d-alpha-tocopherol treatment prevents glomerular dysfunctions in diabetic rats through inhibition of protein kinase C-diacylglycerol pathway

Since diabetes now accounts for 35% of all new cases of end-stage renal disease in the United States, it is really important to prevent the onset of diabetic nephropathy. Activation of protein kinase C (PKC) is implicated to be one of the causal factors in the development of renal dysfunctions in diabetes. In this study, we have demonstrated that total diacylglycerol (DAG) contents and PKC activity in glomeruli were significantly increased in diabetic rats as compared to control rats, but intraperitoneal injection of d-alpha-tocopherol prevented these biochemical abnormalities in parallel with normalization of glomerular dysfunction such as increased glomerular filtration rate (GFR) in diabetic rats. Albuminuria in diabetic rats was also significantly increased as compared to control rats, whereas d-alpha-tocopherol treatment again ameriolated increased albuminuria in parallel with the inhibition of glomerular PKC activation by diabetes. Moreover, we have observed that the activity of DAG kinase, which metabolizes DAG to phosphatidic acid and acts as an attenuator for the DAG-PKC pathway, was enhanced by d-alpha-tocopherol treatment. These results suggest that the increase in the DAG-PKC pathway might play an important role for the development of glomerular dysfunctions in diabetes and d-alpha-tocopherol treatment could be helpful in diabetic nephropathy.

Mechanism of the progression of diabetic nephropathy to renal failure

Although the evolution of diabetic nephropathy is brought about mostly by persistent hyperglycemia, its progression may be influenced by various other factors such as hypertension and dietary protein intake. It has been recently suggested in the literature that the gene polymorphism of angiotensin converting enzyme (ACE) might be associated with the development of diabetic nephropathy, because the DD genotype of ACE gene is closely associated with the presence of nephropathy in diabetic subjects. However, in our present analysis the frequency of the DD genotype in patients with non-insulin dependent diabetes is not significantly related to the presence or absence of nephropathy. It remains to be clarified by multi-center analysis using large numbers of patients whether the gene polymorphism of ACE is related to the progression of diabetic nephropathy to renal failure. Furthermore, it has been postulated that the interstitial fibrosis evaluated in renal biopsy specimens is significantly correlated with the declining of renal function in diabetic patients. However, it is not possible to clinically quantitate the interstitial fibrosis without performing renal biopsy. We have recently found that the urinary excretion of type IV collagen is significantly increased in diabetic patients. Moreover, the increase in urinary type IV collagen is well correlated with the amount of urinary albumin. Since type IV collagen in the urine is probably derived from tubulointerstitial tissue, it is likely that the increased amount of type IV collagen in the urine may reflect the fibrotic change in diabetic kidneys. Whether the increase in urinary type IV collagen is able to predict for the progression of diabetic nephropathy in the future should be examined.

Hepatic injury localized to the field of total lymphoid irradiation

A 37-year-old woman with severe aplastic anemia underwent allogeneic bone marrow transplantation following cyclophosphamide (CY) and total lymphoid irradiation (TLI). On day +30, a CT scan was carried out because of a mild elevation in liver enzymes, and it revealed a low density area with a sharp border in the left lobe corresponding to the irradiated area. MRI showed a hypersignal intensity on both T1 and T2-weighted images and suggested that hepatic damage was mainly severe fatty change. These abnormalities resolved with no treatment. CY with TLI for adult patients with severe aplastic anemia may induce hepatic injury.

Beraprost sodium, an analogue of prostacyclin, induces the expression of mitogen-activated protein kinase phosphatase and inhibits the proliferation of cultured mesangial cells

Beraprost sodium, an analogue of prostacyclin, increases intracellular cyclic adenosine monophosphate (cAMP) in cultured glomerular mesangial cells. We examined the effect of beraprost on mesangial cell proliferation. Beraprost was able to inhibit fetal bovine serum-stimulated proliferation of mesangial cells in concentrations enough to increase cellular cAMP. By northern blot analysis, beraprost induced the expression of MKP-1, a mitogen-activated protein kinase phosphatase, in a dose- and time-dependent manner, similarly to dibutyryl cAMP and adrenomedullin. These results indicate that beraprost inhibits the proliferation of mesangial cells and one of the mechanisms might be cAMP-dependent induction of MKP-1.

Unrelated bone marrow transplantation from the National Marrow Donor Program

Between November 1992 and December 1996, we carried out bone marrow transplantation through the National Marrow Donor Program (NMDP) for 11 patients who lacked an appropriate donor among their family members and the Japan Marrow Donor Program (JMDP). They accounted for 11% of 101 patients who had registrated to the NMDP Transplant Center Office in Japan. The median time required from the initiation of preliminary search to transplant for these 11 patients was 198 days. The 11 donors included four Caucasians, one Native American and the others were Asian/Pacific islanders. A median of 17 h was required to transport bone marrow from harvest institutes to our hospital and their viability determined in our laboratory had a median of 96%. Engraftment was observed in all recipients and the incidence of grade III-IV acute graft-versus host disease was 27%. Of four patients three (75%) with chronic myelogenous leukemia in chronic phase (standard-risk) and two (29%) of seven patients in progressive state of the disease (high-risk), are alive at present. Cooperation between the JMDP and the NMDP, which began in April 1997, could shorten the time for donor search and allow transplantation to more patients with more appropriate timing.

Role of metal cations in the regulation of NADP-linked isocitrate dehydrogenase from porcine heart

The regulatory role of divalent metal cations in the NADP-linked isocitrate dehydrogenase (EC 1.1.1.42) from porcine heart was analysed. Saturation curves with respect to the substrate threo-DS-isocitrate complexed with the metals including manganous, cadmium, cobaltous and zinc ions showed sigmoid relationships characteristic of allosteric enzymes. The Hill's interaction coefficients were 1.90, 1.75, 1.28 and 1.12, respectively. Saturation kinetics of the substrate-metal complexes including magnesium, ferrous and nickel ions exhibited normal hyperbolic curves with Hill's coefficients of 1. The ionic radii of metal cations were closely correlated with the maximal velocity, the enzyme affinity and the Hill's n11 values for the substrate-metal complexes. Cooperative interactions of metal-substrate complexes with NADP-isocitrate dehydrogenase are discussed in relation to the sites of the enzyme for the binding of the metal-substrate complex.

Distribution of heparin-binding EGF-like growth factor protein and mRNA in the normal rat kidneys

Heparin-binding EGF-like growth factor (HB-EGF), a newly discovered potent mitogen and chemoattractant for smooth muscle cells, is a member of the EGF superfamily and binds to EGF receptors. To investigate the role of HB-EGF in the kidney, we determined the distribution of HB-EGF immunohistochemically in normal rat kidneys. The localization of mRNA expression was also studied by in situ hybridization, using a synthesized digoxigenin-labeled anti-sense riboprobe of HB-EGF. Immunohistochemical and in situ hybridization studies revealed that the tubular epithelial cells of the S3 segment of the outer stripe in the outer medulla were the predominant renal source of HB-EGF. In addition, in the immunohistochemical analysis, HB-EGF was ubiquitously present in the epithelial cells of the proximal tubules and the arterial smooth muscle cells, while HB-EGF expression was not detected in other parts of the kidney, including the glomeruli. Although EGF receptors were found to be present in the proximal tubules as well as in the distal tubules and collecting ducts, EGF has not been found to be expressed in the proximal tubules. Therefore, the present results indicate that HB-EGF might be a ligand for EGF receptors in the proximal tubules and might play a role in the functions of proximal tubules.

Mitogen-activated protein kinase cascade is activated in glomeruli of diabetic rats and glomerular mesangial cells cultured under high glucose conditions

The activation of protein kinase C (PKC) found in diabetic glomeruli and glomerular mesangial cells cultured under high glucose conditions has been proposed to contribute to the development of diabetic nephropathy. However, the abnormalities distal to PKC have not been fully elucidated yet. Herein, we provide the evidence that mitogen-activated protein kinase (MAPK) cascade, an important kinase cascade downstream to PKC and an activator of cytosolic phospholipase A2 (cPLA2) by direct phosphorylation, is activated in glomeruli isolated from streptozotocin-induced diabetic rats. MAPK cascade was also activated in glomerular mesangial cells cultured under high glucose (27.8 mmol/l) conditions for 5 days, and the activation of MAPK cascade was inhibited by treating the cells with calphostin C, an inhibitor of PKC. Furthermore, the activities of cPLA2 also increased in cells cultured under the same conditions and this activation was inhibited by both calphostin C and PD 098059, an inhibitor of MEK (MAPK or extracellular signal-regulated kinase [ERK] kinase). These results indicate that MAPK cascade is activated in glomeruli and mesangial cells under the diabetic state possibly through the activation of PKC. Activated MAPK, in turn, may induce various functional changes of mesangial cells at least through the activation of cPLA2 and contribute to the development of diabetic nephropathy.

Endothelin-1 activates c-Jun NH2-terminal kinase in mesangial cells

Endothelin-1 (ET-1) is known to induce the contraction and proliferation of glomerular mesangial cells. ET-1 has been shown to activate p42 and p44 mitogen-activated protein kinases (MAPKs), also known as extracellular signal regulated kinases (ERKs), through both protein kinase C (PKC) and protein tyrosine kinase (PTK)-dependent pathways. However, an involvement of c-Jun NH2-terminal kinase (JNK), one of members of the MAPK family, in ET-1 signaling in mesangial cells has not yet been elucidated. To clarify this point, we examined whether ET-1 could activate JNK and the mechanism of activation in cultured mesangial cells. ET-1 enhanced the activities of JNK in a dose-dependent (10(-8) M maximum) and time-dependent manner, with a peak at 15 minutes. ET-1-induced activation of JNK was blocked by BQ-123, an antagonist for the ETA receptor. The depletion of PKC by prolonged treatment with phorbol 12,13 dibutyrate or the inhibition of PKC by GF 109203X failed to inhibit ET-1-induced activation of JNK. In contrast, ET-1-induced activation of JNK was significantly reduced by calcium chelation (with BAPTA/AM and EGTA). In addition, ionomycin, a calcium ionophore, and thapsigargin, an intracellular calcium-rising agent, were able to induce the activation of JNK. ET-1-induced activation of JNK was also inhibited by PTK inhibitors (herbimycin A and genistein). Furthermore, ET-1 increased the DNA-binding activity of AP-1 containing c-Jun and c-Fos proteins. These results indicate that ET-1 is able to activate JNK in glomerular mesangial cells through PKC-independent and PTK-dependent pathways and intracellular calcium is necessary to the activation of JNK.

Microalbuminuria is not associated with cardiovascular death in Japanese NIDDM

To evaluate whether the presence of microalbuminuria can predict cardiovascular death in Japanese subjects with non-insulin-dependent diabetes mellitus (NIDDM), we investigated 297 Japanese NIDDM patients with Albustix-negative urine. Patients were divided into two groups, normoalbuminuric (n = 201) and microalbuminuric (n = 96) and followed until death or the end of 1994 (the mean follow-up period was 6.4 years). During the follow-up period, 28 deaths (14 normoalbuminuric and 14 microalbuminuric patients) were confirmed and only 10 deaths were attributed to cardiovascular disease (6 normoalbuminuric and 4 microalbuminuric patients). Although the age- and sex-adjusted mortality rate from all-causes in the microalbuminuric group was significantly higher than that in the normoalbuminuric group (13.5 vs. 8.2 per 1000 person-years: P < 0.05), the mortality rate from cardiovascular disease was not significantly different between two groups (3.4 vs. 3.3 per 1000 person-years). On age-adjusted Cox proportional hazards analysis. HbA1c and triglyceride were independent risk factors in mortality from cardiovascular disease, while microalbuminuria was not associated with cardiovascular death. These results indicate that, unlike Caucasians, the presence of microalbuminuria can not predict cardiovascular death in Japanese subjects with NIDDM.

[Studies on type IV collagen production in cultured mesangial cells]

Mesangial expansion is one of the histological abnormalities observed among the various glomerular diseases. It is due largely to the accumulation of extracellular matrix (ECM) proteins, such as type IV collagen, laminin and fibronectin. In order to examine the abilities of mesangial cells to produce type IV collagen, we used enzyme-linked immunosorbent assay to measure type IV collagen secreted from cultured rat mesangial cells. After exposing confluent cells to endothelin-1 (ET-1, 0.01 microM), insulin-like growth factor-1 (100 ng/ml) angiotensin-II (1 microM) and transforming growth factor-beta (1 ng/ml) for 24 hours, type IV collagen production increased 1.5 approximately 2.5 times. ET-1 stimulated type IV collagen production in a dose-dependent fashion, and this effect was blocked by the protein kinase C inhibitor, staurosporine. Atrial natriuretic peptide (ANP) inhibited the increase in type IV collagen production caused by ET-1 in a dose-dependent fashion. Addition of 8-bromo-cGMP similarly suppressed the stimulation of type IV collagen production caused by ET-1. These findings indicate that ET-1 stimulates type IV collagen synthesis in cultured rat mesangial cells by a mechanism probably involving activation of PKC, and that ANP inhibits ET-1-induced production of type IV collagen through a cGMP-dependent process.

[Relationship between the stage of diabetic nephropathy and serum lipoprotein (a) concentrations--influence of hypoproteinemia]

Lipoprotein (a) [Lp(a)] has been reported to be an independent risk factor for coronary heart disease. Elevated levels of Lp(a) in diabetic subjects have also been reported, especially in subjects with nephropathy. However, the mechanism and the clinical implication of Lp(a) elevation in diabetics remain obscure. In the present study, to verify the change in Lp(a) concentration with the progression of nephropathy, serum Lp(a) levels were measured in 546 NIDDM patients, 33 hemodialysis NIDDM patients, and 145 non-diabetic controls.

RESULTS

1) The serum Lp(a) levels in diabetics were significantly higher than those in the non-diabetic controls. 2) Serum Lp(a) concentrations in microalbuminuric subjects were significantly higher than those in normoalbuminuric subjects, and were further increased in macroalbuminuric subjects. 3) In macroalbuminuric subjects, serum Lp(a) concentrations were inversely correlated with serum protein concentrations, but not with serum creatinine. 4) Once hemodialysis was started, the decrement of both serum Lp (a) and LDL-C concentrations were associated with the increment of serum protein concentrations. These data indicate that elevation of serum Lp (a) concentration in overt nephropathy could be, at least in part, due to hypoproteinemia.

Differential inhibition of mesangial MAP kinase cascade by cyclic nucleotides

The agents which increase intracellular cyclic AMP (cAMP) or cyclic GMP (cGMP) have been found to counteract the effects of the vasoconstrictive agents such as endothelin-1 (ET-1). To clarify the mechanism of this interaction, we evaluated the activities of mitogen-activated protein kinase (MAPK) cascade, one of the important signal transduction system of ET-1. Beraprost sodium, an analogue of PGI2, and adrenomedullin, a cAMP-raising agent, inhibited ET-1-induced activation of MAPK. Dibutyryl cAMP (Bt2-cAMP) and 8-bromo-cGMP (8-Br-cGMP), cell permeable analogues of cAMP and cGMP, were also able to inhibit the activation of MAPK and MAPK kinase (MAPKK) by ET-1 without interfering basal activities. In contrast, phorbol 12, 13-dibutylate (PDBu)-induced activation of MAPK and MAPKK was inhibited by Bt2-cAMP but not by 8-Br-cGMP. Interestingly, atrial natriuretic peptide (ANP) partially inhibited PDBu-induced activation of MAPK and MAPKK. These results indicate that cAMP and cGMP inhibit ET-1-induced activation of MAPK in cultured mesangial cells at different steps; the former might inhibit at a step downstream of PKC and the latter prior to PKC. The data also suggest that ANP might have cGMP-independent effect on MAPK.

[Tyrosine phosphorylation of focal adhesion kinase (p125FAK) and paxillin in glomeruli from diabetic rats]

Focal adhesion kinase (p125FAK) is a novel non-receptor cytosolic tyrosine kinase which is activated through the phosphorylation of its tyrosine residue by ligands that bind to integrins and ligands that activate protein kinase C (PKC). In diabetic glomeruli, extracellular matrix proteins such as fibronectin, laminin and type IV collagen, which bind to integrins, were found to be increased in the mesangial area. Furthermore, PKC was shown to be activated in diabetic glomeruli. These changes might be able to cause the activation of p125FAK in diabetic glomeruli. To test this hypothesis, we examined tyrosine phosphorylation of p125FAK and paxillin, a proposed substrate of p125FAK, in glomeruli isolated from streptozotocin (STZ)-induced diabetic rats. Tyrosine phosphorylation of p125FAK or paxillin was evaluated by immunoblot analysis using anti-phosphotyrosine antibody after immunoprecipitation with anti-p125FAK or anti-paxillin antibody. Three and seven weeks after STZ injection, tyrosine phosphorylation of both p125FAK and paxillin was increased in diabetic glomeruli. The increase in tyrosine phosphorylation of p125FAK and paxillin was not observed in glomeruli from diabetic rats treated with insulin. To investigate the mechanism of increase in tyrosine phosphorylation of p125FAK, we examined tyrosine phosphorylation of p125FAK in mesangial cells plated on a fibronectin-coated dish or cultured under conditions of high glucose concentration (conditions under which PKC can be activated). Attachment of the cells to fibronectin induced tyrosine phosphorylation of p125FAK, while a high glucose concentration did not modulate tyrosine phosphorylation of p125FAK. In conclusion, tyrosine phosphorylation of p125FAK and paxillin was increased in diabetic glomeruli and these alternations may have been caused by changes in extracellular matrix proteins in diabetes.

Atrial natriuretic peptide induces the expression of MKP-1, a mitogen-activated protein kinase phosphatase, in glomerular mesangial cells

Atrial natriuretic peptide (ANP) has been shown to inhibit the proliferation of various types of cells including glomerular mesangial cells. The activation of mitogen-activated protein kinase (MAPK) is one of the main signal transduction systems leading to cell proliferation. MAPK is tightly regulated by the activating kinase, MEK, and specific phosphatase MKP-1. Constitutive expression of MKP-1 has been shown to inhibit cell proliferation by suppressing MAPK activity. In order to understand the mechanism of the anti-proliferative effect of ANP, we examined whether ANP could inhibit MAPK by inducing MKP-1 in cultured rat glomerular mesangial cells. ANP increased the expression of MKP-1 mRNA in a dose-dependent (10 nM maximum) and time-dependent, with a peak stimulation at 30 min, manner. Receptor for ANP is a transmembrane guanylyl cyclase. Activation of guanylyl cyclase of ANP receptor by ligand plays an essential role in ANP signal transduction. 8-Bromo-cGMP, a cell permeable analogue of cyclic GMP, and sodium nitroprusside, an activator of soluble guanylyl cyclase, could mimic the effects of ANP and were able to induce the expression of MKP-1 in a similar time course as ANP. The protein expression of MKP-1 was maximally stimulated by ANP at 120 min. Treatment of the cells with ANP for 120 min resulted in an inhibition of phorbol ester-induced activation of MAPK, while the activation of MEK was not affected by ANP. These results indicate that ANP might inhibit the proliferation of mesangial cells by inactivating MAPK through the induction of MKP-1.

Breakthrough times for vapors of organic solvents with low boiling points in steady-state and pulsating flows on respirator cartridges

The breakthrough times of five organic solvents at various vapor concentrations were measured in steady-state and pulsating flows on commercially available respirator cartridges. The relationship between the logarithmic vapor concentration and the logarithmic breakthrough time of each organic solvent showed an inverse correlation in both of the flow patterns. The organic solvents with lower boiling points exhibited the shorter breakthrough times in both of the flow patterns. The ratios of the breakthrough times in the pulsating flow to those in the steady-state flow were lower than 0.9 when the vapor concentrations were higher than 600 ppm for ethyl acetate, methyl acetate, acetone and dichloromethane. From the present study, the breakthrough in the pulsating flow tends to occur earlier than in the steady-state flow when using a highly concentrated vapor of an organic solvent with a low boiling point.

Endothelin-1 stimulates tyrosine phosphorylation of p125 focal adhesion kinase in mesangial cells

Endothelin-1 (ET-1) is known to induce the contraction and proliferation of glomerular mesangial cells. Because ET-1 was found to stimulate the tyrosine phosphorylation of unidentified cellular proteins in cultured mesangial cells, protein tyrosine kinase might serve as one of the important signals leading to various functions of ET-1. Focal adhesion kinase (p125FAK) is a newly identified cytoplasmic protein tyrosine kinase that is activated by the phosphorylation of its own tyrosine residue. Because p125FAK was found to play a role in the signal transduction of not only integrins but also various neurotransmitters, including bombesin, endothelin, and vasopressin in Swiss 3T3 cells and Rat-1 fibroblasts, whether ET-1 could stimulate the tyrosine phosphorylation of p125FAK in glomerular mesangial cells was examined. ET-1 stimulated the tyrosine phosphorylation of p125FAK by threefold to fourfold in cultured mesangial cells. This effect of ET-1 was detected at 1 min and reached a maximum within 5 min and was blocked by BQ-123, an antagonist for ETA receptor. A23187, a calcium ionophore, failed to stimulate the tyrosine phosphorylation of p125FAK, and ET-1 was able to stimulate the tyrosine phosphorylation of p125FAK, even in a calcium-free medium. The activation of protein kinase C (PKC) by phorbol 12, 13-dibutyrate resulted in a stimulation of the tyrosine phosphorylation of p125FAK, and an inhibition of PKC by calphostin C or staurosporine significantly reduced the effect of ET-1. Furthermore, prolonged treatment of the cells with phorbol 12, 13-dibutyrate markedly inhibited the ET-1-induced tyrosine phosphorylation of p125FAK. These results indicate that p125FAK might play a role in a signal transduction system of ET-1 in glomerular mesangial cells and that the ET-1-induced tyrosine phosphorylation of p125FAK is largely dependent on the PKC pathway.

Abnormalities in protein kinase C and MAP kinase cascade in mesangial cells cultured under high glucose conditions

In order to clarify the mechanism of mesangial cell dysfunction in diabetes, we examined the activities of protein kinase C (PKC) and mitogen-activated protein kinase (MAPK), important kinases in various cellular functions, and also evaluated the isoenzymes of PKC in mesangial cells cultured under high glucose conditions. Exposure of cells to high concentrations (27.8 mM) of glucose for 5 days resulted in a significant elevation of PKC activities in the membrane fraction. MAPK was also activated in cells cultured under high glucose conditions. Of the PKC isoenzymes, the levels of PKC alpha and zeta were significantly increased in the membrane fraction after 5 days of exposure to high concentrations of glucose. These results indicate that the translocation of PKC alpha and zeta and the activation of MAPK under high glucose conditions might be underlying mechanisms of the functional disturbance of mesangial cells in diabetes.

Microalbuminuria cannot predict cardiovascular death in Japanese subjects with non-insulin-dependent diabetes mellitus

In order to examine whether the existence of microalbuminuria can predict the development of overt proteinuria and cardiovascular death in Japanese subjects with non-insulin-dependent diabetes mellitus (NIDDM), we investigated 47 patients for a 10-year follow-up period. Patients were divided into two groups by the initial values of urinary albumin excretion rates. The percentage of patients who developed overt proteinuria during the follow-up period was significantly higher in patients who were initially classified as microalbuminuric group (63.6%) than in normoalbuminuric group (17.4%). During the follow-up period, one of the patients with normoalbuminuria had died of congestive heart failure, while four of those with microalbuminuria had died; one of stroke and three from noncardiovascular diseases. These results indicate that the existence of microalbuminuria had the predictive power for the development of overt proteinuria, but not for cardiovascular death in Japanese subjects with NIDDM.

Cyclic nucleotides attenuate endothelin-1-induced activation of mitogen-activated protein kinase in cultured rat mesangial cells

In order to clarify the mechanisms of interaction between endothelin-1 (ET-1) and cyclic AMP (cAMP) or cyclic GMP (cGMP), we examined the effects of cAMP or cGMP on ET-1-induced activation of mitogen-activated protein kinase (MAPK), one of the key enzymes in the signal transduction of ET-1, in cultured rat mesangial cells. ET-1 was able to activate both p42 and p44 MAP kinases in a dose-dependent manner. Cell permeable analogues of cAMP and cGMP, dibutylyl cAMP (BT2-cAMP) and 8 bromo cGMP (8br-GMP), significantly inhibited ET-1-induced activation of MAPK. Atrial natriuretic peptide (ANP), which increased cellular cGMP, was able to inhibit ET-1-induced activation of MAPK in a dose-dependent manner, while c-ANP, an analogue specific to the clearance receptors of ANP, exerted no effect. These results indicate that cAMP and cGMP could modulate the action of ET-1 in mesangial cells at a step of the activation of MAPK.

Prevention of glomerular hyperfiltration in rats with streptozotocin-induced diabetes by an atrial natriuretic peptide receptor antagonist

The contribution of atrial natriuretic peptide (ANP) to the development of glomerular hyperfiltration in diabetes was investigated by examining the effects of HS-142-1, a non-peptide antagonist of biological receptors for ANP, on glomerular filtration rate (GFR) and renal plasma flow (RPF) in rats with streptozotocin-induced diabetes. Three to four weeks after streptozotocin injection, the plasma concentration of ANP, urinary cyclic GMP excretion rate, GFR, and RPF were significantly higher in diabetic rats than in control rats. The increase in GFR and RPF in diabetic rats was significantly reduced, in a dose-dependent manner, by a single intravenous injection of HS-142-1; the maximal effect was apparent at a dose of 10 mg per kg of body weight. Continuous subcutaneous administration of HS-142-1 with an osmotic minipump for 3 to 4 weeks, beginning 2 days after streptozotocin injection, prevented the increases in urinary cyclic GMP excretion rate, GFR, and RPF observed in untreated diabetic rats. These results highlight the importance of ANP in the development of diabetic glomerular hyperfiltration and indicate that this condition can be prevented by continuous inhibition of the action of ANP.