Effects of sarpogrelate on serotonin-induced increases in cytosolic Ca2+ in cultured rat mesangial cells

The effects of the new 5-HT2A receptor antagonist sarpogrelate on the cellular action of serotonin were examined in cultured rat mesangial cells by measuring cytosolic free calcium concentration ([Ca2+]i). Sarpogrelate inhibited serotonin-induced increases in [Ca2+]i in a concentration-dependent manner. M1, a major metabolite of sarpogrelate, also exhibited an inhibitory effect exceeding that of sarpogrelate. The inhibitory effects of sarpogrelate and M1 were abolished by washing out these compounds. In contrast, the increase in [Ca2+]i induced by angiotensin II or arginine vasopressin was not affected by pretreatment of the cells with sarpogrelate or M1. These results suggest that sarpogrelate and its major metabolite (M1) act as reversible and specific 5-HT2A receptor antagonists against the contractile action of platelet-derived serotonin in mesangial cells.

Anaerobic threshold can provoke microalbuminuria in non-insulin-dependent diabetics

We examined two groups of non-insulin-dependent diabetic men (group A, 13 patients without microalbuminuria; group B, 9 patients with intermittent microalbuminuria) to ascertain whether the anaerobic threshold (AT) can provoke microalbuminuria, comparing them with 12 healthy subjects matched for age and sex (group C). All subjects exercised on a bicycle ergometer until the AT was reached. In intermittent microalbuminuria, the albumin:creatinine ratio (ACR) was over 0.25 mg/mmol.Cr 1-3-fold in 5 measurements. The ACR after exercise was increased to over 0.25 mg/mmol.Cr in 4/9 cases in group B (P < 0.05), in 2/13 cases in group A, but not at all in group C. We also studied the mechanism of exercise-induced microalbuminuria. In group B, ACR before exercise correlated positively with the baseline plasma glucose. Furthermore, positive correlation was found between ACR after exercise and HbA1c in group B. The AT did not affect the urinary beta 2-microglobulin in any groups. The plasma atrial natriuretic factor (ANF) after exercise was elevated most prominently in group B (P < 0.05). Positive correlation was found between increments of ACR and increments of plasma ANF after exercise in group B. We conclude that the AT can provoke microalbuminuria in some non-insulin-dependent diabetics. The plasma ANF and metabolic control may play an important role in the pathophysiology of exercise-induced microalbuminuria.

[Glomerular apolipoprotein B deposition in glomerular diseases]

In an attempt to elucidate the relationship between the progress of glomerular injury and abnormalities of lipid metabolism, we investigated glomerular deposition of apolipoprotein B (apo B) in renal biopsy specimens from 60 patients with glomerular diseases by indirect immunofluorescence using antihuman apo B-100 monoclonal antibody in comparison with clinical and histopathological findings. The patients were divided into 2 groups according to the intensity in staining of apo B in glomerulus (group A: negative or weakly positive; and group B: definitely positive). Staining of apo B in glomerulus was found in 37 patients (62%). The levels of serum total cholesterol, phospholipids, low density lipoprotein cholesterol and apo B in group B were significantly higher than in group A. The urinary protein excretion in group B was greater than that in group A. Group B was also shown to have a significantly decrease in renal function. Light microscopy revealed severe mesangial proliferation in patients with IgA nephropathy of group B. These findings suggested that glomerular apo B containing-lipoprotein deposition may play an important role in the progression of glomerular injury.

Relationship between age-adjusted heart rate and anaerobic threshold in estimating exercise intensity in diabetics

We compared heart rates at the anaerobic threshold (AT) with age-adjusted heart rates in two groups of diabetics (DMY, mean age 31; and DMO, mean age 48) to ascertain whether the AT is useful for evaluating the intensity of exercise therapy for diabetics. In both the DMY and DMO groups the AT was reached at lower heart rates than in control groups of healthy subjects, indicating that the metabolism of diabetics may become anaerobic if their age-adjusted heart rate is higher than their heart rate at the AT. In this study, 86% of the DMY and 50% of the DMO group had age-adjusted heart rates, at 70% of maximum, that were higher than the heart rates at the AT. Thus, exercise intensity with an age-adjusted heart rate at 70% of maximum may induce anaerobic metabolism in some diabetics. We also studied the relationship between exercise intensity and the glycosylated hemoglobin (HbA1c) level at the AT in order to understand why the heart rate at the AT in diabetics was less than in healthy subjects. Exercise intensity at the AT in both diabetic groups was less than in healthy groups, and so did not increase the heart rates. Both exercise intensity and the heart rate at the AT were inversely related to the HbA1c level, suggesting that HbA1c may be important for keeping low the exercise intensity and the heart rate at the AT. As far as possible, we excluded cardiovascular autonomic neuropathy, so that it could not explain the mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of calcium in suppression of glucagon release from isolated diabetic rat pancreata

To investigate the role of extracellular Ca2+ (Ca2+) in suppression of glucagon release in diabetic animals, pancreata were isolated from streptozotocin-diabetic rats and perfused with a 15 mM glucose solution containing one of the following: (1) Ca2+ 2.1 mM and insulin 22 microU/ml, (2) Ca2+ 2.1 mM and insulin 110 microU/ml, (3) Ca2+ 2.1 mM and insulin (-) or (4) Ca2+ 0.2 mM and insulin 110 microU/ml. Although perfusion with 22 microU/ml of insulin did not alter glucagon release, perfusion with 110 microU/ml of insulin in the presence of Ca2+ and glucose significantly reduced the release of glucagon from 1.9 +/- 0.3 ng/min to 1.2 +/- 0.3 ng/min for the first 3 min. The absence of insulin enhanced glucagon release from the baseline level of 1.0 +/- 0.1 ng/min to 1.6 +/- 0.3 ng/min at 11 min and to 1.4 +/- 0.2 ng/min at 21 min. Deprivation of Ca2+ in the perfusate also enhanced glucagon release from the baseline level of 0.8 +/- 0.1 ng/min to 1.2 +/- 0.3 ng/min for the first 4 min. It is concluded that insulin suppresses glucagon release and Ca2+ is needed for the suppression of glucagon release in the presence of both insulin and glucose in streptozotocin-diabetic rat pancreata.

On the origin of alpha-glucosidase in human urine

The recent findings that alpha-glucosidase from human kidney was identical with one component (F1) of the alpha-glucosidases found in human urine suggested the idea that this enzyme might originate in the kidneys. The present study was performed to test this idea by immunological methods. Urine alpha-glucosidase F1 was isolated in the electrophoretically homogeneous state, and the antibody prepared in rabbits was purified by affinity chromatography after the antisera were fractionally precipitated with ammonium sulfate and chromatographed on diethylamino ethyl (DEAE)-cellulose. The staining of human kidney tissue sections was performed by the indirect method, using alpha-glucosidase F1 antibody and fluorescein-conjugated anti-rabbit immunoglobulin goat sera. The proximal convoluted portion (proximal tubules) with brush border and Henle's loops (late proximal) were stained clearly. Preincubation of intact antibody with purified antigen prevented specific staining of the proximal convoluted portion and Henle's loops. In contrast, all other tissues of kidney were stained less positively or negatively. These results indicate that alpha-glucosidase F1 originates in the kidney, and that glucosidase is specifically localized in the proximal convoluted portion and Henle's loops.

Identity of alpha-glucosidase of human kidney with urine F-1 alpha-glucosidase

alpha-Glucosidase was extracted from a homogenate of human kidney, initially with 0.02 M Tris-HCl buffer, pH 7.6, and subsequently with a mixture of 0.5% cholate and 0.5% Triton X-100 in the same buffer, pH 7.6. The enzyme in each of these two fractions was purified to the electrophoretically pure state by fractional precipitation with ammonium sulfate, column chromatographies on DEAE-cellulose, hydroxyapatite, Bio Gel A-1.5 m and affinity chromatography on heated glutinous rice. The two purified alpha-glucosidase preparations obtained were the same in enzymatic and proteochemical properties, and the molecular weight and isoelectric point estimated were 3 x 10(5) and 4.2, respectively. No evidence for subunit structure was obtained. The optimum pH for activity was 5.6 and the activity was drastically inhibited by Nojirimycin. The alpha-glucosidase readily hydrolyzed maltose, starch, and glycogen, producing only glucose. It hydrolyzed maltotriitol to split the non-reducing end glucose, but scarcely hydrolyzed maltitol or various other heteroglucosides examined. All these proteochemical and enzymatic properties of kidney alpha-glucosidase were the same as those of urine F-1 alpha-glucosidase. Also, kidney tissue alpha-glucosidase produced a clear precipitin line with antisera against urine F-1 alpha-glucosidase. These facts suggest that F-1 alpha-glucosidase in urine originates from kidney tissue.

Clinical study of niceritrol on serum lipids in the treatment of hyperlipidemia

The effects of niceritrol, a nicotinic acid derivative, on the levels of HDL-cholesterol (HDL-Ch) and a mixture of VLDL- and LDL-Ch (VLDL- + LDL-Ch) were studied in hyperlipidemic patients. Serum total cholesterol (sTC) and serum triglyceride (sTG) were significantly reduced during niceritrol administration. Lipoprotein electrophoresis showed that niceritrol increased the alpha:beta ratio. HDL-Ch showed a significant increase of 12.5% by the 16th week of therapy. This increase was more marked in patients with lower pre-treatment HDL-Ch levels and significant in patients whose pre-treatment sTG levels were in excess of 200 mg/dl. Females displayed higher pre-treatment HDL-Ch levels (38.5 mg/dl) than males (30.6 mg/dl). However, niceritrol increased HDL-Ch significantly in both groups. At 16 weeks, the VLDL- + LDL-Ch level showed a significant decrease of 9.2%; the HDL-Ch:VLDL + LDL-Ch and HDL-CH:sTC ratios were significantly increased throughout niceritrol administration. Niceritrol is thought to be effective in preventing the development and progression of atherosclerosis because it raises the level of anti-atherogenic HDL-Ch and lowers the level of atherogenic VLDL- + LDL-Ch.