A new benzothiadiazine derivative, LN 5330: effects on pancreatic hormones

Abstract

Summary. LN 5330 is a new benzothiadiazine which is a structural analogue of diazoxide. Its effects in vivo were studied on blood glucose levels and insulin, glucagon and somatostatin secretion in normal dogs, and in vitro on glucagon and insulin secretion from the isolated perfused rat pancreas. The results were compared with those obtained with diazoxide at equimolar dose or concentration. In the normal anaesthetized dog having a T-shaped catheter inserted in the pancreaticoduodenal vein, the infusion of LN 5330 (87.8 lxmol/kg for 20 rain) induced (1) a progressive increase in blood glucose levels, (2) a rapid decrease in insulin and somatostatin output rate, (3) an immediate increase in pancreatic glucagon secretion, and (4) a delayed decrease of arterial blood pressure. The equimolar dose of diazoxide provoked the same effects on blood glucose levels, insulin and somatostatin output, but a marked decrease in glucagon output and in arterial blood pressure. In the isolated rat pancreas perfused with 8.3 retool/1 glucose, the infusion of LN 5330 (440 p.mol/1 for 30 rain) induced a drastic fall in insulin and a rapid and persistent increase in glucagon output. This stimulatory effect on glucagon secretion was not found with diazoxide at equimolar concentration. These findings show that LN 5330 is a substance which is distinct from diazoxide and interesting because of its double action: inhibition of insulin secretion and stimulation of glucagon secretion.Key words: Benzothiadiazine analogue, LN 5330, diazoxide, glucagon, insulin, somatostatin secretion, dog, isolated perfused rat pancreas.Chloro-7 trifluoromethyl-6 benzothiadiazine-a,2,4 dioxide-l,1 (LN5330) is a new benzothiadiazine (Fig.l) which is a structural analogue of diazoxide, a known inhibitor of insulin secretion. We have shown previously that LN 5330, like diazoxide, strongly inhibits insulin secretion from the isolated perfused pancreas of the rat. However, after ceasing the LN 5330 infusion, we observed a marked increase in insulin output, which was not found with diazoxide [1].The aim of the present study was to investigate the effects of LN 5330 on pancreatic hormones in the dog in vivo and to compare them with those obtained with diazoxide. Since these revealed that LN 5330 and diazoxide had different effects on glucagon secretion, we investigated whether this difference could be found also in the isolated perfused rat pancreas.Cl %7 ~ Materials and methods AnimalsStudies were carried out either in vivo in normal dogs or in vitro on isolated perfused rat pancreas. Experiments in vivoNormal mongrel dogs were used, weighing 15-20kg. Before experiments, the animals had free access to water and a standard balanced diet (UAR121, Villemoisson-sur-Orge, France). They were fasted for 18 h before the experiment. The animals were anaesthetized intravenously with pentobarbital (30mg/kg body weight). After a median laparotomy, a T-shaped catheter was inserted into the pancreaticoduodenal vein. The animals were given heparin intravenously (5 mg/kg). Venous ...

Dietary and pharmacological modification of the insulin/IGF-1 system: exploiting the full repertoire against cancer

“…192 In moderately overweight patients with polycystic ovary syndrome, 300 mg diazoxide per day also reduced IGF-1 from 314.5 to 219.5 ng/ml ( P <0.01). 193 Furthermore, diazoxide inhibits glucagon secretion in healthy man 194 and in the dog, 195 but stimulates glucagon release in rats. 196 …”

ATP-sensitive potassium channel (KATPchannel) expression in the normal canine pancreas and in canine insulinomas

“…The mechanisms of sulfonyluea and diazoxide on the pancreatic beta cell have not been studied at the molecular level in the dog but the results of this study predict that these pharmacologic agents will act via the K ATP channel to alter insulin secretion. Indeed, in vivo studies have shown the expected changes in serum insulin and glucose levels in dogs treated with sulfonylureas or diazoxide [ 10 - 13 ].…”

“…Although sulfonylurea drugs and diazoxide have the expected effects on insulin secretion from normal dogs [ 10 - 13 ], little information is known about the canine beta cell K ATP channel that is the molecular target for these drugs. Some but not all canine insulinomas respond to diazoxide [ 14 ], suggesting the possibility that mutations in the K ATP channel could be responsible for drug failure in some cases.…”