The role of protein-tyrosine phosphatase 1B (PTP1B) in diabetes was investigated using an antisense oligonucleotide in ob͞ob and db͞db mice. PTP1B antisense oligonucleotide treatment normalized plasma glucose levels, postprandial glucose excursion, and HbA 1C. Hyperinsulinemia was also reduced with improved insulin sensitivity. PTP1B protein and mRNA were reduced in liver and fat with no effect in skeletal muscle. Insulin signaling proteins, insulin receptor substrate 2 and phosphatidylinositol 3 (PI3)-kinase regulatory subunit p50␣, were increased and PI3-kinase p85␣ expression was decreased in liver and fat. These changes in protein expression correlated with increased insulin-stimulated protein kinase B phosphorylation. The expression of liver gluconeogenic enzymes, phosphoenolpyruvate carboxykinase, and fructose-1,6-bisphosphatase was also down-regulated. These findings suggest that PTP1B modulates insulin signaling in liver and fat, and that therapeutic modalities targeting PTP1B inhibition may have clinical benefit in type 2 diabetes.

Blockade of the renin-angiotensin system was studied in male Sprague-Dawley rats during long-term inhibition of nitric oxide synthase. Nitro-L-arginine-methyl ester (L-NAME) was placed in the drinking water for 4 weeks (-100 nig/kg per day). Separate groups of rats were coadministered the angiotensin II antagonist A-81988 in the drinking water ranging from approximately 0.001 to 1 ing/kg per day. Control groups received only tap water or A-81988 alone. Each week, rats were placed in metabolic cages, and tail-cuff blood pressures and blood samples were taken. L-NAME produced a sustained elevation in tail-cuff pressure that was completely prevented by A-81988. No changes in creatinine clearance, sodium excretion, plasma creatinine concentration, or blood urea nitrogen were observed. Food and water intakes were identical in all groups. Water excretion was significantly increased in L-NAME-treated animals regardless of additional inhibitor treatment, suggesting a possible role for nitric oxide synthase in the control of water excretion; this effect was independent of blood pressure. Although less potent than A-81988, the angiotensin II antagonist losartan and the angiotensin converting enzyme inhibitor enalapril also blocked L-NAME-induced hypertension. In a separate series of experiments, rats were not given A-81988 until 2 weeks after hypertension had fully developed in L-NAME-treated rats. Within 1 week of treatment with the angiotensin II antagonist, tail-cuff pressure returned to normal. We conclude from these studies that long-term inhibition of endogenous nitric oxide production produces an angiotensin II-dependent form of hypertension. {Hypertension 1993;21:660-666) KEY WORDS • endothelium-derived relaxing factor • nitro-L-arginine-methyl ester • hypertension, essential • angiotensin converting enzyme inhibitors • renin-angiotensin system • kidney • rat studies • renal function T he endothelium-derived relaxing factor nitric oxide (NO) appears to play a significant role in the regulation of renal and systemic hemodynamics. One line of evidence that supports such a role is the observation of increased vascular resistance and blood pressure after acute inhibition of NO synthase, the enzyme responsible for production of NO and L-citrulline from L-arginine and oxygen.1 Recently, it has been reported that long-term inhibition of NO synthase will produce a sustained hypertension in otherwise normotensive rats or dogs.2 -4 This prolonged hypertension was associated with a mild degree of renal failure, as evidenced by decreases in glomerular filtration rate (GFR), proteinuria, and glomerular sclerotic injury. -4In addition to the enzyme present in vascular endothelium (type III), several isoforms of NO synthase have been identified in a variety of tissues, including the brain (type I).5 " 8 Interestingly, type I NO synthase is present in regions of the hypothalamus thought to be important in fluid-volume regulation, which suggests a role for this isoform in the central nervous

Experiments were designed to examine the role of endothelin (ET) receptors, specifically ETA receptors, in mediating the renal vasoconstrictor effects of ET-1 in anesthetized Sprague-Dawley rats. Intravenous infusion of ET-1 at 25 pmol.kg-1 x min-1 for 60 min produced a significant increase in mean arterial pressure (20 +/- 7%) and decreases in renal plasma flow (-60 +/- 6%) and glomerular filtration rate (-47 +/- 6%). Renal vascular resistance was significantly increased from 17 +/- 1 mmHg.ml-1 x min.g kidney wt during control period to 54 +/- 11 mmHg.ml-1 x min.g kidney wt during the experimental period. A second group of rats was infused with both ET-1 and the specific ETA receptor antagonist BQ-123 (0.1 mg.kg-1 x min-1). ET-1-induced increases in mean arterial pressure were completely blocked by BQ-123 (the average change was -7 +/- 4%). However, the renal vasoconstrictor effects of ET-1 were not affected by the antagonist, since renal plasma flow and glomerular filtration rate were again significantly reduced (-54 +/- 4 and -56 +/- 6%, respectively). Once again, renal vascular resistance was significantly increased from 16 +/- 2 mmHg.ml-1 x min.g kidney wt during the control period to 33 +/- 5 mmHg.ml-1 x min.g kidney wt during the experimental period. In a third group, infusion of BQ-123 alone produced a significant decline in mean arterial pressure (-13 +/- 2%), with no significant changes in renal plasma flow or glomerular filtration rate, thus producing a significant decrease in renal vascular resistance (15 +/- 1 vs. 11 +/- 2 mmHg.ml-1 x min.g kidney wt).(ABSTRACT TRUNCATED AT 250 WORDS)

The putative endothelin-converting enzyme (ECE) has been the focus of intense research, both within academia and the pharmaceutical industry. Interest in ECE stems mainly from the hypothesis that development of inhibitors of ECE will provide an effective means of preventing production of endothelin in circumstances where it may play a pathogenic role. Both an aspartic and a metalloprotease have been identified that have characteristics of this putative enzyme. Evidence suggests that the metalloprotease, which is inhibited by phosphoramidon, may be the physiologically relevant converting enzyme. However, it remains to be demonstrated conclusively that any inhibitor of an ECE activity directly alters endogenous endothelin production and/or the pathogenesis of a disease condition in which endothelin is thought to play a primary role.