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The effect of exogenous acid amyloglucosidase on sulphonylurea-induced insulin release was investigated in mice and rats. 1. Pretreatment of mice with acid amyloglucosidase enhanced insulin release induced by the different sulphonylurea derivatives, carbutamide, tolbutamide, glibenclamide, and glibornuride. 2. A dose-response relationship between glibenclamide-induced insulin response and amyloglucosidase dosage covering a 64-fold concentration range was established in mice. 3. Pretreatment of the animals with other macromolecules of similar physiological or chemical properties to acid amyloglucosidase such asα-amylase,β-glucuronidase and albumin did not influence glibenlamide-induced insulin release. 4. The effect of acid amyloglucosidase pretreatment on insulin release induced by different agents known to affect the islet-cell adenylate cyclase-cyclic AMP system such as secretin, L-isopropylnoradrenaline (L-IPNA), arginine, glibenclamide and 3-isobutyl-1-methylxanthine (IBMX) was tested. It was observed that in animals pretreated with acid amyloglucosidase, insulin release was enhanced when stimulated by glibenclamide, a phosphodiesterase inhibitor, but it was similarly enhanced by arginine, a phosphodiesterase activator. Insulin release induced by secretin, L-IPNA, and IBMX was unaffected. 5. Acid amyloglucosidase pretreatment in rats enhanced plasma immunoreactive insulin levels following glibenclamide injection not only in the peripheral veins but also in the portal vein. 6. Mice fasted for 24 hrs displayed a markedly depressed insulin response to tolbutamide injection. Pretreatment of the fasted animals with acid amyloglucosidase could restore the tolbutamide-induced insulin release to the same level as that recorded in a group of freely fed mice. It is suggested that acid amyloglucosidase plays an important role in insulin secretion induced by sulphonylureas. Most evidence suggests that this effect is exerted within the B-cell although an additional effect on the liver cannot be ruled out.

Pharmacodynamic studies were performed using tolbutamide, glibenclamide, glibornuride (Ro 6-4563) and glisoxepide (BS 4231). The four compounds were administered intravenously, and exact dose-response relations were established, calculating the ED 30 of the decrease in blood glucose in healthy volunteers. Accordingly, the dose corresponding to the ED 30 was given twice with a three hour interval to maturity-onset diabetics. Different dynamics of insulin response were observed after tolbutamide, glibornuride and glisoxepide on the one hand, and glibenclamide on the other. In contrast to other reports in the literature, an obvious uniformly weaker degree of insulin secretion was seen after each of the different sulphonylurea compounds when given repeatedly.

The uptake of 3H-labelled glibomuride wasstudied in microdissected pancreatic islets of ob/ob- mice . The islets rapidly accumulated this insulin-releasi

Glibornuride is an addition to the second-generation sulphonylureas, that has been shown in clinical trials to be effective and non-toxic. Twenty-three diabetics who were poorly controlled on other oral hypoglycaemic agents and seven newly diagnosed diabetics were treated with glibornuride. The efficacy and lack of toxicity of this drug was confirmed, but there was no evidence to suggest that it is significantly more potent than other sulphonylureas. It does not seem to represent a significant therapeutic advance.

1. Anhand des Sekretionsverhaltens von Insulin ist Ro 6-4563, ein neues Sulfonylharnstoffderivat, in die Reihe der „tolbutamidartig wirkenden Sulfonylharnstoffderivate“ einzuordnen. 2. Die intravenose Gabe von 25 mg R 6-4563 fuhrt im Vergleich zur intravenosen Gabe von 1000 mg Tolbutamid zu teilweise geringfugig hoheren Seruminsulinspiegeln. Die Glucose- und NFS-Werte im Serum sind unter beiden Praparaten jedoch nahezu identisch, so das 25 mg Ro 6-4563 und 1000 mg Tolbutamid als annahernd gleichwertig zu bezeichnen sind.