistance. Further evaluation of both treatments in clinical cases is warranted.

Postsurgical changes of the opening angle of canine autogenous vein graft.

The opening angles of 30 canine autogenous vein grafts were measured to determine the postsurgical change of residual strain in the vein graft. Canine femoral veins were grafted to femoral arteries in the end-to-end anastomosis fashion. When harvested, the vein grafts were cut into short segments and the segments were cut open radially. The opened-up configurations were taken as the zero-stress states of the vessels. Opening angle, defined as the angle between the two lines from the middle point to the tips of the inner wall, was used to describe the zero-stress states. Results show that the opening angles (mean +/- SD) are 63.0 +/- 30.6 deg for normal femoral veins, and -0.4 +/- 4.6, 6.1 +/- 19.4, 25.4 +/- 20.1, and 47.8 +/- 11.4 deg for vein grafts at 1 day, 1 week, 4 and 12 weeks postsurgery, respectively. The postsurgical changes in opening angle reveal nonuniform transmural tissue remodeling in the vascular wall. The relations between the changes in opening angle and the changes in the morphology of the vein grafts are discussed. Intimal hyperplasia is correlated to the opening angle and is suggested to be the main factor for the postsurgical increase in opening angle. The longitudinal strain in the vein graft is found to decrease postsurgically.

Photo-Oxidized Bovine Arterial Grafts Short-Term Results

Biologic grafts are the conduit of choice for vascular reconstructive procedures. The short-term thrombogenicity, patency, and stability of bovine arterial grafts, altered by a dye-mediated photo-oxidation process, was evaluated in the canine common femoral vein (CFV) and artery (CFA) model. Modified bovine interposition grafts were implanted in the CFV of 12 dogs and in the CFA of 11 dogs, respectively. Polytetrafluoroethylene (PTFE) implants on the contralateral side served as controls. Patency and histology were assessed at 1, 2, 4, and 6 weeks. In the CFV, patency of photo-oxidized grafts was 83% at 1 week and 71% at 2 weeks, compared to 17% and 0% for PTFE, respectively (p = 0.0033). In CFA, patency was 82% for the photo-oxidized graft and 63% for PTFE at 6 weeks (p = NS). Photo-oxidized grafts were nonreactive, without evidence of degenerative changes or cellular infiltration at all time periods. Compared to commercially available PTFE, photo-oxidized arterial grafts have superior patency in the CFV, and comparable patency in the CFA. Preliminary results demonstrate that these xenografts are stable and without degenerative changes. If corroborated by long-term data, these grafts may be a suitable alternative to currently available prosthetics for peripheral vascular reconstructive procedures.

Adrenomedullin-Mediated Relaxations in Veins are Endothelium-Dependent and Distinct from Arteries

In arteries, adrenomedullin (ADM) causes relaxations of rings with and without endothelium by stimulating accumulation of cyclic nucleotides resulting from activation of the ADM and calcitonin gene-related peptide (CGRP) receptors. Experiments were designed to determine the mechanism(s) of relaxation to ADM in veins. Rings of canine femoral vein with and without endothelium were suspended in organ chambers for measurement of isometric force. Rings were contracted with prostaglandin F2alpha (2 x 10(-6) M), and cumulative dose-responses to ADM (10(-11) to 10(-7) M) were obtained in the absence or presence of indomethacin (10(-5) M), indomethacin + N(G)-monomethyl-L-arginine (10(-4) M), methylene blue (10(-5) M), particulate guanylate cyclase inhibitor HS-142-1 (10(-5) M), tetraethylammonium (TEA, 10(-2) M), CGRP-receptor antagonist (CGRP 8-37, 10(-6) M), ADM-receptor antagonist (ADM 26-52, 10(-6) M), diphenhydramine (10(-6) M), 8-phenyltheophylline (3 x 10(-6) M), or superoxide dismutase (150 U/ml) plus catalase (1,200 U/ml). ADM produced concentration-dependent relaxations only in veins with endothelium. Relaxations to ADM in rings with endothelium were significantly inhibited only by methylene blue and HS-142-1. In separate experiments, incubation of rings with ADM (10(-8) M) and 3-isobutyl-1-methyl-xanthine (10(-4) M) for 3 min did not significantly affect the accumulation of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP). These data suggest that ADM-mediated relaxation in veins is endothelium dependent and is not associated with activation of CGRP receptors or currently defined ADM receptors. Further, relaxations are not mediated by nitric oxide, indomethacin-sensitive prostanoids, TEA-sensitive hyperpolarizing factors, oxygen free radicals, or accumulation of cyclic nucleotides.

Effects of serotonin and endothelin on the smooth muscle cells of autogenous vein grafts

The purpose of this study was to compare the effects of vasoconstrictor substances such as 5-hydroxytryptamine (5-HT) and endothelin on the smooth muscle of canine femoral veins and vein grafts. The right canine femoral vein was grafted into the right femoral artery. The left femoral vein was used as a control. In other experiments to examine the effects of surgical procedures such as dissection of the adventitia and the effects of grafting (vein-to-vein bypass), the right femoral vein was dissected out but not removed for grafting and an autogenous vein bypass of the right femoral vein was made using the left femoral vein. In all experiments, the veins were removed 4 weeks after operation and suspended in organ chambers for isometric tension recording. Maximum contractions to endothelin were comparable in control vein and vein grafts. In control vein, the maximum contraction to 5-HT was small, and was inhibited by both methiothepin, a 5-HT, and 5-HT2 antagonist, and sarpogrelate hydrochloride, a 5-HT2 antagonist. In vein grafts 5-HT produced significantly larger contractions than in control veins, which were inhibited by methiothepin but not by the 5-HT2 antagonist. In veins with adventitial dissection alone and vein-to-vein grafts, 5-HT produced small contractions which were comparable to those in control vein. The larger contraction response to 5-HT in canine vein grafts may be due to an increased responsiveness of the 5-HT1 receptor caused by grafting into the arterial circulation.

An arginine analog inhibits responses of both the endothelium and smooth muscle of canine in situ vein grafts

Increased shear, pressure, and oxygen tension in vein grafts may alter production of endothelium-derived vasoactive and anti-mitogenic factors such as nitric oxide which subsequently affect development of neointimal hyperplasia. This study was designed to determine whether or not nitric oxide mediates endothelium-dependent responses in femoral in situ vein grafts. Non-reversed, canine femoral vein grafts were placed bilaterally to bypass a ligated segment of the femoral artery in dogs. After 6 weeks, the grafts were removed, cut into rings, and suspended in organ chambers for measurement of isometric force. In some rings the endothelium was removed deliberately. In the presence of indomethacin, the synthetic analog of l-arginine, l-N G-monomethyl-arginine (10 −4 M; l-NMMA) did not cause a significant change in baseline tension of rings with endothelium. l-NMMA reduced only contractions of rings with endothelium to the alpha-adrenergic agonist UK 14,304. The analog also reduced maximal relaxations to the calcium-ionophore, A23187 in rings with endothelium. In addition, l-NMMA reduced relaxations of rings without endothelium to adenosine diphosphate by 35%. Positive immunostaining for nitric oxide synthase was present in both the myointima and media of histological sections of grafts. In conclusion, these results suggest that in situ vein grafts exhibit two unique properties which are unlike unoperated arteries or veins: (i) alpha 2-adrenergic receptors may be coupled to the release of contractile endothelium-derived factors associated with production of nitric oxide; and (ii) nitric oxide may be released by the smooth muscle in response to purinergic stimulation. The presence of nitric oxide synthase throughout the wall of the graft may result in production of nitric oxide in response to adenosine diphosphate released by platelets and to circulating catecholamines. © 1997 The International Society for Cardiovascular Surgery.

An Arginine Analog Inhibits Responses of Both the Endothelium and Smooth Muscle of Canine in situ Vein Grafts

Increased shear, pressure, and oxygen tension in vein grafts may alter production of endothelium-derived vasoactive and anti-mitogenic factors such as nitric oxide which subsequently affect development of neointimal hyperplasia. This study was designed to determine whether or not nitric oxide mediates endothelium-dependent responses in femoral in situ vein grafts. Non-reversed, canine femoral vein grafts were placed bilaterally to bypass a ligated segment of the femoral artery in dogs. After 6 weeks, the grafts were removed, cut into rings, and suspended in organ chambers for measurement of isometric force. In some rings the endothelium was removed deliberately. In the presence of indomethacin, the synthetic analog of L-arginine, L-NG-monomethyl-arginine (10−4 M: L-NMMA) did not cause a significant change in baseline tension of rings with endothelium. L-NMMA reduced only contractions of rings with endothelium to the alpha-adrenergic agonist UK 14,304. The analog also reduced maximal relaxations to the calcium-ionophore, A23187 in rings with endothelium. In addition, L-NMMA reduced relaxations of rings without endothelium to adenosine diphosphate by 35%. Positive immunostaining for nitric oxide synthase was present in both the myointima and media of histological sections of grafts. In conclusion, these results suggest that in situ vein grafts exhibit two unique properties which are unlike unoperated arteries or veins: (i) alpha2-adrenergic receptors may be coupled to the release of contractile endothelium-derived factors associated with production of nitric oxide; and (ii) nitric oxide may be released by the smooth muscle in response to purinergic stimulation. The presence of nitric oxide synthase throughout the wall of the graft may result in production of nitric oxide in response to adenosine diphosphate released by platelets and to circulating catecholamines.

Mechanism of relaxations to C-type natriuretic peptide in veins.

C-type natriuretic peptide (CNP) is an endothelium-derived peptide that shares structural homology with atrial natriuretic peptide (ANP). CNP causes greater endothelium-independent relaxations in veins compared with arteries. Relaxations to CNP in porcine coronary arteries are mediated by hyperpolarization of the smooth muscle membrane. Experiments were designed to investigate the mechanism(s) by which CNP causes relaxation in canine femoral veins. Rings of canine femoral veins without endothelium were suspended for measurement of isometric force in organ chambers. Concentration-response curves to CNP were obtained in veins contracted with either endothelin-1 (10(-8) M), KCl (40 mM), phenylephrine (10(-6) M) or prostaglandin F2 alpha (2 x 10(-6) M) in the absence and presence of BQ-123 (10(-6) M), NG-monomenthyl-L-arginine (L-NMMA; 10(-4) M), HS-142-1 (10(-5) M), methylene blue (10(-5) M), or potassium channel blockers, tetraethylammonium chloride (TEA; 10(-3) M), charybdotoxin (10(-7) M), glibenclamide (10(-7) M), or apamin (10(-7) M). Relaxations to CNP were significantly attenuated when the tissue was contracted with KCl and endothelin-1. During contraction to either phenylephrine or prostaglandin F2 alpha, relaxations to CNP were inhibited by HS-142-1, methylene blue, TEA, and charybdotoxin, but not by L-NMMA, glibenclamide, or apamin. In separate experiments, guanosine 3',5'-cyclic monophosphate increased twofold within 10-60 s after the addition of CNP (10(-8) M). These data suggest that CNP mediates relaxation of canine femoral veins through activation of large-conduction, calcium-activated potassium channels and activation of particulate and soluble guanylate cyclase.

Biocompatibility of sulphonated polyurethane surfaces

Surfaces of medical devices made of polymeric materials may promote thrombosis and inflammation. Therefore, in an attempt to produce surfaces which might diminish biomaterial-mediated thrombosis and inflammation, surface derivatization with 2-acrylamido-2-methylpropanesulphonic acid (AMPS®) was carried out. The derivatization procedure generates free radicals which initiate the copolymerization of AMPS monomers directly to a polyurethane surface. In an in vitro blood loop study using non-anticoagulated human blood, the resulting AMPS-derivatized material completely abrogates the generation of fibrinopeptide A, decreases the production of β-thromboglobulin and C3a, and decreases the adherence of platelets. The derivatized material also attracts fewer adherent neutrophils when implanted in mice. However, AMPS derivatization unexpectedly increases the recruitment of macrophages to implanted material and promotes the formation of adherent sleeve thrombi on central venous catheters indwelling in non-anticoagulated canine femoral veins. Thus, AMPS derivatization has highly variable effects on inflammatory and thrombotic systems. Further investigation is clearly required to determine the mechanisms underlying both desired and adverse effects.

Modulation of endothelium-derived nitric oxide in canine femoral veins.

Experiments were designed to determine whether nitric oxide was the mediator of increased endothelium-dependent relaxations in veins proximal to an arteriovenous fistula. A fistula was prepared between femoral arteries and veins in dogs. After 6 wk, veins proximal to the fistula were removed, cut into rings, and suspended for the measurement of isometric force in organ chambers. In some rings the endothelium was removed deliberately. NG-monomethyl-L-arginine (L-NMMA) caused contraction in three of six fistula-operated veins with and without endothelium. In rings contracted submaximally with prostaglandin F2 alpha, acetylcholine and the alpha 2-adrenergic agonist UK-14,304 cause e tylcholine and the alpha 2-adrenergic agonist UK-14,304 caused endothelium-dependent, concentration-dependent relaxations that were greater in fistula compared with sham-operated veins. These relaxations were reduced by L-NMMA. Calcium ionophore A23187 caused comparable endothelium-dependent relaxations in fistula- and sham-operated veins that were unaffected by L-NMMA. There were no differences in either calcium-dependent or -independent activity of nitric oxide synthase isolated from fistula- and sham-operated veins. Positive staining for nitric oxide synthase was present in both the endothelium and media of fistula-operated veins. These results indicate that nitric oxide mediates increased endothelium-dependent relaxations to acetylcholine and alpha 2-adrenergic agonists in fistula-operated veins. Therefore, chronic increases in blood flow and oxygen tension modify selectively receptor-coupled production of nitric oxide in endothelium and smooth muscle of veins.

Transgraft Infusion of Heparin to Prevent Early Thrombosis of Expanded PTFE Grafts in Canine Femoral Veins

Recently we designed an expanded polytetrafluoroethylene (ePTFE)-based local infusion device that delivers therapeutic agents directly through the graft wall in the region adjacent to the upstream anastomosis, thereby achieving a high drug concentration downstream along the graft-blood interface. In this study we evaluated the effects of infusing heparin by this method on graft patency and neointimal hyperplasia in a canine model of femoral vein replacement. Five dogs underwent bilateral femoral vein replacement with the device. In each case one graft was infused with continuous heparin (48 U/kg/day) while the contralateral control graft received phosphate-buffered saline solution for 14 days. All heparin-treated grafts were patent and all control grafts were thrombosed at 14 days. There was no significant difference in systemic activated partial thromboplastin time among samples taken preoperatively, at 48 hours, and at 14 days of implantation (p > 0.5). There was no significant difference in neointimal hyperplasia between the upstream and downstream anastomoses in heparin-treated grafts. These data demonstrate that the transgraft infusion of heparin preserved venous ePTFE graft patency without measurable systemic anticoagulation. Thus this approach may represent an attractive strategy for maintaining patency of synthetic venous grafts.

Modulation of contractions to and receptors for endothelins in canine veins.

Experiments were designed to characterize endothelin receptors in canine femoral veins and to determine whether their distribution or sensitivity could be altered by chronic changes in blood flow and oxygen tension in veins proximal to an arteriovenous fistula. Endothelium was removed from unoperated or fistula-operated femoral veins of anesthetized dogs. Veins were cut into rings and suspended in organ chambers for the measurement of isometric force or frozen for isolation of membrane proteins. Endothelin-1, endothelin-3, and sarafotoxin S6c caused concentration-dependent increases in tension in all rings. In rings of unoperated veins, maximal tensions were significantly less to endothelin-3 and sarafotoxin S6c than to endothelin-1. In rings of fistula-operated veins, maximal tensions to endothelin-1 and endothelin-3 were the same. Contractions to endothelin-1 or endothelin-3 in unoperated veins were not inhibited by an antagonist of endothelin-A receptors, BQ-123. Binding of 125I-labeled endothelin-1 (125I-endothelin-1) to membranes from veins without endothelium increased as a function of membrane protein. Affinity of receptors, as determined by competitive inhibition of 125I-endothelin-1 was as follows: endothelin-1 > endothelin-3 > sarafotoxin S6c. Competitive inhibition of 125I-endothelin-1 by endothelin-3 and sarafotoxin S6c was significant for a two-site binding model in all veins. The total number of binding sites was reduced significantly in fistula-operated veins; the relative proportions of high- and low-affinity binding sites did not change. Affinity of high- and low-affinity receptors increased in fistula-operated veins.(ABSTRACT TRUNCATED AT 250 WORDS)

The contractile mechanism of beraprost sodium, a stable prostacyclin analog, in the isolated canine femoral vein.

The vascular contractile mechanism of prostacyclin (PGI2) was investigated using beraprost sodium (BPS), a stable PGI2 analog. Ring strips without endothelium isolated from canine femoral veins and arteries were used. BPS induced a dose-dependent contraction without precontraction and after precontraction with norepinephrine (NE) or 60 mM K+ in the veins. In contrast, BPS induced a dose-dependent relaxation after precontraction with U46619, a thromboxane A2 (TXA2) analog, or prostaglandin F2 alpha (PGF2 alpha) in the veins. In the arteries, BPS induced contraction at higher concentrations after precontraction with NE. However, BPS relaxed arteries dose-dependently after precontraction with PGF2 alpha. By pretreatment with 13-azaprostanoic acid (13-APA), a TXA2/endoperoxide receptor antagonist, the dose-response curve of BPS in the veins was shifted to the right. Schild plot analysis resulted in a linear regression with a slope of 0.86 +/- 0.13, which was not significantly different from unity, and the pA2 value for 13-APA against BPS was 7.10 +/- 0.06. By pretreatment with BPS, the dose-response curve of U46619 in the veins was shifted to the right. Kaumann plot analysis resulted in a linear regression with a slope of 0.89 +/- 0.09, which was not significantly different from unity, and the pA2 value for BPS against U46619 was 5.68 +/- 0.04. These findings indicate that BPS is a partial agonist for the TXA2/endoperoxide receptors.

O-14 - Differential action of dopamine (DA) on canine femoral arteries and veins, and the mechanism of its action.

O-14 - Differential action of dopamine (DA) on canine femoral arteries and veins, and the mechanism of its action.

Cofactors of constitutive nitric oxide synthase and endothelium-dependent relaxations in canine femoral veins.

Enzymatic production of nitric oxide (NO) in arterial endothelial cells requires the cofactors calmodulin and nicotinamide adenine dinucleotide phosphate (NADPH). Experiments were designed in investigate whether these cofactors are required for endothelium-dependent relaxations in canine femoral veins. Veins were removed from anesthetized dogs and cut into rings. Endothelium was deliberately removed from some rings. All rings were incubated with indomethacin (1 x 10(-5) M). In separate sets of experiments, rings were incubated with calmidazolium (1 x 10(-5) M), fendiline (1 x 10(-6) M), both inhibitors of calmodulin or diphenylene-iodonium (1 x 10(-5) M; DPI) an inhibitor of NADPH. Concentration-response curves were obtained for acetylcholine (ACh), ADP, thrombin, A23187, and NO in rings contracted with a submaximal concentration of prostaglandin F2 alpha (PGF2 alpha) in the presence of the inhibitors and compared with a solvent control (dimethyl sulfoxide, DMSO). Relaxations to ACh, ADP, and thrombin were reduced by the inhibitors of both cofactors. Relaxations to A23187 were reduced by inhibitors of calmodulin but not NADPH; inhibitors of both NADPH and calmodulin caused no significant reduction in relaxations to NO. These data suggest that endothelium-dependent relaxations in canine femoral veins are mediated by factor(s) that are partly dependent on calmodulin or NADPH as cofactors for their production or release.

Angioscope-Assisted Endovascular Occlusion of Venous Tributaries: Preclinical Studies

The feasibility of angioscope-assisted occlusion of venous tributaries from within a vein using a steerable 'shaped-memory' nickel-titanium (nitinol) alloy catheter and occlusion coils was evaluated. An initial series of tests was designed to establish the necessary pressure (275 p.s.i., 1897.5 kPa), time (1.5 s) and volume (2.5 ml normal saline) requirements for hydraulic delivery of platinum occlusion coils from the nitinol catheter through a 3-Fr tracking catheter. In a second series, 25 side branches of the saphenous vein in 11 amputated limbs were visualized angioscopically and cannulated with the nitinol catheter under angioscopic and fluoroscopic surveillance to determine whether the catheter tip could be positioned and coils deployed. In a third series of studies, ten canine femoral vein tributaries were successfully cannulated with an 8-Fr nitinol catheter and 19 occlusion coils delivered under angioscopic surveillance. Fluoroscopy verified coil placement and all embolized venous tributaries were thrombosed. An ideal approach for femoropopliteal in situ saphenous vein bypass would allow the surgeon to divide saphenous vein valves while occluding venous side branches from within the saphenous vein. These initial studies demonstrate that the nitinol catheter can occlude venous tributaries from within a vein by coil embolization. Further development of this technique for clinical investigation is warranted.