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PubMed1998

Regulation of the vasomotor activity of lymph microvessels by nitric oxide and prostaglandins.

It was shown previously that the presence of endothelium modulates spontaneous vasomotion of small lymphatic vessels. In the present study, we aimed to elucidate the nature of endothelium-derived factors, produced in basal conditions and in response to agonists, that affect the smooth muscle tone of lymph microvessels in vitro. Afferent lymph microvessels were isolated from rat iliac lymph nodes, cannulated with glass micropipettes, and pressurized (6 cmH2O), and changes in their diameter were investigated with video microscopy. In resting conditions, isolated lymph vessels exhibited spontaneous constrictions and dilations. The maximum and minimum diameters (Dmax and Dmin) were 149.8 +/- 2.9 and 85.8 +/- 3.6 microns, respectively. Acetylcholine (ACh, 10(-7) to 10(-5) M) and sodium nitroprusside (SNP, 10(-8) to 10(-6) M) temporarily abolished diameter oscillations, increasing the diameter of lymphatics dose dependently. For example, 10(-5) M ACh and 10(-6) M SNP increased the diameter (Dmax) by 15.2 +/- 2.2 and 25.0 +/- 2.7 microns, respectively. Treatment of vessels with NG-nitro-L-arginine (10(-4) M) significantly reduced the amplitude of diameter oscillations and nearly completely eliminated ACh-induced dilation of lymph microvessels, whereas SNP (10(-6) M) elicited a significantly greater dilation (55.6 +/- 7.5 microns). Arachidonic acid (AA, 10(-8) to 10(-6) M) constricted (up to 50 microns), whereas prostaglandin E2 (PGE2, 10(-9) to 10(-7) M) dilated (up to 40 microns), lymphatic vessels. Indomethacin (10(-5) M) increased both Dmax and Dmin and completely inhibited AA-induced constrictions, but did not affect PGE2-induced dilations of lymph microvessels. AA-induced constrictions of lymphatics were converted into dilations after treatment with SQ-29,548, a selective PGH2-thromboxane A2 (PGH2-TxA2, 10(-6) M) receptor antagonist, whereas PGE2-induced dilations were not affected. We conclude that endothelial nitric oxide and prostaglandins are important modulators of lymphatic vasomotion, hence pumping activity of lymph microvessels in vivo.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1988

A rapid method for isolating rabbit renal microvessels.

A technique has been described to isolate rabbit renal preglomerular microvessels using an infusion of a magnetized iron oxide suspension into the renal artery. An initial separation of the vascular tissue was performed with a magnet and a final separation was performed using a nylon sieve allowing nonvascular, tubular, and glomerular contaminants to be filtered free from the microvessels. Light and electron microscopy showed morphology consistent with interlobular arteries and afferent arterioles. The purity of the preparation was greater than 95%. In the absence of exogenous arachidonic acid, the microvessels were able to synthesize prostacyclin (7.5 +/- 1.2 ng.mg protein-1.min-1) in excess of prostaglandin E2 (2.2 +/- 0.7 ng.mg protein-1.min-1). The tissue exhibited a time-dependent increase in prostanoid biosynthesis up to 60 min and responded to stimulators (e.g., melittin and arachidonic acid) and inhibitors (e.g., meclofenamate and indomethacin) of prostanoid biosynthesis. These studies indicate that a high-yielding and versatile preparation of renal preglomerular microvessels can be rapidly obtained. The microvessels are viable and may represent an excellent model for studying a variety of biochemical interactions under in vitro conditions.

Animals↗

PubMed1994

Endothelial cell hyperpolarization increases [Ca2+]i and venular microvessel permeability.

We tested the hypothesis that Ca2+ influx into endothelial cells forming the walls of intact venular microvessels was increased when the cell membranes were hyperpolarized. Cytoplasmic free Ca2+ concentration ([Ca2+]i) was measured after the endothelial cells forming the microvessel wall were loaded with fura 2, endothelial cell membrane potential was measured with the membrane potential dye bis-oxonol, and hydraulic conductivity (Lp) of the vessels was measured by the modified Landis technique to follow changes in microvessel permeability. When microvessels were exposed to low-K+ (0.1 mM) Ringer solution, the membrane of the endothelial cells was hyperpolarized approximately 27 mV and [Ca2+]i increased from 47 nM to a peak value of 151 +/- 28 nM. Under the same experimental conditions, Lp increased to a peak 6.3 times control. In the presence of ionomycin (5 microM), the initial peak [Ca2+]i measured with low-K+ Ringer solution was 347 +/- 58 nM compared with 252 +/- 58 nM with ionophore and normal Ringer solution. The corresponding initial increases in Lp were 28 times control and 10 times control, respectively. The results conform to the hypothesis that vasoactive substances that hyperpolarize the endothelial cell membrane may initiate and/or potentiate the inflammatory response in venular microvessels.

Animals↗

PubMed2004

Relation between serum anti-p53 antibodies and microvessel density in bladder cancer patients.

INTRODUCTION: Etiology of serum anti-p53 antibodies in bladder cancer patients is still unknown. In this study we evaluated the relationship between serum anti-p53 antibodies and microvessel density in bladder cancer patients. MATERIALS AND METHODS: Seventy-six patients with transitional cell carcinoma of the urinary bladder were assessed prospectively (18 Ta, 30 T1, 28 T2>or =). Serum anti-p53 antibodies were detected by enzyme-linked immunosorbent assay. Tumor p53 overexpression was assessed by immunohistochemical staining. Vessels were stained immunohistochemically using an antibody against platelet endothelial cell-adhesion molecule CD31. Spearman correlation test and t test were used for statistical analysis. RESULTS: Serum anti-p53 antibodies were positive in 25 (60%) of 41 tumor p53-positive patients. While the mean (SD, range) microvessel density was found to be 43 (7.59, 8-99) in patients who had positive serum anti-p53 antibodies, it was found to be 23 (4.53, 6-98) in patients who had negative serum anti-p53 antibodies. There was a good correlation between serum anti-p53 antibodies and microvessel density (p<0.05). No correlation was found between tumor p53 expression and microvessel density (p>0.05). CONCLUSIONS: We found that there is a significant correlation between the microvessel density and serum anti-p53 antibodies. This result may show the role of angiogenesis in the etiology of serum anti-p53 antibodies in bladder cancer patients.

Adult↗

PubMed2005

Oxidative stress promotes endothelial cell apoptosis and loss of microvessels in the spontaneously hypertensive rats.

OBJECTIVE: Endothelial cell apoptosis caused by oxidative stress may lead to the loss of microvessels (rarefaction) in hypertension. We examine here the effects of antioxidants on cell apoptosis and rarefaction. METHODS AND RESULTS: The juvenile spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were treated with superoxide scavengers, Tempol or Tiron, during growth. After the treatment, oxidative stress status, endothelial cell apoptosis rate, and microvessel length density in skeletal muscle and mesentery were evaluated in comparison with age-matched controls. Untreated 16-week-old SHR had higher oxidative stress (P<0.01) and cell apoptosis rate (P<0.05) and lower microvessel length density (371+/-17 mm/mm3 [P<0.01]) compared with age-matched WKY rats (435+/-15 mm/mm3). In the SHR, but not in WKY rats, systemically applied antioxidants attenuated oxidative stress and cell apoptosis rate (P<0.05 versus untreated controls) and prevented the loss of microvessels (411+/-15 mm/mm3 for Tempol [P<0.01 versus untreated control] and 399+/-17 mm/mm3 for Tiron [P<0.05]). CONCLUSIONS: Antioxidant treatment with cell-permeable superoxide scavengers inhibits endothelial cell apoptosis and prevents microvessel rarefaction in the SHR during growth.

Animals↗

PubMed1990

Microvessel changes in hypertension measured by Griffonia simplicifolia I lectin.

Commonly used methods for assessing reductions in microvascular density (rarefaction) in hypertension detect only perfused microvessels. In the present study, samples of cremaster and spinotrapezius muscles were taken from rats with chronic (4-week) reduced renal mass hypertension and normotensive sham-operated control rats, as well as from 12-week-old spontaneously hypertensive rats and their normotensive Wistar-Kyoto control strain. Mean arterial pressure was 149 +/- 8 mm Hg in the rats with reduced renal mass hypertension, 114 +/- 7 mm Hg in sham-operated rats, 177 +/- 9 mm Hg in spontaneously hypertensive rats, and 95 +/- 4 mm Hg in Wistar-Kyoto rats. Muscle samples were incubated with rhodamine-labeled Griffonia simplicifolia I lectin, which identifies both perfused and nonperfused microvessels. Microvascular density was assessed by counting intersections with a 20-microns grid. Microvessel density was significantly reduced in cremaster muscles of both spontaneously hypertensive and reduced renal mass hypertensive rats, and in the spinotrapezius muscle of spontaneously hypertensive rats, compared with their respective normotensive controls. Further studies in the reduced renal mass rats on low salt diets indicated that lectin binding was also decreased as salt intake was increased, independent of blood pressure. This change was not due to an alteration in lectin-binding affinity. These studies indicate that lectin binding can be a useful tool for assessing microvessel density that does not depend on the perfusion state of the vessels and that rarefaction due to hypertension is not evenly distributed in all vascular beds. These results also provide evidence that dietary salt intake alone can influence microvessel density, as measured by the lectin technique.

Animals↗

PubMed1996

Rapid microvessel rarefaction with elevated salt intake and reduced renal mass hypertension in rats.

To identify the sequence of events associated with the development of reduced vessel density (rarefaction) in hypertension, microvessel density and ultrastructure were assessed in the cremaster muscle of rats subjected to a 75% surgical reduction of renal mass and normotensive sham-operated control rats. Rats with reduced renal mass (RRM rats) and sham-operated rats were then maintained on either a high salt (4.0% NaCl) or a low salt (0.4% NaCl) diet for 3 days. Acute exposure to the high salt diet significantly increased mean arterial pressure in RRM rats but did not affect sham-operated control rats. Quantitative fluorescence microscopy of cremaster muscle whole mounts using rhodamine-labeled Griffonia simplicifolia I lectin revealed substantial rarefaction of microvessels in both RRM hypertensive rats and normotensive sham-operated rats on a high salt diet relative to corresponding control rats on a low salt diet. Confocal microscopy revealed a heterogeneous distribution of microvessels in RRM rats on a high salt diet, with some areas largely devoid of vessels. RRM and sham-operated rats on a high salt diet both exhibited changes in arteriolar ultrastructure, which included a loss of basement membranes and a dissociation of the endothelial and smooth muscle components of the vascular wall, resulting in a loss of vessel integrity. These observations demonstrate that a rapid loss of microvessels can occur not only in rats with RRM hypertension but also in normotensive rats on a high salt diet. This loss of microvessels results from structural alterations, which differ from the degenerative processes associated with microvascular rarefaction in rats with chronic RRM hypertension.

Animals↗

PubMed2005

Mechanism of myocardial microvessel formation in cyanotic congenital heart disease.

BACKGROUND: Patients with cyanotic congenital heart disease (C-CHD) usually have myocardial thickening and fibrosis, both of which can affect the course of surgical management. Hypoxia and ischemia may stimulate microvessel formation in the myocardium, which may accelerate the myocardial thickening and fibrosis. Whether hyperplasia of microvessels occurs in the myocardium of C-CHD was investigated in this report. METHODS AND RESULTS: The patients were divided into 2 groups; the C-CHD group (n = 22), and the acyanotic congenital heart disease (A-CHD) group (n = 24). The microvessels and vascular endothelial growth factor (VEGF) mRNA of the myocardium were detected by immunohistochemical staining assay and real-time quantitative reverse transcriptase polymeric chain reaction, respectively. The serum VEGF levels were measured by using enzyme-linked immunosorbent assay. The results were that: (1) the number of microvessels in the myocardium were more in the C-CHD group than in A-CHD group; (2) the serum VEGF levels in the C-CHD group vs the A-CHD group were higher in the preoperative period (p < 0.001), but there was no difference after operation; and (3) VEGF protein and the expression of VEGF mRNA in the myocardium were higher in the C-CHD group than in the A-CHD group (p < 0.01). CONCLUSIONS: Myocardial microvessels formed in the myocardium of patients with C-CHD, possibly mediated by increasing VEGF levels (for this group of patients).

Adolescent↗

PubMed2006

Microvessel density in the placental bed among preeclampsia patients.

CONTEXT AND OBJECTIVE: Morphological changes in the spiral arteries of the placental bed have been studied in patients with preeclampsia, one of the largest causes of maternal and perinatal morbidity and mortality. The reports show that vasospasm and vascular endothelial injury were two major pathological conditions for preeclampsia. The aim of this study was to investigate the microvessel density of spiral arteries in the placental bed, in pregnancies complicated by hypertension and proteinuria, and in normal pregnancies. DESIGN AND SETTING: This was a cross-sectional survey of immunohistochemical studies on biopsies from the spiral arteries of the placental bed, among women undergoing cesarean sections for clinical and obstetrical reasons at Universidade Federal de São Paulo, São Paulo, Brazil. METHODS: Placental bed biopsies were obtained during cesarean section after placenta removal, with direct viewing of the central area of placenta insertion. The microvessel density of spiral arteries was measured by immunohistochemical methods in decidual and myometrial segments, using CD34 antibody. RESULTS: Biopsies containing spiral arteries were obtained from 34 hypertensive pregnant women with proteinuria, and 26 normotensive pregnant women. The microvessel densities in decidual and myometrial segments of the placental bed were compared between the groups. It was observed that, with increasing blood pressure and proteinuria, the microvessel density gradually decreased. CONCLUSION: The presence of high levels of hypertension and proteinuria may be associated with a progressive decrease in microvessel density in the placental bed.

Adult↗

PubMed1994

Hypoxia increases superoxide anion production from bovine coronary microvessels, but not cardiac myocytes, via increased xanthine oxidase.

OBJECTIVE: To determine if 30 min of hypoxia (PO2 8-10 Torr) affects basal, mitochondrial, or xanthine oxidase-derived lucigenin-detectable superoxide anion (O2.-) production by intact isolated bovine coronary microvessels and myocytes. METHODS: O2.- was quantitated by lucigenin-elicited chemiluminescence. Antimycin A (10 microM) and hypoxanthine (0.1 mM) were employed to increase O2.- from mitochondria and xanthine oxidase, respectively. RESULTS: Chemiluminescence from microvessels and myocytes was enhanced (approximately twofold, P < 0.05, n = 8-10) by inhibition of Cu,Zn-SOD via pretreatment with diethyldithiocarbamate (10 mM, 30 min) and was decreased (P < 0.05, n = 8-10) by an intracellular scavenger of O2.- (10 mM Tiron), but not by added SOD (3 microM, n = 8-10). In the presence of SOD inhibition, hypoxia produced a hypoxanthine-dependent (n = 8-10) twofold increase in chemiluminescence (P < 0.05, n = 10) in microvessels but not in myocytes. Other combinations of hypoxia, antimycin, or hypoxanthine did not significantly alter chemiluminescence. CONCLUSIONS: Lucigenin appears to detect a basal intracellular source of O2.- in both microvessels and myocytes that is not derived from mitochondria or xanthine oxidase. Exposure to hypoxia does not appreciably increase basal O2.- in vessels or myocytes, but if exogenous hypoxanthine is supplied, microvessels show an increase in O2.- production presumably derived from xanthine oxidase.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗

PubMed1995

Type II collagen is a major component of bovine retinal microvessel extracellular matrix.

OBJECTIVE: To determine which interstitial collagen types may be present in bovine retinal microvessel extracellular matrix (ECM). METHODS: Dissociated bovine microvessels were treated with detergents and the resultant purified ECM monitored by transmission electron microscopy (TEM). Pepsin-extracted soluble ECM collagens were identified by Western blots. Collagens were further purified by neutral salt precipitation and carboxymethyl cellulose (CMC) chromatography before cyanogen bromide (CNBr) peptide mapping and two-dimensional peptide mapping of CMC-generated fractions. Interstitial collagens were localized by immunofluorescence on frozen sections. RESULTS: Transmission electron microscopy of detergent-purified microvessel ECM demonstrated numerous 10-50-nm collagen fibrils associated with basal laminae regardless of vessel diameter. Western blots showed that soluble ECM collagens were strongly positive for type II, moderate for type III, and weak for type I. CNBr peptide maps and two-dimensional maps of neutral salt and CMC-purified fractions confirmed the presence of type II collagen. Immunofluorescence localized type II collagen in large and small vessels of the retina. CONCLUSIONS: Type II collagen is an unexpected major component of bovine microvessel ECM, whereas types I and III are present in minor amounts. Type V collagen is also a substantial ECM component. Accordingly, all four types may contribute to a heterogeneous population of collagenous fibrils identified by TEM in intact isolated retinal microvessel ECM.

Animals↗

PubMed1997

Imaging of oxygen saturation and distribution of erythrocytes in microvessels.

OBJECTIVE: To construct images of oxygen saturation and the distribution of erythrocytes in a network of microvessels. METHODS: The image of a small group of microvessels under an inverted microscope was incorporated into an image processor through a video camera and was digitized. Based on the information obtained through six visible interference filters of different wavelengths, oxygen saturation and the amount of erythrocytes in microvessels were calculated with a computer. The system was applied to a microvascular bed of isolated rabbit mesentery perfused with a suspension of human erythrocytes. RESULTS: In a steady flow, with lowering of tissue oxygen tension by superfusion with nitrogen-bubbled isotonic saline containing 20 mmol/L sodium dithionite, the decrease of oxygen saturation of erythrocytes from arterioles to venules was imaged. Simultaneously, the distribution of erythrocytes in the microvessels was imaged and the marginal cell-free layer was profiled under high magnification. No significant alteration of the erythrocyte distribution on the deoxygenation of erythrocytes was observed. The exposure of erythrocytes to acidic pH and the decrease of the flow velocity of erythrocytes increased the release of oxygen from the erythrocytes in microvessels. CONCLUSIONS: The present method will be useful for the comprehensive analysis of oxygen transfer in the microvascular network, on the basis of both changes of the oxygen saturation and the flow behavior of erythrocytes.

Animals↗

PubMed2004

Sonographic depiction of microvessel perfusion: principles and potential.

OBJECTIVE: To provide an overview of the technical aspects and potential clinical applications of microvessel perfusion as depicted by microbubble-enhanced sonography. METHODS: Sonographic depiction of microvessel perfusion was obtained by microbubble-enhanced sonography. This technique was used for imaging in vivo murine tumors and was correlated with magnetic resonance and fluorodeoxyglucose autoradiography. Sonographic estimation of microvessel perfusion used parameters derived from time-activity curves. RESULTS: Preliminary data indicate that accurate and reproducible quantification of microvessel perfusion is possible with the use of microbubble-enhanced sonography. CONCLUSIONS: Microbubble-enhanced sonography can depict microvessel perfusion. This technique has several potential clinical applications, including assessment of tumor blood flow and changes that occur with treatment.

Animals↗

PubMed1998

[The effect of ectopic HCG on microvessel density in gastric carcinoma].

OBJECTIVES: To study the effect of ectopic HCG on microvessel density in gastric carcinoma using immunohistochemical staining with anti-beta-HCG polyclonal antibody and anti-factor VIII related antigen(FVIII RAg)antibody. METHODS: A total of 40 specimens resected from patients with gastric carcinoma was investigated by immunohistochemical staining with a anti-beta-HCG polyclonal antibody and a monoclonal antibody against FVIII RAg. The expression of beta-HCG and the microvessel density(the average number of microvessel in three areas of highest vascular density at 400 x magnification) in various regions of the histologic specimens were studied. RESULTS: Fifteen (37.5%) of the 40 gastric carcinomas was positive for beta-HCG protein in tumor tissue. beta-HCG protein was negative in the tumor-adjacent and in normal tissue. The mean microvessel density was 27.4 +/- 7.1 in the tumor, 11.9 +/- 5.4 in tumor-adjacent and 4.8 +/- 1.5 in normal tissues (P < 0.05-0.01). There was a close correlation with beta-HCG positivity and microvessel density (MVD). There was no correlation between the degree of tumor cell differentiation and beta-HCG expression, nor was a correlation between it and MVD. High expression level of beta-HCG and MVD was significantly associated with hematogenous metastases. CONCLUSION: Ectopic HCG expression may have angiogenic effect which, in turn, may facilitate hematogenous dissemination of gastric cancer.

Adenocarcinoma↗

PubMed2001

Image analysis of microvessel surface area predicts radiosensitivity in early-stage laryngeal carcinoma treated with radiotherapy.

PURPOSE: The tissue oxygenation level, which is theoretically governed by distance from blood vessels, is one of the most important modulators of the radiosensitivity of carcinoma. A computed image analysis system for the detection of tissue oxygenation was developed to establish a method of predicting radiosensitivity in early-stage laryngeal carcinoma treated by curative radiotherapy. EXPERIMENTAL DESIGN: Microvessel structures labeled with CD31 antigen were investigated in 55 patients undergoing curative radiotherapy for T1 and T2 laryngeal carcinoma. We calculated (a) microvessel density [(MVD) vessels/field] under a microscope; (b) the ratio of the total microvessel number (TN):tumor area (TA) [TN:TA; vessels/mm2]; (c) the ratio of the total microvessel perimeter (TP):TA (TP:TA; mm/mm2); and (d) the ratio of tumor tissue area >150 microm from microvessels (hypoxic ratio; %) as parameters of tissue oxygenation in each whole biopsy specimen by using an image analyzer. We compared each of these factors with radiosensitivity. RESULTS: Mann-Whitney's U test revealed that tumors with a high MVD (median, 42 vessels/field), high TN:TA ratio (median=40.9 vessels/mm2), high TP:TA ratio (median, 2.92 mm/mm2), and low hypoxic ratio (median, 30.3%) had significantly greater radiosensitivity than tumors with a low MVD, low TN:TA ratio, low TP:TA ratio or high hypoxic ratio (P = 0.002, P = 0.0004, P < 0.0001, and P = 0.004, respectively). CONCLUSIONS: Prediction of radiosensitivity on the basis of the TP:TA ratio can be used as an efficient means of avoiding ineffective radiation, complications after salvage surgery, and prolonged hospital stays.

Adult↗

PubMed2002

[Observation of the microstructure and ultrastructure of microvessels induced by OS-732 cell line].

OBJECTIVE: To observe the characteristics of the microstructure and ultrastructure of the microvessels induced by human osteosarcoma cell line (OS-732). METHODS: OS-732 cells were inoculated into the chick embryo chorioallantoic membrane to induce the growth of microvessels, the microstructure and ultrastructure of which were observed using dissecting microscope, light microscope and transmission electron microscope. RESULTS: OS-732 cell line was strongly angiogenic, and newly generated capillaries converging upon the tumor were visualized under dissecting microscope. Observation with transmission electron microscope found that the wall of the microvessels deficient in elements of smooth muscles was consisted of a monolayer of vascular endothelial cells with widened gaps in between, and the basement membrane appeared irregular. CONCLUSION: The microvessels induced by tumors have pathological and physiopathological characteristics consistent with the tumors, and setting the microvessels as a therapeutic target against osteosarcoma may help improve the prognosis of patients with this disease.

Animals↗

PubMed2004

In vivo imaging of the rat cerebral microvessels with optical coherence tomography.

A technique called optical coherence tomography (OCT) was applied to in vivo observation of microcirculation in the rat cerebral cortex. The OCT system used in this study provided cross-sectional images of the cerebral cortical tissue up to about 1 mm depth with longitudinal resolution up to 8 microm. It could visualize cross-sectional structure of the dura, arachnoid membrane, cortical tissue, and pial microvessels through the cranial window. Pial microvessels with diameter larger than several 10 microm could be detected to observe their cross-sectional shape, while the microvessels within the cortical tissue with smaller diameter were not discernible. The OCT observation revealed that the pial microvessels showed different spatial configurations depending on the cerebral preparations with intact dura and without dura. Stimulus responses of the somatosensory cortices were also different among the preparation methods; Delayed swelling of the cortical surface appeared in the somatosensory cortex following the electrical stimulation of the hind paw in the case of dura removal, which was restricted to a thin surface layer with less than several 10 microm. It is considered to reflect the reactive hyperemia accompanying the neuronal activation. Doppler frequency shift due to the blood flow was detected in pial arterioles. This phenomenon is promising to provide the velocity profile within microvessels and may be applicable to the functional imaging of the brain.

Animals↗

PubMed1991

Measurement of gene expression in human retinal microvessels by solution hybridization.

Changes in gene expression could play a central role in the phenotypic abnormalities of the retinal vascular cells observed in diabetic retinopathy and other retinal diseases. To measure gene expression in human retinal microvessels, a RNA-probe excess solution hybridization assay was used. Retinal microvessels were isolated from eyes obtained within 36 hr of death, and intact RNA was extracted by the guanidine method. Hybridization of poly(A)+ RNA northern blots revealed only the cytoskeletal beta-actin message; by using the more sensitive solution hybridization assay, the plasminogen activator-inhibitor 1 (PAI-1) and von Willebrand factor (vWF) mRNAs were quantified. The prevalence of these transcripts in the retinal microvessels was 0.04 x 10(6) copies/ng RNA for PAI-1 and 0.14 x 10(6) copies/ng RNA for vWF, much less than the prevalence in human umbilical vein endothelial cells (1.93 x 10(6) and 3.90 x 10(6), respectively). The PAI-1 mRNA levels in retinal microvessels isolated from five type II diabetic patients were significantly higher than those in vessels isolated from ten age-matched controls (0.06 x 10(6) versus 0.04 x 10(6) copies/ng RNA, P less than 0.05). The solution hybridization assay accurately measured low-abundance mRNAs in human retinal microvessels; determination of gene expression in these cells could aid in understanding the pathogenesis of important ophthalmologic diseases such as diabetic retinopathy.

Actins↗