UT-B1 urea transporter is expressed along the urinary and gastrointestinal tracts of the mouse.

Selective transporters account for rapid urea transport across plasma membranes of several cell types. UT-B1 urea transporter is widely distributed in rat and human tissues. Because mice exhibit high urea turnover and are the preferred species for gene engineering, we have delineated UT-B1 tissue expression in murine tissues. A cDNA was cloned from BALB/c mouse kidney, encoding a polypeptide that differed from C57BL/6 mouse UT-B1 by one residue (Val-8-Ala). UT-B1 mRNA was detected by RT-PCR in brain, kidney, bladder, testis, lung, spleen, and digestive tract (liver, stomach, jejunum, colon). Northern blotting revealed seven UT-B1 transcripts in mouse tissues. Immunoblots identified a nonglycosylated UT-B1 protein of 29 kDa in most tissues and of 36 and 32 kDa in testis and liver, respectively. UT-B1 protein of gastrointestinal tract did not undergo N-glycosylation. Immunohistochemistry and in situ hybridization localized UT-B1 in urinary tract urothelium (papillary surface, ureter, bladder, and urethra), prominently on plasma membranes and restricted to the basolateral area in umbrella cells. UT-B1 was found in endothelial cells of descending vasa recta in kidney medulla and in astrocyte processes in brain. Dehydration induced by water deprivation for 2 days caused a tissue-specific decrease in UT-B1 abundance in the urinary bladder and the ureter.

Spatiotemporal distribution of insulin-like growth factor receptors during nephrogenesis in fetuses from normal and diabetic rats.

Exposure to hyperglycemia in utero impairs rat nephrogenesis. The effect of maternal diabetes on insulin-like growth factors and their receptors in the fetal kidney is associated with an increase in both mRNA and protein of the insulin-like growth factor II/mannose 6-phosphate receptor. However, this receptor has never been localized in the fetal kidney. The spatial and temporal distribution of the three insulin-like growth factor receptors (insulin-like growth factor I receptor, insulin-like growth factor II/mannose 6-phosphate receptor and insulin receptor) in rat metanephros during both normal and streptozotocin-induced diabetic renal development was investigated using in situ hybridization and immunohistochemistry. All receptors were found in the fetal kidney from the start of nephrogenesis. Insulin-like growth factor I receptor expression was ubiquitous and continuously present during metanephric development. Insulin receptor expression was developmentally regulated during kidney maturation with an enhanced expression in proximal tubules at the late stages of development. Insulin-like growth factor II/mannose 6-phosphate receptor expression was ubiquitous in the early stages of development and was dramatically decreased at the late stages of normal kidney development. Insulin receptor and insulin-like growth factor I receptor expressions were unchanged in diabetic metanephroi. Although the spatial expression of insulin-like growth factor II/mannose 6-phosphate receptor was unaffected by hyperglycemia, its expression was not downregulated in the mesenchyme of the nephrogenic zone of diabetic fetuses on gestational day 20. This study suggests a crucial role of insulin-like growth factor II/mannose 6-phosphate receptor in the pathogenesis of the impaired nephrogenesis in fetuses of diabetic mothers.

Genetically increased angiotensin I-converting enzyme level and renal complications in the diabetic mouse.

Diabetic nephropathy is a major risk factor for end-stage renal disease and cardiovascular diseases and has a marked genetic component. A common variant (D allele) of the angiotensin I-converting enzyme (ACE) gene, determining higher enzyme levels, has been associated with diabetic nephropathy. To address causality underlying this association, we induced diabetes in mice having one, two, or three copies of the gene, normal blood pressure, and an enzyme level range (65-162% of wild type) comparable to that seen in humans. Twelve weeks later, the three-copy diabetic mice had increased blood pressures and overt proteinuria. Proteinuria was correlated to plasma ACE level in the three-copy diabetic mice. Thus, a modest genetic increase in ACE levels is sufficient to cause nephropathy in diabetic mice.

Normal IgG protects against acute graft-versus-host disease by targeting CD4(+)CD134(+) donor alloreactive T cells.

Intravenous immunoglobulin (IVIg) was shown to decrease the severity of acute graft-versus-host disease (aGVHD) in recipients of allogeneic bone marrow transplants. To investigate the mechanisms involved in the protective effect of IVIg, we have used the parent-into-F1 model in which parental lymphocytes are transferred into semi-syngeneic non-irradiated F1 rats. Here we report that IVIg, as well as F(ab')(2) fragments of IVIg, protected (Lewis x Brown-Norway) F1 rats against aGVHD induced by a single injection of Lewis lymphocytes. IVIg was given as five consecutive daily injections, starting on the day preceding that of the transfer of Lewis cells. Protection was associated with a decreased ability of lymphocytes to spontaneously proliferate and to produce NO and IFN-gamma, in the absence of an increased production of IL-10. We further demonstrate that protection was associated with a decrease in CD4(+) T cells bearing the activation marker CD134 in vivo, and with an enhanced apoptosis of activated CD4(+) T cells by IVIg, in vitro. Our observations suggest that the prevention of aGVHD by IVIg in this model is mediated by the induction of apoptosis of activated alloreactive CD4(+)CD134(+) donor T cells. The results further emphasize the role of normal immunoglobulin in modulating alloantigen immune responsiveness.

Inflammation is probably not a prerequisite for renal interstitial fibrosis in normoglycemic obese rats.

We examined the role of inflammation in the development of renal interstitial fibrosis in Zucker obese rats, which rapidly present kidney lesions in the absence of hypertension and hyperglycemia. Type I and III collagens were quantified using a polarized light and computer-assisted image analyzer. The expression of mRNA encoding matrix components, adhesion molecules, chemokines, and growth factors was followed by RT-PCR. The presence of synthesized proteins as well as lymphocytes and macrophages was determined by immunohistochemistry. Interstitial fibrosis developed in two phases. The first phase occurred as early as 3 mo and resulted from a neosynthesis of type III collagen and fibronectin and a reduction of extracellular matrix catabolism, in parallel with an overexpression of transforming growth factor-beta(1) and in the absence of any lymphocyte or macrophage infiltration. After 6 mo, interstitial fibrosis worsened with a large accumulation of type I collagen, concomitantly with a large macrophage infiltration. Thus inflammation cannot explain the onset of interstitial fibrosis that developed in young, insulinoresistant, normoglycemic, obese Zucker rats but aggravated this process afterward.

Early glomerular macrophage recruitment in streptozotocin-induced diabetic rats.

Diabetic glomerulosclerosis is defined by increased glomerular extracellular matrix (ECM) that is mainly synthesized by mesangial cells that underwent an activation mediated by cytokines and growth factors from various cellular origins. In this study, we tested whether macrophages could infiltrate the glomeruli and influence ECM synthesis in experimental diabetes. To test our hypothesis, we initially studied the dynamics of glomerular macrophage recruitment in streptozotocin-induced diabetic rats at days 1, 2, 4, 8, 15, and 30 by using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) on isolated glomeruli and immunohistochemistry and morphometry. We then assessed the role of macrophages on the basis of the pharmacological modulation of their recruitment by insulin or ACE inhibitor treatments and by X-irradiation-induced macrophage depletion at days 8 and 30. Macrophages were recruited within the glomeruli at the very early phase of hyperglycemia by using RT-PCR CD14 detection from day 2 and by using ED1 immunohistochemistry from day 8. This glomerular macrophage infiltration was associated with an increase in alpha1-chain type IV collagen mRNA. In parallel, the diabetic glomeruli became hypertrophic with an increase in the mesangial area. Macrophage recruitment was preceded by or associated with an increased glomerular expression of vascular cell adhesion molecule 1, intracellular adhesion molecule 1, and monocyte chemoattractant protein 1, which contributes to monocyte diapedesis. Glomerular interleukin-1beta mRNA synthesis was also enhanced as early as day 1 and could be involved in the increase in ECM and adhesion molecule gene expressions. Insulin treatment and irradiation-induced macrophage depletion completely prevented the glomerular macrophage recruitment and decreased alpha1-chain type IV collagen mRNA and mesangial area in diabetic rats, whereas ACE inhibitor treatment had an incomplete effect. It can be concluded that in the streptozotocin model, hyperglycemia is followed by an early macrophage recruitment that contributes to the molecular and structural events that could lead to glomerulosclerosis. Therefore, besides direct stimulation of mesangial cells by hyperglycemia, macrophages recruited in the glomeruli during the early phase of hyperglycemia could secondarily act on mesangial cells.

The endothelin system in human and monkey ovaries: in situ gene expression of the different components.

The endothelin system is composed of three endothelin isoforms (ET-1, ET-2, and ET-3), the endothelin receptors ETA and ETB, and the endothelin-converting enzyme (ECE). Besides having a major vasoactive role, endothelins have roles in different cell types at a local level. We investigated the presence of the different components of the endothelin system in primate ovaries. Human ovaries and gonadotropin-stimulated monkey ovaries were studied using immunohistochemistry for endothelin, and in situ hybridization with probes for ET-1, ET-2, ET-3, ETA and ETB receptors, and ECE. ET-1 and ETA receptors were detected in endothelial cells and vascular smooth muscle cells, respectively, in stromal vessels adjacent to follicles and corpora lutea. ETB receptors and ET-1 were found in the endothelial cells of capillaries of corpora lutea. ECE was present in internal theca cells of secondary, de Graaf, atretic follicles, and in luteinized granulosa cells of the corpora lutea. The endothelin system components are present in or around the follicles of human and monkey ovaries. Although the components are not expressed in the same cell types, they are synthesized, mainly in follicles, by cells that are in close proximity. Thus, the endothelin system could act in a paracrine manner. ECE expression in steroid-producing cells changes its compartmentalization during follicle maturation.

Immunolocalization of the Na+/H+ exchanger isoform NHE2 in rat kidney.

Four Na+/H+ exchangers (NHE1 to NHE4) have been detected in the kidney. Renal NHE2 expression sites have not been fully established. We have raised rabbit antisera against an oligopeptide related to the amino acids 652 to 661 of rat NHE2. Western blot analysis of plasma membrane fractions isolated from rat renal cortex showed that affinity-purified anti-NHE2 antibody detected an 85-kDa protein in apical but not in basolateral membranes. The labeling of this 85-kDa protein was specifically blocked by preincubation of the antibody with its monomeric peptide, indicating specific recognition. Indirect immunolabeling was performed on sections of paraformaldehyde-fixed rat kidney embedded in paraffin. Strong staining was seen in the apical membrane of cortical thick ascending limbs, distal convoluted tubules, and connecting tubules. Much weaker apical staining was found in medullary thick ascending limbs of Henle. In the inner medulla, some thin limbs were intensively labeled by the anti-NHE2 antibody. No staining could be detected in any segments of the proximal tubule and collecting duct.

[Lactic acidosis and hepatic mitochondrial changes during a treatment with zidovudine]. / Acidose lactique et altérations mitochondriales hépatiques au cours d'un traitement par zidovudine.

Adverse effects of zidovudine, which mainly result in myopathies and hematological disorders, could be due to multitissular mitochondrial toxicity of the drug. During zidovudine treatment, most cases of lactic acidosis have been attributed to mitochondrial myopathy. We report a case of hepatocellular failure with lactic acidosis in a 33 year-old patient with the human immunodeficiency virus infection and treated with zidovudine for 8 months. Liver biopsy showed massive macrovacuolar steatosis and ultrastructural mitochondrial abnormalities similar to those previously described in the skeletal muscle. This is the second reported case of lactic acidosis and hepatocellular failure which is probably related to hepatic mitochondrial dysfunction caused by zidovudine.

Morphometric detection of incipient glomerular lesions in diabetic nephropathy in rats. Protective effects of ACE inhibition.

BACKGROUND: Glomerulosclerosis is the main renal lesion complicating diabetes in humans and in experimental models. Angiotensin I-converting enzyme (ACE) inhibitors are effective in preventing the development of diabetic nephropathy. Incipient glomerular lesions were explored in streptozotocin-diabetic rats at a stage when glomerulosclerosis was not yet established. The modulation of such early glomerular lesions by a new ACE inhibitor (Trandolapril (T) at high or low doses was assessed. EXPERIMENTAL DESIGN: Five groups of rats were designed as follows: (a) nondiabetic control rats, (b) diabetic rats, (c) diabetic rats treated with 0.1 mg/kg/day of T, (d) diabetic rats treated with 1 mg/kg/day of T, and (e) nondiabetic rats treated with 1 mg/kg/day of T. The rats were killed at 1, 3, and 6 months after the beginning of the treatment. The kidneys were studied using a powerful morphometric technique at optical microscopic level with an image analyzer to measure the following glomerular parameters to assess the development of incipient glomerular lesions: (a) total glomerular surface area, (b) glomerular tuft surface area, (c) mesangial surface area, (d) ratio of the mesangial surface area to the glomerular tuft surface area, and (e) mean thickness of the Bowman's capsule. In parallel, albuminuria was measured. RESULTS: The results showed the development of glomerular hypertrophy in parallel with the increase in glomerular mesangial domain and in albuminuria with diabetes. They also demonstrated that ACE inhibitor given at a high dose is significantly effective in reducing glomerular hypertrophy and the expansion of the mesangial domain. ACE inhibitor given at a low dose tended to reduce glomerular hypertrophy and the expansion of the mesangial domain. Furthermore, ACE inhibitor at both doses completely abolished the albuminuria increase, maintaining the levels of albuminuria within the range of young nondiabetic rats. CONCLUSIONS: Using morphometric image analysis, incipient glomerular changes can be detected before glomerulosclerosis is patent in experimental diabetes. Moreover, they can be easily and reliably quantified by this technique, allowing comparison among experimental groups. These changes can be prevented by ACE inhibition.

Hyponatremic hypertensive syndrome and massive proteinuria in a patient with renin-producing leiomyosarcoma.

We report a case of renin-producing leiomyosarcoma associated with the hyponatremic hypertensive syndrome and nephrotic-range proteinuria. Extremely high levels of active renin and, to a greater extent, of prorenin were found in plasma and tumor tissue. Immunohistochemical and in situ hybridization studies demonstrated that the neoplastic cells were the source of renin production. The hyponatremic hypertensive syndrome and proteinuria promptly responded to treatment with angiotensin-converting enzyme inhibitors, suggesting an angiotensin II dependency of these disorders. After removal of the leiomyosarcoma, plasma concentration of active renin, but not of prorenin, normalized and the hypertension, proteinuria, and electrolyte abnormalities disappeared. However, 5 months after operation, the patient presented once again with hypertension, hypokalemia, proteinuria, and markedly increased plasma levels of both active renin and prorenin that heralded the relapse of neoplastic disease.

Erythropoietin synthesis by tumor cells in a case of meningioma associated with erythrocytosis.

While secondary erythrocytosis is often associated with tumors arising from the kidney, other tumors have been described to originate in the liver, uterus, ovary, adrenal gland, and central nervous system, among which cerebellar hemangioblastomas are involved in most instances. Two cases of meningioma associated with erythrocytosis have already been reported. We observed a 59-year-old female patient who had developed a frontal meningioma associated with erythrocytosis. Before surgery, she had a significantly elevated total red blood cell volume with a normal plasma volume. Serum erythropoietin (Epo) dosage assessed by radioimmunoassay was within the normal range. The tumor was removed and the pathologic study found a meningotheliomatous meningioma. Total RNA from the tumor was hybridized to a monkey cDNA Epo probe. A strong 1.6-kb messenger RNA (mRNA) signal was observed, which is the expected size of human Epo mRNA. In situ hybridization with the 35S-labeled Epo probe was performed on frozen tumor tissue sections. A significant hybridization was observed in all the tumor cells, whereas the stroma was negative. Therefore, in this meningioma associated with erythrocytosis, Epo was produced by the tumor cells themselves.

Poor diagnostic value of in situ hybridization and immunohistochemistry in endomyocardial biopsies to detect cytomegalovirus after heart transplantation.

Cytomegalovirus (CMV) infection is a major cause of morbidity and death in heart transplant recipients. Cardiac graft involvement in CMV infection is a matter of controversy, considering its frequency and its relationship with acute or chronic rejection. Four heart transplant patients were selected because of a severe CMV infection (systemic, gastrointestinal, ophthalmic, and neurologic involvement). Immunoglobulin M and increased immunoglobulin G CMV antibodies developed. Twenty-two routine endomyocardial biopsies (EMB; mean: 5.5 EMB per patient; range, 3 to 9) from these patients were selected covering the period of CMV infection. Grading of rejection showed 12 biopsies with "no evidence of rejection (grade 0)," nine biopsies with "mild acute rejection (grade 1B)," and one biopsy with "moderate acute rejection (grade 3A)." One EMB exhibited a single CMV inclusion in an endothelial cell detectable by light microscopy. The EMB were assessed for CMV infection using in situ hybridization (ISH) for the detection of CMV genome with a biotinylated CMV probe and immunohistochemistry (IHC) for the detection of CMV immediate-early antigen with the monoclonal antibody E13. ISH and IHC detected a single CMV-infected cell, respectively, in one and two EMB from two patients. The patient with a CMV inclusion determined by light microscopy was also positive with both techniques. Positive ISH and IHC were always in enlarged inclusion-bearing cells, which were easily observable with routine staining. One EMB had mild acute rejection, and the other one had no rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Successful detection by in situ cDNA hybridization of three members of the serpin family: angiotensinogen, alpha 1 protease inhibitor, and antithrombin III in human hepatocytes.

In situ hybridization was used to investigate the presence of mRNAs of three members of the serine protease inhibitor (serpin) superfamily, angiotensinogen (AG), alpha 1 protease inhibitor (alpha 1PI), and antithrombin III (ATIII) in normal human liver. The probes were full length 35S radiolabeled complementary DNAs of human AG, alpha 1PI, and ATIII. The three mRNAs were found to be uniformly distributed in all hepatocytes, with no evidence of any special distribution, but the signal was more intense for alpha 1PI than for AG and ATIII. Kupffer cells, biliary epithelial cells, and vascular cells were all negative. The same tissue was studied by peroxidase-antiperoxidase immunohistochemistry using specific antibodies against AG, alpha 1PI, and ATIII. No significant amounts of any of the proteins, alpha 1PI, AG, or ATIII were detected in frozen or fixed sections of normal liver. This study indicates that these proteins are not stored in the normal human hepatocyte, but that their genes are actively expressed and that in situ hybridization is the only technique presently available to detect their presence.

Detection and localization of renin messenger RNA in human pathologic tissues using in situ hybridization.

In order to investigate the synthesis of renin in human pathologic tissues, the authors used in situ hybridization to detect and localize renin messenger RNA (mRNA). The probe was a 35S-radiolabeled 1.1-kb length complementary DNA of human renal renin. To compare the synthesis with the presence and the storage of renin, renin antigen was assessed by immunohistochemistry in the same tissues. The human pathologic tissues were as follows: two ischemic kidneys related to renovascular hypertension; two renal juxtaglomerular cell tumors; one extrarenal renin-secreting epithelioid sarcoma of soft tissues. In ischemic kidneys, the cells containing both renin mRNA and renin protein were found in numerous juxtaglomerular apparatus and in the wall of arterioles, shown by combined in situ hybridization and immunohistochemistry. Most of the tumor cells in the juxtaglomerular cell tumors and scarce tumor cells in the epithelioid sarcoma of soft tissues were positive by in situ hybridization and immunohistochemistry. These findings demonstrate that the presence of renin in these tissues is associated with local cellular production of renin. In particular, smooth muscle cells of the wall of arterioles are definitely capable of synthesizing renin. Moreover, in these tissues, gene expression (renin synthesis) and renin storage are concordant.

Effect of HgCl2 on experimental allergic encephalomyelitis in Lewis rats. HgCl2-induced down-modulation of the disease.

HgCl2 induces autoimmunity in Brown-Norway rats and immunosuppression in Lewis rats. In the latter rats, HgCl2 triggers the proliferation of T suppressor/cytotoxic (OX8+) cells which actively suppress T cell functions. This led us to study the effect of HgCl2 on experimental allergic encephalomyelitis (EAE), a T cell-mediated autoimmune disease obtained following immunization with basic protein (BP). It will be shown that HgCl2 attenuates or even prevents clinical manifestations of EAE and inhibits both the proliferative response of T cells to BP and the anti-BP antibody response. This immunosuppression was not due to a defect at the T helper cell or antigen-processing cell level but to the emergence of T suppressor cells.

Effect of methylprednisolone and cyclophosphamide in mercury-induced autoimmune glomerulonephritis.

The effects of methylprednisolone and of cyclophosphamide were tested in mercury-induced autoimmune disease in Brown-Norway rats. Survival, proteinuria, presence of antiglomerular basement membrane bound antibodies and of immune complex type deposits, amounts of circulating immune complexes, and total serum IgE were studied. Serum IgE represents the most sensitive marker in this drug-induced autoimmune disease. Methylprednisolone alone (1.5 mg/kg per day) affected the course of the disease only slightly. Cyclophosphamide (20 mg/kg every other day) given from day 0 completely prevented all the autoimmune manifestations, but the rats were profoundly immunosuppressed. The same protective effect was obtained with lower cyclophosphamide dosage (15 mg/kg on day 0 and then 2 mg/kg per day). More interestingly, cyclophosphamide given from day 10 or 15 (20 mg/kg twice a week or every other day), at a time when the disease was already expressed, resulted in partial or complete recovery, provided that the rats had not exhibited heavy proteinuria before initiation of treatment. Cyclophosphamide is therefore a powerful agent, able to prevent and even to reduce the consequences of polyclonal activation in this model.

Phagocytosis of heat-aggregated immunoglobulins by mesangial cells: an immunoperoxidase and acid phosphatase study.

It has been demonstrated previously that mesangial cells (MC) phagocytose particulate material and nonimmune proteins, but that cells are able to engulf aggregated immunoglobulins (Igs) has not been proven so far. To investigate this cell function, heat-aggregated antiperoxidase (HRP) Igs were injected intravenously into Lewis rats. Sequential immunoelectron microscopic studies revealed that the injected material accumulates progressively in the extracellular compartment from 10 minutes to 5 hours and disappear afterward. This disappearance was related in part to the incorporation of aggregated anti-HRP Igs within phagosomes and phagolysosomes by MC. Quantitation of the phagocytic process showed that it starts as early as 10 minutes after injection and reaches its peak at 2.5 hours. Endocytosis seems to be associated with the sequestration of injected Igs within large cytoplasmic invaginations and with micropinocytosis. To further support these observations, ultrastructural cytochemistry for acid phosphatase activity was performed. Quantitative studies showed that the number of acid phosphatase-labeled lysosomes in MC was up to 7-fold greater in rats receiving aggregated anti-HRP Igs than in noninjected ones. In conclusion, our combined immunoperoxidase and acid phosphatase studies show that MC possess a vacuolar (lysosomal) apparatus capable of handling heat-aggregated Igs. Whether these cells are also operational in the disposal of soluble immune complexes in spontaneous and experimental conditions remains to be proven. In addition, observations suggesting the drainage of macromolecules from mesangium to the juxtaglomerular apparatus and from mesangium to the urinary space are presented.

Trapping of circulating proteins in immune deposits of Heymann nephritis.

The renal distribution of autologous and heterologous albumin and IgG was studied by electron microscopy using peroxidase-labeled conjugates in rats with Heymann nephritis. In addition, the renal distribution of autologous and heterologous antiperoxidase IgG and their F(ab')2 and Fab fragments was detected using peroxidase alone. All of these proteins crossed the glomerular lamina densa and passed into the urinary space by an extracellular pathway through the epithelial slits and the sites of epithelial detachment. The proteins were trapped in subepithelial immune deposits irrespective of the degree of proteinuria and regardless of the molecular weight, the autologous or heterologous origin, and the electric charges of the protein studied. The trapping was transient and easily reversed. These findings suggest that circulating proteins are able to modify the composition of immune deposits, thereby altering the course of immune complex disease.

Histochemical and ultrastructural characterization of subendothelial glycoprotein microfibrils interacting with platelets.

The interaction of human blood platelets with collagenase-treated rabbit subendothelium was studied by histochemical ultrastructural methods and by morphometric semi-quantitative analysis. Aortas were deendothelialized and incubated: 1) with a highly purified bacterial collagenase whose specificity was controlled; and 2) with the same collagenase followed by chymotrypsin. For histochemical studies, tannic acid, ruthenium red, and peroxidase-labeled Ricinus communis and concanavalin A were used. Electron microscopy showed that after digestion of fibrillar collagen by collagenase, adherent and aggregated platelets were observed on Ricinus communis-, concanavalin A-, and ruthenium red-positive glycoprotein microfibrils. After successive incubation with collagenase and chymotrypsin, the microfibrils disappeared. No platelets were observed on the remnant amorphous elastin. Morphometric analysis confirmed the interaction of platelets with collagenase-treated subendothelium. In addition, glycoproteins were extracted from collagenase-treated rabbit aortas using 5 M guanidine. Using an in vitro quantitative test, significant platelet adhesion to these glycoproteins was observed. Our results show an interaction between platelets and noncollagenic glycoprotein microfibrils.