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Biomedical subjects

A Itabashi

Publications and source records attributed to A Itabashi.

16 recordsLinked to original sources
PubMed1991

Effect of alpha 1-blockade on diminished forearm blood flow in diabetics.

An increased risk of atherosclerotic disease has been reported in patients with diabetes mellitus. The present study was therefore designed to determine forearm blood flow (FBF) in patients with essential hypertension or those with diabetes mellitus with or without hypertension. FBF determined by venous occlusion plethysmography decreased with age in controls as well as in patients with essential hypertension, whereas FBF in diabetics was significantly lower irrespective of age or blood pressure. As a result, vascular resistance was significantly higher in diabetics than in controls or patients with essential hypertension. Glycemic control in normotensive diabetics during 3 weeks significantly augmented a diminished FBF. alpha 1-Blockade by oral administration of 1 mg of prazosin also augmented the diminished FBF in diabetics, in association with a significant decrease in mean blood pressure and vascular resistance. These results suggest that FBF may be a simple and useful index for determining arterial and/or venous distensibility, and that alpha 1-blocker therapy, in addition to glycemic control, may be a first-line antihypertensive treatment for diabetics with associated hypertension.

Administration, Oral↗
PubMed1991

Effect of dietary calcium on renal prostaglandins.

The present study was designed to clarify the possible role of renal prostaglandins (PGs) on blood pressure (BP) regulation during calcium (Ca) restriction or supplementation. Twelve normotensive women with a mean age of 21.2 years participated in the study. After 1 week of normal Ca intake (mean +/- SE, 536 +/- 2 mg/day), a low-Ca diet (163 +/- 1 mg/day) was given for a further 1 week. Additional asparagine Ca (3 g as Ca/day) was also given to half of the subjects. BP, heart rate, and serum total and ionized Ca concentrations were measured at the end of each period. Levels of Ca, sodium, PGE2, 6-keto-PGF1 alpha and thromboxane (TX) B2 excreted into urine were also determined. The plasma level of ionized Ca was significantly increased without any change in total Ca in both groups. Low and high Ca intake decreased and increased urinary Ca excretion by 28% and 56%, respectively. BP was not altered after Ca deprivation or loading. However, urinary PGE2 excretion was significantly augmented from 668.9 +/- 68.1 to 959.7 +/- 183.1 ng/day by Ca loading, whereas Ca deprivation decreased PGE2 excretion (695.4 +/- 108.1 to 513.2 +/- 55.2 ng/day). No changes were observed in 6-keto-PGF1 alpha or TXB2 urinary excretion. These results suggest that renal PGE2 synthesis is stimulated or decreased by 1-week Ca loading or deprivation, indicating a possible antihypertensive role of renal PGE2 during high-Ca intake in hypertensives.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Effect of dietary calcium on serum BGP (osteocalcin).

The present study was designed to clarify the effects of dietary calcium (Ca) intake on serum BGP (osteocalcin) levels. Twelve women with a mean age of 21.2 years participated in the study. After one week of normal Ca intake (mean +/- SE, 535 +/- 2 mg/day), a low-Ca diet (163 +/- 1 mg/day) was given for one further week. Additional asparagine Ca (3 g as Ca/day) was also given to half of the subjects. Serum total and ionized Ca concentrations as well as BGP, PTH and 1,25(OH)2D3 were measured at the end of each period. Amounts of Ca and hydroxyproline excreted in urine were also determined. The plasma level of ionized Ca was significantly increased without any change in total Ca in either group. Low and high Ca intake decreased and increased urinary Ca excretion by 28% and 56%, respectively. Serum levels of BGP and 1,25(OH)2D3 were significantly augmented along with a transient increase in urinary hydroxyproline excretion after Ca deprivation. These results suggest that serum BGP is increased after one week of Ca restriction in healthy subjects.

Adult↗
PubMed1991

Effects of arginine vasopressin on blood pressure and renal prostaglandin E2 in rabbits.

The role of arginine vasopressin (AVP) in blood pressure regulation in humans and animals is still controversial. The present study was designed to investigate the effects of AVP on blood pressure and the excretion of sodium and prostaglandin (PG) E2 in rabbits. AVP dissolved in 0.01 M acetic acid was infused subcutaneously at a rate of 0.86 ng/kg/min with a miniosmotic pump into 12 New Zealand white rabbits (2.7-3.4 kg), while 10 controls were given vehicle alone. AVP infusion resulted in a 3.5-fold rise in the level of plasma AVP (21.8 +/- 4.4 (SEM) pg/ml) as compared with controls, associated with a significant decrease in the urine volume and urinary excretion of sodium. The PGE2 excretion was increased 1.8-fold after AVP infusion. In the chronic AVP-infused group, blood pressure was not significantly increased, but the acute vascular response to AVP was significantly attenuated without any changes in the vasopressor response to angiotensin II. Preadministration of V1-antagonist completely abolished the vasopressor action of AVP, but not that of angiotensin II, in either group. These results suggest that circulating AVP within physiological range of concentrations may stimulate renal PGE2 synthesis and attenuate the vascular response through vascular V1 receptors without affecting the baroreflex, which may be attenuated through V2 receptors.

Angiotensin II↗
PubMed1991

Salmon calcitonin induces pituitary tumor in rats.

Calcitonin is widely used in the treatment of post-menopausal osteoporosis. The present study was designed to investigate the effects of salmon calcitonin (SCT) on the incidence of the pituitary tumors in Sprague-Dawley (SD) rats. Subcutaneous injections of SCT at a dose of 160 IU/kg/day for 6 months reduced body weight and induced one pituitary hyperplasia and three pituitary adenomas in 4 of 5 animals, while 5 controls did not show any changes. Prolactin-positive cells were located at the periphery of the affected pituitaries adjacent to the prolactin-negative adenomas. In addition, serum concentrations of prolactin and TSH were lower than in the controls, although serum calcium or LH levels were not significantly different from the controls. Among 7 animals treated with SCT for 6 months followed by no medication for another 6 months, 5 adenomas were detected, one of which had invasive growth toward the adjacent tissue, whereas only one adenoma was found in 9 controls. These results suggest that SCT administration at a high dose may induce the formation of pituitary adenoma, or may accelerate the development of spontaneous pituitary adenomas, some of which show frequent mitotic figures and invasive growth into the surrounding tissue, possibly resulting in malignant transformation. This indicates the need for caution in considering whether calcitonin injections into patients with osteoporosis as well as Paget's disease may induce such pituitary tumors.

Adenoma↗
PubMed1991

Effects of slow-release nifedipine on nighttime blood pressure.

With the advent of long-acting or slow-release antihypertensive drugs, we should be aware of a fall in nighttime blood pressure (BP) as well as daytime blood pressure. In the present study, casual BPs at the physician's office as well as ambulatory BP was recorded every hour throughout 24 hours with a noninvasive automated BP monitoring device in 24 essential hypertensives treated with slow-release nifedipine. Administration of slow-release nifedipine (20-40 mg, b.i.d.) decreased not only casual BPs but also ambulatory mean BP during the whole day or daytime (6 am to 10 pm). Slow-release nifedipine at 10 mg in the morning did not affect casual BPs at the office. However, mean BP obtained by ambulatory BP monitoring during the daytime was significantly attenuated. In addition, a profound fall in mean BP amounting to more than 20 mmHg during the night in some of the patients was observed during treatment with slow-release nifedipine not only at 20-40 mg (b.i.d.) but also at 10 mg once a day. These results suggest that we have to take into consideration the possibility that long-acting hypotensive agents may cause a great fall in nighttime BP during sleep, especially in the elderly.

Adult↗
PubMed1991

Clinical significance of ambulatory blood pressure monitoring. Evaluation of severity of hypertension, efficacy of treatment and effects on nighttime blood pressure.

Blood pressure (BP) obtained by the physician in his office and ambulatory BP recorded every hour throughout 24 hours with a noninvasive automated BP monitoring device were compared in 10 normotensives and 162 hypertensives. Casual BPs significantly correlated with averages in ambulatory BPs (ABPs) throughout the whole day, day (7 am - 10 pm) and night (0-5 am). However, it was noted that 6 of 10 normotensives and all of the moderate to severe hypertensives had ABPs of more than 150/90 mmHg at least once during the 24-hour period. The incidence of ABPs greater than 150/90 mmHg among all readings was higher in untreated and treated hypertensives with diastolic BPs in the office of more than 105 mmHg, and, when checked along with the clock time, higher not only in the morning but also in the evening. On the other hand, one-third or one-fifth of treated hypertensives with diastolic office BPs less than 90 mmHg or between 90 and 105 mmHg respectively had ABPs less than 150/90 mmHg throughout the whole day. When the effect of nicardipine (60 mg, t.i.d.) or slow-release nifedipine (27.3 +/- 3.0 mg, b.i.d.) on minimum BP during the night was analyzed, long-acting nifedipine decreased BP throughout the night to levels not significantly different from normotensive controls, whereas short-acting nicardipine did not affect nighttime BPs. These results suggest that simple ABP monitoring throughout the day gives us useful information to evaluate the severity of hypertension and the efficacy of antihypertensive medication as well as to avoid overtreatment with long-acting hypotensive agents resulting in a great fall in BP during sleep.

Blood Pressure Determination↗
PubMed1991

Blood ketone bodies in NIDDM: relationship with diabetic control and endogenous insulin secretion.

To evaluate the relationship of blood ketone bodies with diabetic control and endogenous insulin secretion, fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), fasting serum C-peptide (CPR), blood total ketone-bodies (TKB), blood acetoacetate (AcAc) and blood 3-hydroxybutyrate (3-OHB) were compared in 78 outpatients with non-insulin-dependent diabetes mellitus (NIDDM) treated with diet (n = 13), sulfonylurea (n = 52) and insulin (n = 13). TKB, AcAc and 3-OHB in patients treated with insulin were significantly higher than in patients treated with diet or sulfonylurea. In patients given diet therapy, log 3-OHB showed significant negative correlations with FPG, HbA1c and CPR. In patients treated with sulfonylurea, log 3-OHB showed significant positive correlations with FPG and HbA1c, but not with CPR. In patients treated with insulin, there were no correlations of log 3-OHB with FPG, HbA1c and CPR. For evaluation of the metabolic state in diabetes mellitus, measurement of blood ketone bodies is useful, and moreover necessary, in addition to diabetic control or determination of the endogenous insulin level.

3-Hydroxybutyric Acid↗
PubMed1991

Effects of PGE1 on the development of diabetes and surface markers of lymphocytes in BB/W/Tky rats.

To study the effect of an oral prostaglandin E1 (PGE1) derivative and/or lipo PGE1 on the onset of diabetes, these agents were administered to Bio-Breeding/Worcester/Tokyo (BB/W/Tky) rats from 4 to 13 weeks of age. Lymphocyte subsets in peripheral blood from normal Wistar and BB/W/Tky rats were measured before and for one week after administration of PGE1 using laser flow cytometry. Results showed that 14/16 (87.5%) of the BB/W/Tky rats administered PGE1 developed diabetes vs. 6/12 (50%) in the control BB/W/Tky rats. In normal Wistar rats, PGE1 significantly increased the W3/25+OX39+ and OX8+OX39+ cells. In BB/W/Tky rats, PGE1 significantly increased the OX19+OX6+, OX19+OX39+, W3/25+OX6+, W3/25+OX39+, OX8+, OX8+OX6+, OX8+OX39+ and OX39+ cells, while decreasing the OX6+ cells. We conclude that the administration of PGE1 to BB/W/Tky rats accelerates the development of spontaneous diabetes and alters the surface markers of lymphocytes.

Aging↗
PubMed1990

Hyperreninemia due to increased renal renin synthesis in BioBreeding Worcester rats.

It is well known that diabetes mellitus is often associated with hypertension. We previously reported the unresponsiveness of renin release to volume depletion with impaired renal prostaglandin E2 synthesis in rats with streptozotocin-induced diabetes. However, we have found that BioBreeding Worcester rats, spontaneously susceptible to diabetes mellitus either before or after the onset of diabetes, showed a pronounced fourfold to ninefold increase in plasma renin activity in comparison with control Wistar rats. Furthermore, these rats developed mild hypertension as high as 134 mm Hg after the age of 90 days. The hyperreninemia responded to 1-week sodium loading or restriction; the blood pressure increased during sodium loading. Oral administration of captopril (30 mg/kg) for 1 week resulted in a large blood pressure decrease (-47.1 +/- 5.9 mm Hg, n = 10) in comparison with controls (-17.0 +/- 4.7 mm Hg, n = 12). Vascular response to angiotensin II was also attenuated. Plasma angiotensin II levels were 5.7-fold higher and associated with a 1.5-fold increase of plasma aldosterone concentration compared with control rats, whereas angiotensinogen-plasma concentrations were lower than in control rats. The renal renin content determined enzymatically or histochemically was more enhanced in BioBreeding Worcester rats than in control rats, but the renal renin messenger RNA levels did not differ. These results suggest that the strain-specific hyperreninemia in BioBreeding Worcester rats might be due to posttranscriptional abnormalities of renal renin synthesis. Further work is needed to elucidate the specific mechanism or mechanisms responsible.

Angiotensin II↗
PubMed1990

Effect of captopril on glucose concentration. Possible role of augmented postprandial forearm blood flow.

The goal of this study was to evaluate the effects of captopril on plasma glucose concentration. The daily profiles of the plasma glucose levels were determined in 12 non-insulin-dependent diabetic normotensive subjects, treated with or without captopril at a dose of 25 mg 3 times/day. Forearm blood flow was also measured by strain-gauge plethysmography. Administration of captopril improved the daily profile of the plasma glucose level. Postprandial forearm blood flow was also augmented 2 h after a meal. These results suggest that angiotensin-converting enzyme inhibitors may improve glucose metabolism in diabetic subjects, possibly through enhancement of blood flow to skeletal muscle.

Blood Glucose↗
PubMed1989

Effect of captopril or enalapril on renal prostaglandin E2.

Since one of the hypotensive mechanisms of angiotensin-converting enzyme inhibitor (ACEI) has been suggested to be mediated through the renal kinin-prostaglandin (PG) axis, the present study was designed to investigate the effect of captopril (C) or enalapril (E) on renal PGE2 excretion or synthesis. Wistar male rats (BW 200-250 g) were given orally captopril at 30 mg/kg/day or enalapril at 10 or 30 mg/kg for one week. Before and after ACEI, blood pressure (tail cuff method) as well as PRA and urinary PGE2 excretion was determined. Renopapillary slices were obtained from some of the rats including controls and incubated to determine PGE2 synthesis. C or E administration resulted in a blood pressure decrease of 21 to 36 mm Hg with an increase in PRA. Urine volume and sodium excretion increased after daily treatment with C or E at 30 mg/kg. Urinary PGE2 excretion increased 1.4-fold in response to C, but not to E. Papillary PGE2 synthesis demonstrated a marked decrease 2 h after in vivo administration of either ACEI compared to controls. However, when C or enalaprilat was added in vitro to renal slices obtained from controls, only C at 10(-5) M showed a significant 2-fold increase in renal PGE2 synthesis. These results suggest that (1) renal PGE2 synthesis may be dependent on circulating angiotensin II. (2) C, but not enalaprilat, has a direct stimulatory effect on renal PGE2 synthesis and (3) renal PGE2 may not be involved very much in the hypotensive effect of ACEI.

Animals↗
PubMed1989

Reversible hyporeninemic hypoaldosteronism in a patient with tetraplegia.

A 66-year-old man with tetraplegia developed hyperkalemia. Hyporeninemic hypoaldosteronism was disclosed on the basis of a lack of response of plasma renin activity to furosemide administration or tilting with marked hypotension and a subnormal response of aldosterone to furosemide stimulation, tilting, angiotensin II infusion and ACTH administration, as well as increased vascular responsiveness to angiotensin II infusion. Of interest was the finding that urinary excretion of epinephrine and norepinephrine was markedly reduced, indicating that hyporeninemia may possibly be due to a chronic lack of sympathetic nervous stimuli. The patient was treated with sodium polystyrene sulfonate resin and/or 9-alpha-fluorohydrocortisone, and wheelchair rehabilitation. However, even after stopping 8-month-mineralcorticoid replacement, normokalemia was maintained. Reexamination of the renin-angiotensin-aldosterone system revealed a normalized response to tilting or ACTH administration along with the normal catecholamine excretion. One more point to be noted is that ACTH administration resulted in a rise in the plasma levels of cortisol, corticosterone and 18-OH-corticosterone, but not aldosterone. This may be attributed to ACTH-stimulated 18-OH-corticosterone derived from the zona fasciculata or alternatively to a partial defect of corticosterone methyl oxidase type II (18-dehydrogenase) in the adrenal glomerulosa cells. These results suggested that hyporeninemic hypoaldosteronism may have been attributable to a decrease in systemic nervous stimuli and that such abnormalities were reversible.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

High glucose concentration suppresses mesangial laminin B2 gene expression.

To study the role of laminin in the rat mesangial cell attachment, cell adhesion to laminin-coated dishes was assayed by adding various amounts of a pentapeptide (YIGSR). YIGSR (20-100 micrograms/mL) inhibited the cell attachment to laminin-coated dishes. Mesangial laminin B2 messenger RNA (mRNA) levels were attenuated during exposure to 30 mM glucose or high osmolarity achieved by the addition of 25 mM choline chloride to 5 mM glucose (310 mOsm/kg H2O) for 3 hours. These results suggest that laminin, which may have a physiologic role in mesangial cell attachment, is produced in mesangial cells, and that the decrease of laminin B2 mRNA during hyperglycemia or exposure to high osmolarity may have some pathophysiologic significance in the development of diabetic nephropathy.

Amino Acid Sequence↗