SummaryThe activities and expression of protein kinase C isoenzymes were examined in glomerular mesangial cells cultured under high glucose conditions. Exposure of cells to high glucose concentrations (27.8 mmol/1) for more than 3 days resulted in a significant elevation of protein kinase C activities in the membrane fraction. Of the protein kinase C isoenzymes, the levels of protein kinase C ~ significantly increased in the membrane fraction after 3 days of exposure to glucose, and protein kinase C ( increased after 5 days of exposure. Levels of protein kinase C 6 and e remained unchanged and protein kinase C fl and ~ were not detected. These results indicate that protein kinase C a and ( are translocated under high glucose conditions possibly through different mechanisms. [Diabetologia (1994) 37: 838-841]

Peripheral blood mononuclear cells (PBMC) obtained from patients with lower respiratory infections were examined for the detection of human respiratory syncytial virus (RSV) sequences in the N region using the reverse transcription polymerase chain reaction (RT-PCR). RSV infection was confirmed by at least one method, i.e., virus isolation, enzyme immunoassay for viral antigen, and RT-PCR of nasopharyngeal secretions (NPS) samples. The detection rate for RSV RNA in PBMC obtained from RSV-infected patients was 40% (38/94), compared to 5% (1/20) in controls (P = 0.002). Between the groups positive (38) and negative (56) for RSV RNA in PBMC, there was no significant difference in clinical parameters. Seven patients had eight episodes of reinfection and RSV RNA was detected in 50% (4/8) during consecutive infections. Sequences of their PBMC samples were distinct from those of prototype strains of subgroup A and B. However, they were not always consistent with those of paired NPS samples. The findings suggested that RSV RNA could be detected in PBMC even during reinfection and as might have the possibility of quasispecies dynamics, reflecting the nature of RNA viruses.

SummaryTo determine whether increased oxidative stress in diabetes mellitus is due to an impaired freeradical scavenger function in endothelial cells, GSHdependent H202 degradation in human umbilical vein endothelial cells was studied. The GSH-dependent, NaN3-uninhibitable H202-degradation in endothelial cells was reduced by 48 % (p < 0.001) when the cells were exposed to 33 mmol/1 D-glucose vs 5.5 mmol/1 D-glucose. This impairment was dependent not only on the D-glucose concentration in the medium but also on D-glucose specific metabolism, since neither 27.5 mmol/1 L-glucose nor 27.5 mmol/1 D-raffinose had any effect on the peroxide degradation activity. Activation of the glutathione redox cycle by H202 in cells exposed to high glucose concentrations was attenuated as compared with 5.5 mmol/1 D-glucose because of: 1)a 42% decrease (p <0.001) in intracellular NADPH content, and 2) a 34 % reduction (p < 0.01) in glutathione release into the media. This results in an accumulation of GSSG in the cells following exposure to H202. Both H202-evoked 5~Cr-release and H202-induced endothelial cell damage were significantly (p < 0.01) greater in the 33 mmol/1 D-glucose group than in the 5.5 mmol/1 D-glucose group. These results indicate that the abnormal glutathione redox cycle observed in endothelial cells is induced by high glucose concentrations in the medium, resulting in an impairment of reduced GSH-dependent H202-degradation. These abnormalities may associate with the increased cellular damage following an exogenous exposure to H202. [Diabetologia (1994) 37: 264-269]

To investigate the difference of insulin action between skeletal muscle and adipose tissue in response to dietary manipulation, we studied the effect of high-sucrose (HS) and high-fat (HF) diet on insulin action by measuring insulin binding and insulin action both in soleus muscles and adipocytes. HS feeding led to a 14 and 28% decrease, and HF feeding led to a 25 and 36% decrease in insulin binding both to soleus muscles and adipocytes, respectively (P less than 0.01). In HF-fed rats, both rates of glucose uptake and intracellular glucose metabolism were impaired by 30-40% in soleus muscles (P less than 0.01), and adipocyte glucose uptake was also decreased by 30% in the submaximally insulin-stimulated state (P less than 0.05). On the other hand, in HS-fed rats with prominent hyperinsulinemia, glucose uptake was 2.3- to 2.7-fold increased in adipocytes (P less than 0.01). However, both rates of glucose uptake and intracellular glucose metabolism were not increased in soleus muscles from HS-fed rats. Steady-state plasma glucose (SSPG) level was unchanged in HS-fed rats during somatostatin, glucose, and insulin infusion, whereas the SSPG level of HF-fed rats was twice as much as that in controls (P less than 0.01). These results indicate that long-term regulation of glucose metabolism by ambient insulin in skeletal muscle may be different from that in adipocytes and that insulin action in muscle, rather than in adipocyte, may reflect insulin action of whole body.

SummaryThe 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 ANR 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 ANR 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 ANR [Diabetologia (1995) 38: 536-542] Key words Diabetic nephropathy, atrial natriuretic peptide, atrial natriuretic peptide receptor antagonist, glomerular hyperfiltration. Glomerular hyperfiltration is observed in early stages of both human [1,2] and experimental diabetes [3,4] and has been postulated to be associated with subsequent development of diabetic nephropathy [5,6]. Thus, it is important to clarify the pathogenetic mechanism of glomerular hyperfiltration. Among possible mechanisms, atrial natriuretic peptide (ANP) has been suggested to mediate glomerular hyperfiltration in diabetes, because plasma ANP concentration was shown to be increased in diabetic rats with glomerular hyperfiltra-