The aim of this study was to assess the role of urin ary dipeptidyl aminopeptidase N (DAP IV) in early diabetic nephropathy and impaired glucose tolerance (IGT). We compared urinary DAP N activity, N-acetyl-b-D-glucosaminidase (NAG) activity, and albumin levels between healthy subjects, non-insulin-dependent diabetic (NIDDM) subjects that did not show clinical proteinuria, and IGT subjects. In healthy subjects, a significant difference in the excretion of urinary DAP IV occurred with age. Therefore, we focused mainly on the results of the forties of each group. Urinary DAP IV activity in NIDDM subjects, and IGT subjects was significantly higher than that in controls (1 1.8 ± 5.3,7.2 ±1.4,5.7 ± 0.8 U/g creatinine (Cr), respectively, p <0.0 0 1). No statistically significant difference in urinary NAG activity was observed compared with controls (NIDDM; 4.5 ± 2.7, IGT; 3.7 ± 1.7, control; 2.9 ± 1.2 U/g Cr). A significant correlation was observed between urinary DAP N and urinary NAG in NIDDM and IGT groups. In both groups, some subjects showed elevated DAP N activity despite normal NAG activity, while no subjects showed both normal DAP IV activity and higher NAG activity. Urinary albumin levels in NIDDM subjects also were higher than those in controls (p < 0.0 1), but this difference was less pronounced than that for DAP IV activity (p < 0.0 0 1). We conclude that measurement of urinary DAP N activity is a useful tool for detecting early diabetic nephropathy.
To clarify the pathophysiology of the uremia-related immunodeficiency, we measured the lymphocytes subsets and their activation in autologous mixed lymphocyte reaction (AMLR), and evaluated the effect of recombinant erythropoietin (Epo) treatment in patients with chronic renal failure on hemodialysis (HD). We also engrafted their peripheral blood mononuclear cells (PBMC) to severe combined immunodeficient (SCID) mice to investigate PBMC function independently of the uremic milieu. Patients with HD had normal percentages of CD3+, CD4+ and CD8+ lymphocytes populations, but CD19+ cells decreased in number. However, serum interleukin-6 (IL-6) concentrations and the percentage of helper Ti (Thl) subpopulation increased, and the activation of CD3+ and CD4+ cells to AMLR reduced. After the treatment of Epo, the reduced activation of CD3 + and CD4 + cells in the AMLR was normalized. In SCID mice to which human PBMC were engrafted, human immunoglobulin and IL-6 concentrations in serum were not different between those with PBMC from patients on HD and mice with PBMC from normal controls. These data suggest that (1) the number of B lymphocytes decreases and that of Thl cells increase in patients on HD, (2) their CD3+ and CD4 + cell activation in the AMLR is reduced and that (3) the immunological abnormality can be returned to normal in several weeks when anemia or the uremia-related milieu is improved.
We examined the effects of smoking on plasma and platelet arginine vasopressin (AVP) levels, platelet aggregation with AVP, and AVP binding to platelets in normal subjects. Plasma and platelet AVP levels increased to the peak level at 5 to 10 min after the start of smoking, and decreased thereafter in parallel with plasma nicotine levels. A good correlation was found between plasma nicotine levels and plasma AVP levels, and also between plasma and platelet AVP levels. These results suggest that platelets rapidly take up endogenously released AVP from plathna. We also observed a decreased platelet aggregation with AVP ex vivo when the plasma and platelet AVP levels were elevated in vivo after somking. Binding experiments of washed platelets did not demonstrate any change in receptor number or affinity before and after smoking. These findings indicate that endogenously released AVP taken up by platelets desensitizes platelets to AVP without loss of AVP receptor number or modification of receptor affinity for AVP.
We found 3 subjects whose platelets lacked an aggregation response to arginine vasopressin (AVP) out of 36 healthy subjects. These 3 subjects (Non-Responders; NR) were compared with 8 subjects whose platelets responded completely to AVP (Responders; R). All cases were young healthy men without bleeding disorders or tendencies. Platelet function was evaluated by aggregation response to AVP, adenosine diphosphate (ADP), collagen, and epinephrine. Resting and AVP-stimulated [Ca2+]i in platelets were also measured. We measured AVP levels in platelet free plasma (PFP) and in platelets, and characterized AVP receptor on platelets. There were no significant differences in platelet aggregation with ADP, collagen, and epinephrine between the 2 groups. Addition of AVP to platelets showed a rapid but transient increase in [Ca2+]i in both groups, but the peak level was extremely low in NR. The binding experiment demonstrated that maximal binding capacity (B max) of AVP receptor on platelets was significantly reduced in NR (B max; 213 ± 12 SEM sites/cell in N vs.30 ± 4 sites/cell in NR). PFP and platelet AVP levels did not differ between the 2 groups. These results indicate that the selective lack of platelet aggregation with AVP is caused probably by congenitally reduced B max of AVP receptor.