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PubMed1968

Elevated serum human growth hormone and decreased serum insulin in prediabetic males after intravenous tolbutamide and glucose.

Serum human growth hormone (HGH), serum immunoreactive insulin (IRI), plasma free fatty acids, and blood glucose were measured during intravenous glucose and intravenous tolbutamide tolerance tests in 13 normal and 13 prediabetic (offspring of two diabetic parents) males, closely matched for weight and age. Only prediabetics with normal glucose tolerance during oral, intravenous, and cortisone-primed glucose tolerance tests were evaluated. Mean serum HGH levels were significantly higher in prediabetics in response to intravenous tolbutamide and at the end of the 3-hr intravenous glucose tolerance tests (IVGTT). This is interpreted as a hyperresponsiveness of the growth hormone-releasing mechanisms in prediabetic subjects. The insulin response during the first 10 min of an IVGTT was significantly reduced in prediabetic males as compared to normal controls, whereas the insulin response to intravenous tolbutamide was not significantly different at the same time intervals in the same subjects.It appears, therefore, that measuring IRI during an IVGTT can be valuable in detecting the earliest signs of diabetes even before any disturbance of blood glucose homeostasis is seen. The possibility that growth hormone hypersecretion in prediabetics might play a role in the pathogenesis of human diabetes mellitus is discussed.

Adult↗
PubMedDate not supplied

The effect of a very low dose of tolbutamide combined with an alpha-glucosidase inhibitor in non-insulin-dependent diabetes mellitus.

The effect of adding a very low dose of a sulphonylurea (tolbutamide) to the treatment of 10 patients with noninsulin-dependent diabetes mellitus (NIDDM) was investigated. Patients took 0.1 mg tds of an alpha-glucosidase inhibitor orally for 8 weeks, and 50 mg tds of the sulphonylurea, tolbutamide, for the last 4 weeks of this period. The glycosylated haemoglobin level was significantly reduced during the combined treatment period compared with the level after treatment with alpha-glucosidase inhibitor alone (P = 0.035), although not compared with the pretreatment level. There were no significant changes in post-prandial blood glucose, serum lipid levels or connective peptide immunoreactivities. These preliminary results indicate that the addition of a very low dose of tolbutamide to a recommended diet and treatment with an alpha-glucosidase inhibitor, may improve glucose metabolism without raising insulin secretion or influencing lipid metabolism.

Aged↗
PubMed1986

Quantitative morphometric studies of pancreatic islets obtained from tolbutamide-treated rats.

We have developed a computerized system for quantitative morphometric analysis of the number and position of secretory granules and organelles in pancreatic islet beta cells following tolbutamide treatment. Data from animals injected with tolbutamide for 1, 2, and 3 days were compared to tissues obtained from untreated control animals. Pancreatic islets removed by a collagenase technique were perfused with an appropriate medium to restore a basal state. After fixation and embedding, thick sections of beta cells were viewed by electron microscopy. Morphometric studies of randomly selected or serially cut cells were performed with computer programs for digitization, quantify, rotational, and perspective display. Tolbutamide treatment resulted in graded granule depletion which was maximal at 72 hr relative to control animals. Reduced granule density was associated with significant reduction in total cell area or cytoplasmic area, but was without effect on nuclear size. Since granule depletion improved visualization of subcellular structures, this will enable us to pursue studies of exocytosis under a variety of physiological conditions.

Animals↗
PubMed1982

Stimulatory effects of tolbutamide infusion on plasma glucagon in insulin-dependent diabetic subjects.

The effect of iv tolbutamide on endogenous glucagon levels was measured in nine insulin-dependent diabetic patients chosen because they evidenced no C-peptide response to beta-cell secretagogues. Basal glucagon levels were not suppressed by a sustained tolbutamide infusion; in fact, a slight stimulatory effect was observed at 5, 10, 30, and 45 min. In the absence of detectable insulin secretory capacity and suboptimal insulin replacement, tolbutamide appears to be a stimulus, not a suppressant, of glucagon secretion.

Adult↗
PubMed1985

Effects of salicylate, tolbutamide, and prostaglandin E2 on insulin responses to glucose in noninsulin-dependent diabetes mellitus.

To assess whether the beneficial effects of salicylates compounds and sulfonylureas on insulin secretion in patients with noninsulin-dependent diabetes mellitus could be ascribed to inhibition of prostaglandin E (PGE) synthesis, insulin responses to iv glucose pulses were determined in diabetic patients during infusion of lysine acetylsalicylate (LAS) or tolbutamide, with or without a concurrent infusion of PGE2. In these diabetic patients, the augmenting effects of LAS on glucose-induced insulin secretion were abolished by PGE2 infusion. Partial restoration by tolbutamide infusion of the first and second phases of glucose-induced insulin secretion was not affected by the administration of PGE2. The stimulatory effects of LAS and tolbutamide on insulin secretion were additive, suggesting separate mechanisms of action. Since salicylates and sulfonylureas lower plasma glucose concentrations, we also evaluated whether prevention of the fall in the prestimulus glucose level could result in a further amplification of insulin release. Resetting the prestimulus glucose level to control values by infusing glucose caused a further increase in the second, but not the first, phase of glucose-induced insulin secretion, indicating that the prestimulus glucose level had a role in regulating subsequent insulin release. These results indicate that salicylates, but not sulfonylureas, exert their acute insulinotropic effect in noninsulin-dependent diabetic patients by inhibiting endogenous PGE synthesis and support the idea that endogenous PGE may play a role in the impaired insulin response to glucose in this form of human diabetes.

Adult↗
PubMed1981

Plasma insulin, C-peptide, and blood glucose in portal, hepatic and peripheral veins in liver cirrhosis. Effect of intravenous tolbutamide.

The responses of portal, hepatic and peripheral venous blood glucose (BG), plasma insulin (IRI) and C-peptide (IRC) levels to iv tolbutamide (200 mg) have been determined in 9 non-diabetic patients with liver cirrhosis and in 6 control subjects. The basal levels of plasma IRI and IRC were similar in patients and controls as were the portal and peripheral BG levels. In the hepatic vein, however, the BG-levels were higher in cirrhotic patients than in controls. After tolbutamide administration the BG-levels were unchanged in the cirrhotic patients but a significant fall in hepatic vein BG was observed in controls. In both groups of subjects the highest post-tolbutamide IRI-levels were found in the portal vein whereas the corresponding IRC-levels were as high in the hepatic as in the portal vein. The increments of portal venous IRI and IRC were significantly higher in controls as compared to the cirrhotic patients. Nevertheless, in the peripheral veins the increments of IRI and IRC were very similar in both groups of subjects or even less in the control subjects. The results suggest that in patient with liver cirrhosis the secretion of insulin is not increased but slightly decreased. The production of glucose by the liver also seems to be increased either due to insulin resistance or portal venous shunting of insulin.

Adult↗
PubMed1988

Opposing effects of glucose and tolbutamide on the sodium content of rat pancreatic islets.

Integrating flame photometry was employed for measuring sodium in rat pancreatic islets incubated in media buffered with HEPES or bicarbonate. The sodium content decreased by nearly 40% when the islets were exposed to 5 mmol/l glucose, no further reduction being seen with additional rise of the concentration to 20 mmol/l. Whereas the depressing effect of glucose was mimicked by 100 mumol/l quinine, increased sodium contents were noted after inhibition of the Na/K pump (removal of extracellular K+ or addition of 1 mmol/l ouabain) or exposure of the islets to 1 mmol/l tolbutamide. Although promoting sodium accumulation in the islet cells, tolbutamide counteracted the increase in sodium obtained on withdrawal of K+ from the incubation medium. It is suggested that tolbutamide in addition to its major effect in promoting the entry of Ca2+ also facilitates insulin release by suppressing the outward transport of this ion.

Animals↗
PubMed1976

Cyclic nucleotides in pancreatic islets. Tolbutamide- and arginine-induced insulin release.

With the use of isolated rat islet perfusion, levels of the islet cyclic adenosine 3' ,5' -monophosphate (cAMP) were compared with dynamic insulin secretion induced by tolbutamide and arginine. Tolbutamide elevated islet cAMP rapidly and augmented both glucose-induced islet cAMP levels and insulin secretion; arginine, however, did not elevate islet cAMP but did enhance glucose-induced insulin secretion. Since the latter result could have been modulated by cyclic guanosine 3' ,5' -monophosphate, this cyclic nucleotide was also measured and found to remain unchanged during stimulation of insulin secretion by arginine and a combination or arginine and glucose. Thus, the action of tolbutamide appears to be modulated in part by cAMP, whereas arginine appears to augment insulin secretion independently of cyclic nucleotides.

Animals↗
PubMed1977

Tolbutamide-induced hemolytic anemia.

A 67-year-old female diabetic is presented who developed a Coombs'-positive hemolytic anemia after a year of treatment with tolbutamide. An IgG antibody was identified in the patient's serum that caused the agglutination of both the patient's red blood cells and tolbutamide-coated erythrocytes in the absence of complement. Such a reaction did not occur with the patient's erythrocytes when not exposed to tolbutamide. Agglutination of the patient's serum also occurred with erythrocytes treated with other sulfonylureas (chlorpropamide, glibenclamide, carbutamide) but not with phenacetin.

Aged↗
PubMed1997

Parallel reduction of pancreas insulin content and insulin secretion in 48-h tolbutamide-infused normoglycemic rats.

The overworked-beta-cell hypothesis proposes that lowered glucose-potentiated insulin secretory responses in diabetes are secondary to hyperstimulated insulin secretion and depletion of the beta-cell insulin stores. We tested this hypothesis in normal rats using a 48-h infusion of 200 mg x kg(-1) x day(-1) tolbutamide in 20% glucose. Insulin secretion was measured by in vitro pancreas perfusion. Twice daily blood glucose values were equal in the tolbutamide-infused and control rats. Pancreas insulin content was 47 +/- 7% that of the controls (P < 0.004). Insulin responses to 16.7 mmol/l glucose, 16.7 mmol/l glucose/10 mmol/l arginine, and 5.5 mmol/l glucose/10 mmol/l arginine were reduced in parallel, except for the first phase response to 16.7 mmol/l glucose/arginine. Pancreas amylin content was unchanged in the tolbutamide-infused rats as was amylin secretion, resulting in higher than normal stored and secreted amylin-to-insulin molar ratios. Importantly, a raised amylin-to-insulin ratio and a relatively unimpaired first versus second phase insulin response for high glucose/arginine both occur in diabetic rats. Thus, our results support the overworked-beta-cell hypothesis by showing chronic beta-cell stimulation without hyperglycemia replicates part of the beta-cell dysfunction found with diabetes.

Amyloid↗
PubMed1998

Decreased tolbutamide-stimulated insulin secretion in healthy subjects with sequence variants in the high-affinity sulfonylurea receptor gene.

The high-affinity sulfonylurea receptor (SUR1) is, as a subunit of the ATP-sensitive potassium channel, an important regulator of insulin secretion in the pancreatic beta-cell. The aim of this study was to examine if genetic variability of the SUR1 gene was associated with NIDDM or altered pancreatic beta-cell function. Mutational analysis of all the 39 SUR1 exons, including intron-exon boundaries, in 63 NIDDM patients revealed two missense variants, five silent variants in the coding region, and four intron variants. The two missense variants (Asp673Asn and Ser1369Ala) and two sequence variants (ACC-->ACT, Thr759Thr and a c-->t intron variant in position -3 of the exon 16 splice acceptor site) were examined for association with NIDDM and for a possible influence on insulin and C-peptide secretion after intravenous glucose and tolbutamide loads in a random sample of unrelated, healthy, young Danish Caucasians. The Asp673Asn variant in exon 14 was only identified in one NIDDM patient, and the allelic frequency of the Ser1369Ala was similar among 247 control subjects (0.38 [95% CI 0.34-0.42]) and 406 NIDDM patients (0.40 [0.37-0.43]). The allelic frequency of the silent exon 18 Thr775Thr variant was 0.051 (0.035-0.067) in NIDDM patients (n=392) and 0.027 (0.013-0.041) in control subjects (n=246; chi2=4.99, P=0.03). The allelic frequency of the intron variant was similar among NIDDM patients (0.45 [0.42-0.48]) and control subjects (0.44 [0.40-0.48]). Of 386 NIDDM patients, 17 had the combined genotype exon 18 C/T and intron -3c/-3t (0.044 [0.024-0.064]), whereas 3 of 243 control subjects had the same combined genotype (0.012 [0-0.026]; chi2=4.87, P=0.03; odds ratio: 3.69 [1.07-12.71]). Of 380 unrelated, healthy, young Danish Caucasians, 10 (0.026 [0.010-0.042]) had the combined at-risk genotype. These subjects had, on average, a 50% reduction in serum C-peptide and a 40% reduction in serum insulin responses upon tolbutamide injection (P=0.002 and P=0.05, respectively) but normal serum C-peptide and insulin responses upon glucose injection. In conclusion, a silent polymorphism in exon 18 of the SUR1 gene is associated with NIDDM in a Danish Caucasian population. In combination with an intron variant, the association is higher, and young, healthy carriers of the intragenic combination have reduced serum C-peptide and insulin responses to a tolbutamide load.

ATP-Binding Cassette Transporters↗
PubMed1999

Different effects of tolbutamide and diazoxide in alpha, beta-, and delta-cells within intact islets of Langerhans.

Interaction between the different types of cells within the islet of Langerhans is vital for adequate control of insulin release. Once insulin secretion becomes defective, as in type 2 diabetes, the most useful drugs to increase insulin release are sulfonylureas. It is well-known that sulfonylureas block K(ATP) channels, which results in depolarization of the membrane that provokes calcium influx and increases intracellular calcium concentration ([Ca2+]i), which thereby triggers insulin secretion. The sulfonamide diazoxide produces the opposite effect: it activates K(ATP) channels, resulting in a decreased insulin secretion. Despite such evidence, little is known about the effect of sulfonylureas and sulfonamides in non-beta-cells of the islet of Langerhans. In this article, we describe the effects of tolbutamide and diazoxide on [Ca2+]i in alpha-, beta-, and delta-cells within intact islets of Langerhans. Tolbutamide elicits an increase in [Ca2+li in beta- and delta-cells, regardless of glucose concentrations. Remarkably, tolbutamide is without effect in alpha-cells. When diazoxide is applied, glucose-induced [Ca2+]i oscillations in beta- and delta-cells are abolished, whereas [Ca2+]i oscillations in alpha-cells remain unaltered. Furthermore, the existence of sulfonylurea receptors is demonstrated in beta-cells but not in alpha-cells by using binding of glybenclamide-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) combined with immunostaining for insulin and glucagon.

Animals↗
PubMed1984

Circannual rhythm of insulin release and hypoglycemic effect of tolbutamide stimulus in healthy man.

Four healthy non obese young volunteers were observed for a 24-hr period, every other month, over the course of one year. Tolbutamide was injected i.v. each day of the experiment every four hours. Tolbutamide-induced insulin secretion (T.I.I.S.) was evaluated by planimetrically measuring insulin areas above basal levels. Tolbutamide-induced hypoglycemic effect was evaluated by measuring the blood glucose difference between the 5th and 25th minute after the drug injection (delta G5'-25'). The macroscopic evaluation of T.I.I.S. and delta G5'-25' (mean chronograms) permitted the detection of the existence of a circannual variation of both variables. In particular the maximum level of the blood glucose drop (delta G5'-25') was registered in February. Subsequently the quantification of the rhythm of T.I.I.S. was obtained by fitting a sine curve, according to the Cosinor method. The highest insulin release was confirmed in winter. As previously documented, the existence of a statistically significant circadian rhythm of T.I.I.S. was confirmed in the morning, i.e. the same period of the day in which insulin-induced hypoglycemia occurs.

Adult↗
PubMed1975

Responses to intravenous tolbutamide by Nigerians--a preliminary study.

Sixteen normal adult Nigerians (10 males and 6 females) were randomly selected for an intravenous tolbutamide test. The mean fall of blood sugar at 30 minutes corresponded closely to values observed in the Caucasians; however, there was a delay in the return of blood sugar to fasting level even at 240 minutes following tolbutamide administration. In spite of the low individual blood sugar levels attained during the study, no associated symptoms were observed. The possible contributory role of the counter-regulatory mechanisms in explaining the differences in the response to tolbutamide between the Nigerian and the Caucasian is discussed.

Adult↗
PubMed1975

Acute suppressive effect of human growth hormone on insulin release induced by glucagon and tolbutamide in man.

The acute effect of human growth hormone on glucagon--and tolbutamide--induced insulin release was investigated in 14 non-obese subjects with normal glucose tolerance. Sixty mn after an i.v. growth hormone infusion of 40 mug/kg per kg body weight, the insulin response to glucagon (10 subjects) as well as to tolbutamide (6 subjects) was significantly suppressed by about 35%, both if the insulin secretion was expressed as change in peak response (p less than 0.05 for both insulinogogues) or as per cent change of the integrated insulin area over 30 minutes (p less than 0.005 and p less than 0.05, respectively). A lesser reduction of glucagon-induced insulin secretion was observed also after smaller doses of growth hormone (10 and 20 mug/kg). The reduction of the insulin response was associated with a significantly smaller blood glucose fall following the glucagon and tolbutamide administration. These results support the hypothesis that growth hormone in vivo has an acute suppressive effect on insulin secretion, and show that this action is not limited to glucose-induced stimulation of the islets.

Acromegaly↗
PubMedDate not supplied

[Relative effectiveness of tolbutamide, chlorpropamide and gliclazide].

In clinical practice of hypoglycemic therapy of diabetes mellitus the problem of the optimal selection of oral hypoglycemic agent, corresponding to the individual patterns of regulatory and metabolic disturbances is of primary importance. The individual, pathophysiological basis should be met as much as possible by the pharmacodynamic properties of the selected, hypoglycemic drug. For this reason group of 23 diabetics type II underwent a prolonged, open trial of controlled pharmacotherapy with 4 sulphonylurea derivatives. Pertinent clinical and metabolic parameters were assessed before, during and after planned periods of therapy with Tolbutamide or Chlorpropamide to Gliclazide and Gliclazide to Glibenclamide. In the same time the levels of serum insulin fasting and after breakfast were determined. Also the comparative efficacy of the exchange of the drug in a subgroup of diabetics with fasting glycemia below and above 160 mg% was assessed. It was shown, that the change of Tolbutamide or Chlorpropamide to Gliclazide or Glibenclamide improved the therapeutical effectiveness in general. The individual responses to such a change were however individually differentiated. The change of Tolbutamide or Chlorpropamide to Gliclazide increased the therapeutical efficacy only in these patients, in whom such a change was associated with an increase of prandial, reactive serum insulin level (IRI). In practice they were patients with the fasting glycemia lower than 160 mg%. In patients with fasting glycemia higher than 160 mg% the change of oral compounds under study was not connected with an increase of prandial serum insulin. The metabolic parameters have not improved either. Perhaps they were patients with diabetes mellitus type II, who should be primarily qualified to insulin.

Administration, Oral↗
PubMed1991

[Enhancement of potential-dependent inactivation of calcium channels of mollusk neurons by tolbutamide].

A two-microelectrode voltage-clamp method was used to measure a potential-dependent Ca-current (ICa) on isolated snail neurons. Tolbutamide (1-5 mmol/l) and H-8 (1-30 mumol/l), inhibitors of kinase A, caused a decrease in the peak amplitude and an acceleration of the ICa decay during a depolarizing step. In the presence of tolbutamide a slow (tau 2) time constant of the ICa decay has grown 2-3 times stronger than fast (tau 1) time constant. Curves of inactivation obtained in double-pulse experiments have shown that after tolbutamide application an inactivation of the ICa enhanced when prepulses were to +30(-)+70 mV. The results suggest that dephosphorylation of Ca(2+)-channels enhances a potential-dependent component of the ICa inactivation.

Animals↗
PubMed1991

Studies on 8-methoxypsoralen tolbutamide interactions. 2. Studies after U.V.-A irradiation in vitro and in vivo.

Previous studies had evidenced that tolbutamide has influence on the complex formation between 8-methoxypsoralen (8-MOP) and serum albumin, both in vitro and in vivo, partially displacing it from its binding site. We have now extended this research by studying competition under UV-A irradiation, thus approaching the conditions which occur during PUVA therapy more closely. Research was first carried out in vitro, studying tolbutamide competing with bound 8-MOP in human serum after irradiation with UV-A. From the data obtained, it appears that the displacement is not influenced to any significant extent by irradiation. Experiments were then carried out in vivo on mice treated with the two drugs and irradiated with UV-A in conditions analogous to those generally used for PUVA therapy; the amount of 8-MOP localized in blood serum and in various organs was then determined. Concerning distribution of 8-MOP, results confirmed what had been previously obtained; concerning irradiation, results showed that the effect on the 8-MOP displacement by tolbutamide was not statistically significative in the most organs considered. A slight difference in respect to the results obtained without irradiation was observed only in the cases of skin, eyes and ears.

Adult↗