Effects of ruminal infusion of volatile fatty acids on plasma concentration of growth hormone and insulin in sheep

In an initial experiment we observed postprandial changes in plasma concentrations of growth hormone (GH), insulin, glucagon, and somatostatin (SRIF) in sheep. We then examined whether increasing the rumen concentration of volatile fatty acids (VFA) by infusing a VFA mixture at three rates (53.5, 107, and 214 micromol/kg/min for 4 hr) mimicked the postprandial changes in hormone secretion. Feeding significantly (P < 0.05) suppressed the plasma GH concentration for 6 hr, whereas it significantly (P < 0.05) increased plasma concentrations of insulin, glucagon, and SRIF. Plasma glucose levels tended to decrease after feeding but then gradually increased over the prefeeding level (P < 0.05). Intraruminal infusion of the VFA mixture at 107 micromol/kg/min caused similar changes in ruminal VFA concentrations to those seen after feeding. The infusion significantly (P < 0.05) suppressed GH secretion in a dose-dependent manner, whereas it caused a significant (P < 0.05) increase in insulin and glucose concentrations without changing glucagon concentrations. From these results, we conclude that the postprandial change in ruminal VFA concentration may be a physiological signal which modifies GH and insulin secretion in sheep.

Plasma glicentin in diabetic and gastrectomized patients

Recent successful synthesis of human glicentin prompted us to establish an immunoassay method for determination of human glicentin in plasma. Human glicentin in plasma was measured using a newly developed sandwich ELISA. The mean fasting levels of human glicentin were 18.6+/-2.4 and 19.7+/-2.1 pM in normal subjects and diabetic patients, respectively. In diabetic patients with renal failure, plasma glicentin was elevated, exceeding 100 pM. In normal subjects, plasma glicentin increased to a peak level of about 130 pM at 60 min after an oral glucose load, and then decreased. In patients who underwent gastrectomy, plasma glicentin rapidly increased to a peak of about 300 pM at 30 min after oral glucose load. In a patient with short bowel syndrome plasma glicentin did not change following an oral glucose load. These results correspond with previous findings for gut glucagon-like immunoreactive materials (GLI) or enteroglucagon. We conclude that glicentin is secreted from the small intestine in response to intraluminal glucose stimulation in humans.

Inhibition of GH releasing factor (GRF)-induced GH secretion by intraruminal infusion of volatile fatty acids (VFA) in sheep

A VFA mixture solution containing acetate, propionate and butyrate (the molar ratio of acetate, propionate and n-butyrate = 61.7:24.3:14.0) was infused into the rumen at various rates (53.5, 107 and 214 mumol kg-1 min-1) over 6 h to examine the effects on basal and growth hormone-releasing factor (GRF, 0.25 micrograms kg-1)-induced increase in secretion of GH, insulin, glucagon and somatostatin (SRIF) in five castrated male sheep. Intraruminal infusion of the VFA mixture into the 18-h-fasted animals at the rates of 53.5, 107 and 214 mumol kg-1 min-1 finally raised the total intraruminal VFA concentration from 91.4 to 100.2 (P > 0.05), 175.9 (P < 0.05) and 234.5 (P < 0.05) mmol l-1, respectively. A preliminary experiment showed that an infusion rate of 107 mumol kg-1 min-1 mimics the postprandial increase in ruminal VFA. The basal plasma GH concentrations (2 to 4 h after the start of VFA infusion) and the area under the profiles for GH release in response to the intravenous GRF injection, which was done 4 h after the start of VFA infusion, were significantly decreased by the VFA infusion rates of 107 and 214 mumol kg-1 min-1. Furthermore, the VFA infusion noticeably increased basal plasma concentrations of insulin, but it scarcely changed the basal levels of glucagon, SRIF and glucose. From these results we conclude that an increase in the ruminal VFA concentration, even within the physiological range, would suppress GH secretion from the ovine anterior pituitary, and that the postprandial rise in the ruminal VFA concentration may be one of the factors normally suppressing GH secretion in sheep.

Insulin and glucagon secretion in goats (Capra hircus Linnaeus) exposed to cold

Cold exposure significantly decreased the insulin response to the intravenous injection of arginine, butyrate and tolbutamide, and tended to reduce the response to glucose in goats. The glucagon responses to these test materials were not different between warm and cold environments. Intravenous phentolamine infusion tended to increase, and propranolol infusion decreased insulin secretion more effectively in the cold than in the warm environment. It is concluded that cold exposure decreases insulin secretion in response to a variety of stimuli in goats.

Insulinotropic action of human glicentin in dogs

Glicentin has been demonstrated to be released in response to the intraluminal administration of nutrients, but its biological action remains unknown. To clarify the effect of glicentin on the endocrine function of the pancreas, the present study was performed using an in vivo local circulation system of the canine pancreas. During infusion of 0.5% solution of glucose or arginine, 100 and 400 pmol glicentin and 400 pmol glucagon were administered into the pancreaticoduodenal artery (PA) within 10 minutes at 40-minute intervals successively. During glucose infusion, blood glucose in the femoral artery did not change following administration of 100 pmol glicentin, but slightly increased following 400 pmol glicentin. Plasma insulin (immunoreactive insulin [IRI]) in the pancreaticoduodenal vein (PV) increased significantly only following infusion of 400 pmol glicentin. Plasma glucagon (immunoreactive glucagon [IRG]), measured with a specific antiserum to the C-terminal portion of glucagon, did not change following administration of 100 pmol glicentin, but was slightly elevated following 400 pmol glicentin. Plasma total IRG, measured with a nonspecific antiserum, increased promptly after administration of 100 and 400 pmol glicentin. During arginine infusion, the response of plasma IRI to glicentin was markedly exaggerated both in dosages of 100 and 400 pmol. From the present study it was concluded that human glicentin clearly increases insulin release from the canine pancreas.

Effect of C-terminal fragments of glucagon on insulin secretion in dogs

Although the insulinotropic action of glucagon is well known, which parts of the glucagon molecule play an important role in its action remain to be elucidated. To investigate the direct effect of the C-terminal peptides of glucagon on the endocrine function of the pancreas, glucagon (17-29), (21-29), (23-29), and (25-29) were studied using an in situ local circulation system of the canine pancreas. These glucagon fragments, as well as glucagon(1-29), were infused into the superior pancreaticoduodenal artery (PA) in a dosage of 400 pmol for 10 minutes during 0.5% glucose or 0.5% arginine infusion, and plasma insulin (IRI) and glucagon (IRG) levels in the superior pancreaticoduodenal vein (PV) were determined. During the glucose infusion, plasma IRI increased significantly following the administration of glucagon(23-29), (21-29), (17-29), or (1-29), but not glucagon(25-29). In these experiments, plasma IRG increased significantly following infusion of glucagon(21-29), (17-29), or (1-29). During the arginine infusion, all of the glucagon fragments studied enhanced insulin secretion, whereas plasma IRG was increased following the administration of glucagon(21-29), or (1-29). In these experiments with glucose or arginine infusion, blood glucose in the femoral artery (FA) did not change significantly except for glucagon(1-29), which increased the blood glucose level. In addition, the administration of graded doses of glucagon(21-29) [50, 150, and 400 pmol] during the glucose infusion elicited an increase in plasma IRI in a dose-related manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effect of volatile fatty acids on GRF-induced GH secretion in sheep

The effect of intravenous infusion of acetate, propionate and butyrate (0, 3, 10, 30 mumol kg-1 min-1 over 40 min) on the secretion of growth hormone (GH), insulin and glucagon in response to growth hormone-releasing factor (GRF) injection (0.25 micrograms/kg, 10 min after the onset of acid infusion) was determined in six sheep. The intravenous injection of GRF caused a marked increase in plasma GH at every dose of each acid. The GH response to GRF was unaffected by an intravenous infusion of acetate. The basal plasma levels of insulin, glucagon and glucose were unchanged by acetate infusion. The infusion of propionate markedly suppressed the GH response to GRF in a dose-dependent manner. Propionate produced increases in plasma insulin, glucagon and glucose concentrations. Butyrate infusion also caused a significant attenuation of GRF-induced GH secretion. Butyrate infusion stimulated the secretion of both insulin and glucagon and caused hyperglycemia. After cessation of the infusion of propionate or butyrate plasma GH tended to increase again. Plasma somatostatin concentrations, which were measured only for the highest dose of butyrate, were unchanged during acid infusion, but increased on discontinuing the infusion. It is concluded that propionate and butyrate suppress GH secretion, while stimulating the secretion of insulin and glucagon in sheep.

Mechanism of insulin secretion by midaglizole

Midaglizole was introduced as a hypoglycemic agent, but its insulin releasing mechanism remains unknown. In the present study, the effect of midaglizole upon the B cell function of the pancreas was investigated, using an in situ local circulation of the canine pancreas. The graded doses of midaglizole (0.2, 1.0 and 2.0 mg/kg) revealed a dose-related response of plasma insulin. The administration of yohimbine, a classical alpha 2-antagonist (1.11 mg/kg) revealed a similar increase in plasma insulin to that with midaglizole of equimolar amount. During the clonidine infusion midaglizole did not elicit any significant rise in plasma insulin, whereas yohimbine increased plasma insulin significantly. During glucagon infusion plasma insulin increased following midaglizole infusion but not by yohimbine. The simultaneous administration of diazoxide (K-channel opener) suppressed the midaglizole-induced insulin secretion. These results obtained in the present experiments revealed a different mechanism of insulin releasing action of midaglizole from that of yohimbine. Furthermore, the finding with diazoxide administration suggests that midaglizole stimulates insulin release through an interaction of K(+)-channel of the pancreatic B-cell.

Insulin releasing action of N-terminal peptides of glucagon in dogs

The relationship between the molecular structure and insulin releasing action of glucagon remains unknown. In order to investigate the direct action of N-terminal peptides of glucagon, glucagon (1-14), and glucagon (1-21) were studied using an in situ local circulation of the canine pancreas. These glucagon fragments as well as glucagon (1-29) were infused into the superior pancreaticoduodenal artery in a dose of 400 pmol for 10 min during the glucose or arginine infusion, and plasma insulin and glucagon in the superior pancreaticoduodenal vein were determined by radioimmunoassay. During the glucose infusion, glucagon (1-14) elicited a slight increase in plasma insulin, whereas glucagon (1-21) and (1-29) revealed significant changes in plasma insulin. In these experiments plasma glucagon did not change significantly following the administration of glucagon (1-14) or (1-21). During the arginine infusion all of the glucagon fragments studied enhanced insulin secretion markedly, whereas glucagon secretion was not affected. Furthermore, graded doses of glucagon (1-14) (50, 150, and 400 pmol) elicited an increase in plasma insulin in a dose-related manner. It is concluded from the present study that the N-terminal peptides of glucagon stimulate insulin release especially during the arginine infusion.

The structure-function relationship of GLP-1 related peptides in the endocrine function of the canine pancreas

In order to clarify the relationship between the structure and function of glucagon-like peptide (GLP) 1 in the endocrine function of the pancreas, the response of insulin and glucagon to various synthetic GLP-1-related peptides was investigated in anesthetized dogs. GLP-1-related peptides were administered in a dosage of 400 pmol within 10 min into the pancreatic artery during glucose or arginine infusion and the changes in plasma insulin and glucagon in the pancreatic vein were studied. GLP-1 (7-36) and (7-37), as well as glucagon enhanced insulin release during glucose infusion, whereas neither GLP-1 (1-37), (7-20), (6-37) nor (8-37) stimulated insulin release. The administration of GLP-1 (1-37), (7-36) and (7-37) reduced glucagon release during glucose infusion. When arginine was infused, GLP-1 (7-20), (7-36), (7-37), and glucagon enhanced insulin release. In contrast, glucagon release was increased by the administration of GLP-1 (7-20), (8-37), and (7-37). The present study indicates that histidine at the 7th position of GLP-1 is important in eliciting biological action and that only truncated GLP-1 (7-36), (7-37), and (7-20) showed an insulinotropic action as strong as glucagon in dogs. Furthermore, it is suggested that the response of insulin and glucagon to GLP-1-related peptides is dependent on a background condition.

Alpha 2-adrenergic modulation of glucagon and insulin secretions in sheep

To investigate the effects of alpha 2-adrenergic receptors on the secretions of pancreatic glucagon and insulin, clonidine, midaglizole and yohimbine were intravenously administered in four conscious sheep. Clonidine infusion at a dosage of 1.0 nmol/kg/min produced hyperglucagonemia, hypoinsulinemia and hyperglycemia. Midaglizole or yohimbine was infused for 30 min, at doses of 5, 10 and 50 nmol/kg/min during the clonidine infusion. The highest yohimbine infusion (50 nmol/kg/min) blocked the clonidine-induced responses of glucagon, insulin and glucose. On the other hand, the midaglizole (50 nmol/kg/min) infusion brought about no statistical effect on the clonidine-induced responses of glucagon, insulin and glucose. The alpha 2-adrenergic antagonistic effect of midaglizole was clearly less than that of yohimbine in the present experiments. It is concluded that the glucagon secretion is enhanced and the insulin release is inhibited by alpha 2-adrenergic stimulation in conscious sheep.

Effects of intravenous infusion of 17 amino acids on the secretion of GH, glucagon, and insulin in sheep

The effects of intravenous infusion of 17 amino acids, each at a dose of 3 mmol/kg over 30 min, on the secretion of insulin, glucagon, and growth hormone (GH) were studied in 6 castrated male sheep. Insulin-like growth factor I (IGF-I) secretion was also studied using eight of the amino acids. Plasma alpha-amino nitrogen reached a peak at 30 min followed by a gradual decrease thereafter. The greatest increase was obtained using aspartic acid and the smallest with methionine, responses to the remaining amino acids lying between these two. Leucine was the most effective amino acid in stimulating insulin secretion but did not produce any increase in glucagon and GH secretion. Alanine, glycine, and serine induced a greater enhancement of both glucagon and insulin secretion than other amino acids. No amino acid was able to specifically stimulate glucagon secretion without also increasing insulin or GH secretion. With regard to insulin and glucagon secretion, amino acids could be divided into groups according to their R groups. Neutral straight-chain amino acids stimulated both insulin and glucagon secretion, with a greater secretory response to shorter C-chain amino acids. Branched-chain amino acids tended to enhance insulin and suppress glucagon secretion. Acidic amino acids caused an increase in GH secretion. Aspartic acid caused the strongest stimulation of GH secretion, exceeding that induced by arginine. No changes in plasma IGF-I were brought about by any of the amino acids tested.

Role of autonomic nervous system in the response of plasma pancreatic polypeptide to glycopenia in dogs

The effect of cholinergic and adrenergic influences on pancreatic polypeptide (PP) release was studied in dogs. Administration of acetylcholine resulted in an elevation of plasma PP, whereas epinephrine induced no increase. Insulin-induced hypoglycemia increased plasma PP in a conscious state but not in anesthetized dogs. The infusion of phentolamine or propranolol did not affect the response of plasma PP to insulin-induced hypoglycemia, whereas atropine markedly inhibited the increase in plasma PP. Likewise, atropine reduced the rise of plasma PP during the intravenous administration of 2-deoxy-D-glucose (2-DG). We conclude from the present experiments that cholinergic mechanisms are of major importance in the response of PP to insulin- and 2-DG-induced glucoprivation, while the major role of the adrenergic mechanism was not proved.

Increased plasma glucagon-like immunoreactivity in dogs with ileojejunal transposition

To elucidate hormonal and metabolic changes in intestinal adaptation, an experimental study was performed in dogs subjected to ileojejunal transposition. Fasting levels of blood glucose, plasma insulin and gastric inhibitory polypeptide (GIP) did not change significantly throughout 12 weeks. Plasma glucagon measured with an antiserum specific to the C-terminal portion of glucagon slightly increased and plasma total glucagon measured with a non-specific antiserum gradually increased. Glucose tolerance deteriorated at the 4th week in the transposed group. The response of plasma insulin and GIP to glucose in the transposed group did not differ from that of the sham operated group. Plasma glucagon increased significantly during glucose loading at the 12th week. The response of plasma total glucagon to glucose was most prominent, reaching a peak of 3,755 +/- 742 pmol/liter. The value was significantly increased, compared with that of the sham group or normal group (p less than 0.01). Insulin-induced hypoglycemia enhanced a larger increment of plasma total glucagon in the transposed group than in the sham group (p less than 0.05). At the 12th week plasma total amino acids were decreased and several amino acids were reduced. It is concluded that ileojejunal transposition elicited an exaggerated response of plasma total glucagon to glucose and several metabolic derangements and that the transposition offers an excellent model for hyperenteroglucagonemia.

Effect of a new lente insulin on diabetics

Thirty diabetics who had been receiving ordinary insulin were switched to S-lente insulin, a new mixture of four parts semilente and six parts ultralente insulin. Eight times a day, we measured the glucose, insulin, and C-peptide (CPR) in their blood. Those with more than 250 mg/dl postprandial glucose were designated group A (18 patients) and the other were designated group B (12 patients). Group A diabetics experienced a significant decrease in fasting blood glucose levels whereas group B did not. S-lente improved the daily blood glucose profiles of 72% of group A and 25% of group B. It slightly reduced the sum of the daily blood glucose in group A and did not affect those of group B. The M-value fell significantly in group A but not in group B. Changes in this value correlated significantly with those of blood glucose determination sums. The sums of the determinations of free plasma insulin and CPR remained unaffected by the new insulin. It is concluded that S-lente insulin controls the blood glucose of diabetics whose postprandial blood glucose cannot be controlled by ordinary insulin.

Effect of porcine pancreastatin on endocrine function of canine pancreas

Controversial results concerning the modulation of insulin release with pancreastatin prompted us to investigate the effect of this peptide upon the endocrine function of the pancreas using an in situ perfusion method in dogs. Administration of porcine pancreastatin into the pancreaticoduodenal artery in a dosage of 0.34 micrograms/kg of body weight during arginine infusion increased slightly plasma insulin and lowered minimally plasma glucagon in the pancreaticoduodenal vein. Pancreastatin infusion in a dosage of 500 ng/min did not modify glucose-induced insulin release and glucagon suppression by glucose. Theophylline infusion induced a slight increase in plasma insulin and glucagon in the pancreaticoduodenal vein. Pancreastatin infusion accelerated slightly these changes in plasma insulin and glucagon following theophylline infusion. From the present experiment it is concluded that porcine pancreastatin did not inhibit glucose-induced insulin release from the canine pancreas, inconsistent with the first report on insulin release from the rat pancreas. Alternatively, porcine pancreastatin rather stimulated insulin release during arginine infusion or following theophylline administration.

Response of gut glucagon-like immunoreactivity to hypoglycemia in dogs

Previous studies demonstrated that insulin-induced hypoglycemia enhances glicentin secretion in piglets and prompted us to investigate the response of glucagon-like immunoreactivity (GLI) to hypoglycemia in dogs. Insulin hypoglycemia did not induce any rise of plasma total immunoreactive glucagon (IRG) measured by nonspecific antiserum to glucagon in normal or pancreatectomized dogs under anesthesia. In contrast, insulin-induced hypoglycemia clearly increased plasma total IRG in both normal and pancreatectomized dogs in a conscious state. Administration of acetylcholine resulted in an elevation of plasma total IRG, whereas epinephrine induced a slight increase in plasma total IRG. The infusion of alpha- or beta-adrenergic blockers did not affect the response of plasma total IRG to hypoglycemia, whereas atropine completely blunted the increase in plasma total IRG during insulin hypoglycemia. Similarly atropine abolished the rise of plasma total IRG during intravenous administration of 2-deoxy-D-glucose. It is concluded that hypoglycemia clearly enhances the secretion of GLI from the gut in dogs and that GLI secretion during hypoglycemia is modulated, at least in part, by the autonomic nervous system.

Effect of intraluminal administration of amino acids upon plasma glicentin

To see what effect intraluminal amino acids would have on glicentin secretion, we put a mixture of 10 amino acids (1 g/kg) into the duodenum of five normal, conscious piglets. Their plasma nitrogen rose, as did insulin and glucagon measured with C-terminal-specific antiserum. Plasma total immunoreactive glucagon, determined with non-specific antiserum, rose from 2753 +/- 460 pg/ml to a peak of 4434 +/- 1352 pg/ml at 30 min. Plasma glicentin, determined with R 64 antiserum, rose from a fasting level of 297 +/- 70 pmol/l to a peak of 702 +/- 167 pmol/l at 45 min. We also gave oral arginine to 6 pancreatectomized dogs to investigate why the plasma glicentin rises after amino acid ingestion. Arginine raised the plasma total immunoreactive glucagon from 1120 +/- 214 pg/ml to a peak of 2266 +/- 512 pg/ml at 45 min. We conclude that intraluminally administered amino acids enhance glicentin secretion from the gut.

Effect of glicentin-related peptides upon the secretion of insulin and glucagon in the canine pancreas

In order to clarify responses of the endocrine pancreas to glicentin, four glicentin-related peptides were investigated in a local circulation preparation of the canine pancreas. These peptides were administered in a dosage of 200 pmole for 10 min into the pancreaticoduodenal artery under the continuous infusion of 0.5% arginine solution. In a group of six dogs, the administration of glicentin-related pancreatic peptide (GRPP) and glicentin 1-16 resulted in an increase in plasma insulin (IRI) and a decrease in plasma glucagon (IRG). In the other group of six dogs, the administration of glicentin 62-69 induced an increase in plasma IRI and a decrease in plasma IRG. Following the successive infusion of oxyntomodulin, both plasma IRI and IRG increased slightly. Porcine glucagon administered at the end of each experiment exerted a rise in blood glucose and plasma IRI in addition to an increase in plasma IRG. In comparison of the maximal responses of plasma IRI and IRG to these glicentin-related peptides, the administration of glicentin 1-16, 62-69 or GRPP elicited an increase in plasma IRI and a decrease in plasma IRG. In contrast, oxyntomodulin and glucagon increased both plasma IRI and IRG. The present study indicates that glicentin-related peptides, both the N- and C-terminal portions, affect the endocrine function of the pancreas and suggests that glicentin released by nutrient ingestion plays an important role in the enteroinsular axis.

Adrenergic modulation of pancreatic glucagon and insulin secretion in sheep

The effect of intravenous infusion of epinephrine, either alone or together with various doses of phentolamine or propranolol, on the secretion of both glucagon and insulin was determined in six sheep. Intravenous infusion of epinephrine alone caused increases in plasma glucagon and glucose concentrations and produced a slight but significant decrease in plasma insulin concentration. The concomitant infusion of propranolol and epinephrine augmented glucagon release and inhibited insulin secretion. Combined propranolol plus epinephrine infusion also caused a marked hyperglycemia. The concomitant infusion of phentolamine and epinephrine produced slight inhibition of glucagon secretion and markedly promoted insulin secretion. Epinephrine-induced hyperglycemia was eliminated by phentolamine infusion. The effects of isoproterenol infusion on plasma glucagon, insulin, and glucose concentrations were similar to that caused by the concomitant infusion of phentolamine and epinephrine. The effects of isoproterenol were abolished by the infusion of propranolol. It is concluded that an alpha-receptor mechanism is the most important component of adrenergic modulation of pancreatic glucagon secretion, whereas beta-receptor activation stimulates and alpha-receptor activation inhibits insulin secretion in sheep.

Effect of ileo-jejunal transposition on intestinal adaptation after total colectomy in dogs

The effect of ileo-jejunal transposition (IJT) on the intestinal adaptation after total colectomy was investigated in 4 mongrel dogs. Hyperenteroglucagonemia was observed in the IJT with colectomy group, especially in postprandial state. Obvious hyperplastic changes were observed in all part of the small intestinal mucosa in the colectomy with IJT group. However, there were no significant differences in body weight changes between the colectomy with IJT group and the colectomy group. Postprandial plasma gastrin levels were lower in the colectomy with IJT group compared to the control. These results suggest that IJT causes hyperenteroglucagonemia and intestinal mucosal hypertrophy in colectomized dogs. Enteroglucagon may have an inhibitory effect on postprandial gastrin release.

Response of plasma glicentin to intraduodenal administration of glucose in piglets

Controversial results concerning the secretion of glicentin prompted us to investigate the response of circulating glicentin to intraduodenal administration of glucose in piglets. A 20% solution of glucose (2 g/kg) was administered into the duodenum of six piglets in a fully conscious state. As blood glucose rose, plasma insulin increased to a peak of 21 +/- 4 microU/ml. Plasma glucagon, determined by C-terminal-specific antiserum, was 70 +/- 30 pg/ml at fasting and slightly increased after the glucose load. Plasma immunoreactive glucagon measured by cross-reacting glucagon antiserum increased from the baseline of 1563 +/- 260 to a peak of 4738 +/- 415 pg/ml at 120 min. Plasma glicentin determined by antiserum R 64 was 463 +/- 81 pmol/l at baseline and reached a peak level of 1081 +/- 174 pmol/l at 90 min. The percent changes of plasma glucagon from the fasting level measured by cross-reacting antiserum and glicentin were 296 and 233%, respectively. There was a significant correlation between plasma glucagon measured by cross-reacting antiserum and glicentin (r = 0.817, P less than 0.001). Chromatography of plasma obtained during glucose load revealed the heterogeneity of glicentin. It can be concluded from the present study that glicentin is clearly secreted in response to intraluminal administration of glucose.

Response of plasma glicentin to fat ingestion in piglets

In order to elucidate the response of plasma glicentin to fat ingestion, butter, glycerol or palmitate was administered into the duodenum of piglets in a fully conscious state and plasma glicentin and glucagon were determined. Butter instillation did not change blood glucose. Plasma triglyceride rose gradually 120 min after butter loading. Plasma insulin and glucagon measured by antiserum specific to the C-terminal slightly increased following butter administration and plasma total glucagon and glicentin increased gradually and significantly. The increments of total glucagon and glicentin were 179 and 158%, respectively. However, chromatography of porcine plasma obtained during fat loading revealed heterogeneity of glicentin-related peptides. Glycerol ingestion induced a slight rise of plasma total glucagon. Administration of palmitate revealed an increase in plasma total glucagon and glicentin. The present study clearly demonstrates the secretion of glicentin following fat ingestion, which might be caused by the hydrolysates of triglyceride, as suggested in previous dog experiments.

The role of humoral factors and the ileocecal valve in pathological changes occurring after distal small bowel resection

Experimental studies using dogs were performed to elucidate the participation of gastrointestinal hormones as well as the ileocecal valve in postoperative sequelae following massive small bowel resection. Although in both the ileal resection and the ileocecal resection groups the absorption of fat was reduced postoperatively, body weight tended to increase in the former, while it decreased gradually in the latter. In addition, watery diarrhea persisted after ileocecal resection. Plasma total bile acid concentrations in each group were lower than those before surgery, as were plasma levels of both total glucagon and neurotensin. Although differences were not significant, plasma neurotensin levels tended to be higher after ileocecal resection, but plasma total glucagon levels tended to be lower. Plasma gastric inhibitory polypeptide (GIP) response to butter ingestion was also lower after both ileal and ileocecal resection; especially in the latter case the decrease was significant. These results indicate that the diminished plasma levels of neurotensin, enteroglucagon and GIP may be related to the impairment of adaptive changes in the remaining small intestine.

Glucose-induced responses of insulin and gastric inhibitory polypeptide in various animal models

In order to clarify the role of gastric inhibitory polypeptide (GIP) in an enteroinsular axis, 19 healthy mongrel dogs were divided into following groups: 5 normal dogs (N), 4 dogs with gastrojejunostomy (GJ), 5 dogs with duodenal fistula (D) and 5 vagotomized dogs (V). Four weeks after the operation glucose was administered orally or intraduodenally in a conscious state. In group D, glucose administration was repeated under atropine injection (A). Glucose-induced response of plasma GIP was exaggerated in all the groups compared with group N. The regression equation reported by Lauritsen and Moody was obtained in each dog from the ratio of plasma insulin to blood glucose and from plasma GIP. The slope of the regression line was elevated in group GJ and reduced in group V. However, groups D and A did not reveal any difference in the slope of the regression line compared with group N. From the present study, it might be concluded that the B-values in Lauritsen and Moody's equation indicates the sensitivity of the B cell in the pancreatic islet and that GIP secretion plays an important role in the glucose-induced insulin response even in the conditions with various surgical modifications.

Effect of glicentin-related peptides on glucagon secretion in anaesthetized dogs

Recent studies have demonstrated that glicentin is released during nutrient ingestion. However, the biological function of glicentin remains unclear. In order to clarify the role of glicentin in the enteroinsular axis, the effect of glicentin-related peptides was investigated using in vivo local circulation of canine pancreas. Peaks I and II of gut glucagon-like immunoreactivity, partially purified from porcine intestinal extract by affinity chromatography and gel filtration, synthesized hexadecapeptide of N-terminal glicentin (1-16) and synthesized octapeptide of C-terminal glicentin (62-69) were administered for 10 min into the pancreaticoduodenal artery of canine pancreas. Blood samples were then drawn from the pancreaticoduodenal vein. The administration of peak I of glucagon-like immunoreactivity during arginine infusion in a dosage of 20 ng reduced the glucagon secretion by 42 pmol/l (p less than 0.05), whereas peak II of glucagon-like immunoreactivity (20 ng) slightly increased the plasma level of insulin, although not significantly. The administration of glicentin (1-16) in a dosage of 400 ng during saline infusion did not alter the plasma insulin level, but reduced the plasma glucagon level in the pancreaticoduodenal vein by 29 pmol/l (p less than 0.05). In addition, glicentin [62-69] in a dosage of 400 ng exerted a decrease in both the plasma insulin (40 mU/l, p less than 0.05) and glucagon level (27 pmol/l, p less than 0.05). The present study demonstrates the suppression of pancreatic glucagon release during the infusion of peak I glucagon-like immunoreactivity and N- or C-terminal glicentin-related peptide. Therefore, it is suggested that glicentin released during nutrient intake might inhibit the secretion of glucagon.

Gastric acid secretion and gut hormone release in patients undergoing pancreaticoduodenectomy

The changes in gastric acid secretion and gut hormone release were investigated in 11 patients who underwent pancreaticoduodenectomy. The amount of acid output showed normoacidity before surgery and hypoacidity after surgery. No peptic ulcers were detectable after surgery. Plasma gastrin levels were markedly reduced after surgery both in the fasting state and after a test meal loading. Although fasting plasma levels of both gastric inhibitory polypeptide (GIP) and insulin after surgery were close to those before surgery, the response of these hormones to the meal was significantly reduced after surgery. On the other hand, blood glucose concentrations increased gradually after feeding, and the elevation was greatly prolonged after surgery compared with preoperative levels. From these results, it is concluded that peptic ulcer will not occur if subtotal gastrectomy is performed during Whipple's procedure. It is presumed that the diminished release of gut hormones such as gastrin, GIP, and insulin was due to the massive resection of the distal stomach, the upper small intestine, and the head of the pancreas and to the diversion of the stream of food from the duodenum to the jejunum. It is also assumed that the glucose-dependent insulinotropic action of GIP would be impaired by the procedure.

Adrenergic modulation of pancreatic glucagon and insulin secretion in goats

Five goats were used to investigate adrenergic influences on the secretion of both glucagon and insulin. The secretion of glucagon was augmented via alpha-adrenergic stimulation. The secretion of insulin was enhanced by stimulation of beta-adrenergic receptors and inhibited by alpha-adrenergic stimulation.

Role of vagus nerve in secretion of gastric inhibitory polypeptide in dogs

In order to clarify the role of the vagus nerve in the secretion of gastric inhibitory polypeptide (GIP), experiments were performed on dogs. Response of plasma GIP to intraduodenal instillation of glucose was slightly lower in a group which received atropine, than in a group of normal dogs. The response of plasma GIP to intraduodenal glucose load was not different between vagotomized dogs and normal dogs. Electric stimulation of the vagus nerve did not produce any significant changes in plasma GIP in anesthetized dogs. In conclusion, the present study indicates that the role of the vagus nerve on GIP secretion is tiny, if any, and that the nervous influence does not overcome the effect of intraluminal administration of glucose.

Response of extrapancreatic glucagon to gastrointestinal hormones in pancreatectomized dogs

In order to investigate the effect of gastrointestinal hormones upon the secretion of extrapancreatic glucagon, tetragastrin, secretin, caerulein and cholecytokinin-pancreozymin octapeptide (CCK-octa) were administered during saline or arginine infusion in pancreatectomized dogs. Intravenous administration of tetragastrin (7 micrograms/kg) did not elicit any changes in plasma glucagon during saline infusion, while the plasma glucagon increased significantly following tetragastrin infusion during arginine infusion. The administration of secretin (3 U/kg) did not affect the plasma level of glucagon during saline or arginine infusion at all. Plasma glucagon did not change after the administration of caerulein (0.5 microgram/kg) during saline infusion, whereas it increased significantly following caerulein administration during arginine infusion. Intravenous administration of CCK-octa in a dose of 20 U/kg did not affect the plasma level of glucagon during saline infusion but exerted a significant rise of extrapancreatic glucagon during arginine infusion. It is concluded from the present experiment that the administration of tetragastrin, caerulein or CCK-octa enhances the release of extrapancreatic glucagon stimulated by arginine infusion while secretin infusion does not affect the secretion of extrapancreatic glucagon.

Secretion of glucagon in liver cell carcinoma

In order to elucidate the response of plasma glucagon in liver cell carcinoma, a clinical study was performed in 12 patients with liver cell carcinoma in addition to 8 patients with liver cirrhosis and 8 normal subjects. Arginine infusion elicited increases in plasma insulin and glucagon in 6 patients with liver cell carcinoma as well as 8 patients with liver cirrhosis compared with the controls. However, the responses of plasma insulin and glucagon in liver cell carcinoma did not exceed those in liver cirrhosis. No glucagon secreting cell was proved in the hepatic cancer tissues from two other patients. Furthermore, no measurable glucagon was demonstrated in the tumor tissues extracted from four other patients with liver cell carcinoma. The extract of the tumors, infused into the pancreatic artery of anesthetized dogs, did not elicit any discernible changes in glucagon and insulin in the pancreatic vein. The present study demonstrates an elevated response of plasma glucagon in liver cell carcinoma. Since the morphological and biochemical studies failed to demonstrate the glucagon secreting cell or glucagon-stimulating material in the tumor tissues, the elevated plasma glucagon response might be interpreted by the increased A-cell function of the pancreas and the decreased degradation of the hormones in the liver.

Gastric acid secretion and gastrin and gastric inhibitory polypeptide release in cirrhotic patients

Gastric acid secretion, incidence of gastric mucosal lesion, and gut hormone responses were studied in 24 patients with liver cirrhosis. Gastric acid output in these subjects showed normal acidity and was nearly similar to that in patients with gastric ulcer. The incidence of gastric mucosal lesion was high, especially in patients whose plasma disappearance rate of indocyanine green was low. Plasma levels of both gastrin and gastric inhibitory polypeptide were higher in cirrhotic patients than in control subjects both in the fasting state and after the ingestion of a test meal. Gel chromatography of the postprandial plasma of cirrhotics showed a higher immunoreactivity at the second peak than in controls. This is because cirrhotics have a higher percentage of authentic gastric inhibitory polypeptide, although the elution patterns were similar in both groups. It is suggested that impairment of extraction of some molecular components of both gastrin and gastric inhibitory polypeptide may occur in the cirrhotic liver.

Characterization of response of gut GLI to fat ingestion in dogs

Previous study from our laboratory demonstrated that an increased release of gut glucagon-like immunoreactivity (GLI) following triglyceride digestion was not observed in pancreatectomized dogs. Therefore, in order to clarify the response of gut GLI to triglyceride ingestion, experimental study was carried out in normal and pancreatectomized dogs. When butter was administered to pancreatectomized dogs in combination with pancreatic enzymes, plasma glucagon (IRG) measured by specific antiserum did not change significantly but plasma triglyceride as well as plasma total immunoreactive glucagon (total IRG) measured by nonspecific antiserum increased. Oral administration of glycerol induced no significant increase in plasma IRG but elicited a moderate increase of plasma total IRG. Gastric instillation of palmitic acid induced a remarkable rise of plasma total IRG in normal dogs, whereas plasma IRG did not reveal any changes. Oral administration of triglyceride of medium chain fatty acid, tricaprylin, did not promote any rise of plasma IRG but a slight increase of plasma total IRG. From the present experiment, it is concluded that hydrolysis of triglyceride and its metabolites are important in the release of gut GLI following fat ingestion. Among its metabolites, long chain fatty acid and glycerol promote the GLI secretion, whereas medium chain fatty acid does not.

Insulin and glucagon in spontaneously diabetic non-obese mice

To investigate the role of glucagon in the development of diabetes mellitus, spontaneously diabetic non-obese mice were studied before (group 1) and after the onset of diabetes mellitus (group 2). In group 1, fasting blood glucose and insulin in plasma and pancreas did not differ significantly, while plasma glucagon was elevated (48.9 +/- 10.4 versus control 18.6 +/- 6.0 pmol/l). In group 2, the insulin content of plasma and the pancreas were markedly reduced, whereas plasma glucagon was elevated (180.9 +/- 59.1 pmol/l). When diabetic mice were treated with insulin for 4 weeks (group 3), plasma glucagon was markedly reduced compared with that of group 2 (30.3 +/- 9.0 pmol/l). In group 1, glucagon and glucagon-like immunoreactivity of the intestine were reduced. The glucagon content of the intestine was elevated in group 2. Group 3 elicited increased contents of gastric glucagon as well as intestinal glucagon-like immunoreactivity. We conclude that, in addition to insulin deficiency, hypersecretion of glucagon might contribute to the development and clinical course of diabetes mellitus in the non-obese diabetic mouse.

Response of extrapancreatic immunoreactive glucagon to intraluminal nutrients in pancreatectomized dogs

To investigate the response of extrapancreatic glucagon to intraluminal stimuli, nutrients were administered to normal and pancreatectomized dogs through a stomach tube in a fully conscious state after an overnight fast. Plasma immunoreactive glucagon was determined with antisera specific and nonspecific to glucagon and was designated as IRG and total IRG, respectively. Oral glucose load elicited a decrease in plasma IRG and a remarkable rise of plasma total IRG in a group of 6 pancreatectomized dogs, as in the control dogs. When arginine was given, both plasma IRG and total IRG significantly increased in a group of 5 pancreatectomized dogs, while only total IRG rose significantly in the normal control dogs. Butter load did not reveal any changes in plasma IRG and total IRG in a group of 5 pancreatectomized dogs, whereas only total IRG increased in the normal control dogs. It is concluded that extrapancreatic glucagon responds to intraluminal administration of nutrients, as pancreatic glucagon does. In addition, gut glucagon-like immunoreactivity increased following glucose or arginine ingestion in pancreatectomized dogs. Furthermore, the failure in response of plasma IRG and total IRG to butter load in pancreatectomized animals suggests that its intraluminal hydrolysis is important in the secretion of extrapancreatic immunoreactive glucagon.

Influence of vagotomy upon GIP release in patients with peptic ulcer

Twenty-two vagotomized peptic ulcer patients were studied on the influence of vagotomy on the release of GIP. Moreover, the relationship between acid output and GIP release was analyzed. These patients underwent one of the three types of operation; truncal vagotomy with pyloroplasty (TV + P) selective vagotomy with pyloroplasty (SV + P) and selective vagotomy with antrectomy (SV + A). Before and after surgery, a gastric juice study and an oral glucose tolerance test were performed on separate days. Maximum acid output in response to tetragastrin correlated significantly with integrated GIP response after oral glucose loading. In the SV + P group, the response of GIP was slightly greater after surgery. In the SV + A group, the integrated GIP response diminished postoperatively, although, after surgery, GIP reached its peak sooner. The integrated GIP response was greater in the SV + P group than in the TV + P group. The response of GIP was less in the SV + A group than in the SV + P group. These changes were insignificant. In conclusion, it is presumed that GIP release is affected by gastric acid, gastric emptying time, intestinal transit time and vagal nerve action.

Response of gastric inhibitory polypeptide to fat ingestion in normal dogs

Because of the differences in the data concerning the mechanism by which gastric inhibitory polypeptide (GIP) is secreted following fat ingestion, we were prompted to investigate the characteristics of the GIP response to the triacylglycerol components in normal dogs. Oral administration of glycerol (1 g/kg) slightly elevated the blood glucose levels but not the plasma GIP. Palmitate (1 g/kg) administration did not change the blood glucose whereas the plasma GIP was increased remarkably and remained elevated at 120 min. Oral administration of tricaprylin (2 g/kg) did not elicit any discernible changes in the blood glucose nor in the plasma GIP. Column chromatography of plasma obtained from a dog after palmitate ingestion revealed three GIP-immunoreactive peaks: one peak corresponding to the authentic GIP, one to the large molecular weight peak, and one to the small molecular weight peak. Similar results were obtained with the plasma collected after fat ingestion. From the present study, it would appear that hydrolysis of triacylglycerol plays an important role in GIP release from the intestine. Furthermore, it is concluded that the long chain fatty acids stimulate GIP release whereas the medium chain fatty acids do not.

Factors influencing the development of diabetic vascular complications

In order to elucidate the factors influencing the development of diabetic vascular complications, a retrospective clinical study was carried out in 255 patients, who had been treated in our diabetes clinic for more than 10 years. The patients were divided into three groups according to their retinal lesions: group A, 89, had no retinal lesions; group B, 118, Scott I and II; and group C, 48, Scott III or more advanced lesions. Although there were no significant differences in body weight or age at onset of diabetes between the three groups, the severity of the disease at the first visit and the method of treatment were regarded as important factors in the development of vascular complications. Hypertension, albuminuria and hypercholesterolemia were observed more often in group C than groups A and B, while there was no difference in EKG abnormalities between the three groups. No significant difference was demonstrated concerning control of blood glucose, incidence of hypoglycemia, urinary glucose and ketone bodies, serum triglyceride, hemoglobin A1c, beta-N-acetylglucosaminidase or serum lipoperoxide. These results suggest that the complicated mechanism involved in the development of vascular complications should be investigated and a long-term dynamic observation should be carried out.

Response of extrapancreatic glucagon to glycemic changes under chronic insulin deficiency in dogs

Since the secretion of pancreatic glucagon is largely influenced by the changes in the blood glucose level, the response of extrapancreatic glucagon was investigated in totally pancreatectomized dogs under chronic insulin deficiency. Insulin-induced hypoglycemia did not alter plasma glucagon in the portal vein in a group of 5 pancreatectomized dogs, but the decrease of the blood glucose was small, by 70 mg/100 ml, in spite of a large amount of insulin. The administration of 2-deoxyglucose did not cause any changes in plasma glucagon in the portal vein in a group of 6 pancreatectomized dogs. Glucose-induced hyperglycemia, both transient and continuous, did not cause any changes in plasma glucagon in the portal vein, although blood glucose was significantly elevated. It is concluded that regulation of extrapancreatic glucagon differs from that of pancreatic glucagon.

Effects of Ca antagonists, nifedipine, niludipine and verapamil, on endocrine function of the pancreas

To study the effects of two Ca antagonists, nifedipine and niludipine, on insulin and glucagon secretion, experiments were performed using an in situ local circulation of the canine pancreas. The test drugs were injected into the pancreatic artery in three graded doses (5, 10 and 100 nmoles/kg) during arginine infusion, and blood samples were taken from the pancreatic vein. Verapamil, 10, 100 and 1,000 nmoles/kg, administered in the same way, was used as a control drug. Nifedipine, 5 to 100 nmoles/kg, decreased plasma insulin (IRI) and increased plasma glucagon (IRG) in the pancreatic vein, but caused no marked changes of blood glucose levels in five dogs. Niludipine, 5 to 100 nmoles/kg, injected into the pancreatic artery of 5 dogs, did not change blood glucose levels, but decreased slightly plasma IRI in the pancreatic vein and increased plasma IRG. Verapamil administered to 5 dogs caused no remarkable change of blood glucose or plasma IRG but decreased plasma IRI slightly. The maximum secretion of insulin was significantly lowered by nifedipine and niludipine, and that of pancreatic glucagon markedly increased by niludipine. The experiments revealed that Ca antagonists inhibit insulin secretion, and increase glucagon, and proved that calcium plays an important role in the A cell function of the pancreas.

Effect of endogenous gastric inhibitory polypeptide (GIP) on the removal of triacylglycerol in dogs

In order to clarify the effect of endogenous gastric inhibitory polypeptide (GIP) upon lipid metabolism, the removal of intravenously administered triacylglycerol was investigated following an oral glucose or galactose load in dogs. After an overnight fast, the triacylglycerol emulsion was infused at a constant rate of 1 ml/min for 90 min, and glucose, galactose or tap water was orally administered at 30 min. Blood glucose increased after the glucose load but it did not change following the galactose load or water ingestion. Plasma insulin increased after the glucose load but did not change after galactose or tap water ingestion. Plasma glucagon did not show any discernible change in the three experimental groups. Plasma GIP increased following the glucose or galactose load to 4360 or 1653 pg/ml, respectively. Plasma triacylglycerol increased to the same levels at 30 min in the three experimental groups. The peak levels of plasma triacylglycerol and integrated plasma triacylglycerol for 150 min did not differ in the three groups. Moreover, there was no difference in the removal rate of plasma triacylglycerol following the withdrawal of the fat emulsion. It is concluded from the present study that endogenously released GIP does not elicit any effect upon triacylglycerol removal.

Response of gastric inhibitory polypeptide (GIP) to oral administration of nutrients in normal and pancreatectomized dogs

In order to clarify the response of plasma gastric inhibitory polypeptide (GIP) to various nutrients and to investigate the relationship between the pancreas and GIP secretion, an experimental study was performed using normal and pancreatectomized dogs. Oral administration of glucose (2 g/kg) or butter (2 g/kg) resulted in an increase of plasma GIP in five normal dogs. In contrast, oral administration of arginine (1 g/kg) did not produce any discernible changes in plasma GIP in normal dogs. In a group of nine pancreatectomized dogs, the fasting level of plasma GIP did not differ from that of the control group. Furthermore, glucose ingestion in the pancreatectomized group resulted in the same pattern and the same degree of change in plasma GIP as it did in the normal controls. In contrast, plasma GIP did not change at all following fat loading in the pancreatectomized group. However, butter with pancreatic enzymes elicited a significant rise of plasma GIP in the pancreatectomized dogs. The present study indicates that plasma GIP increases following oral administration of glucose or fat but not arginine. Furthermore, it is demonstrated that GIP secretion following fat ingestion occurs only after fat digestion by pancreatic enzymes. In addition, the findings observed in the present study do not support the existence of feedback effect of insulin on GIP secretion.

Measurement of glucagon in human plasma by enzyme immunoassay

In order to investigate the validity of an enzyme immunoassay for glucagon, the glucagon levels of human plasma were determined by both enzyme immunoassay (EIA) and radioimmunoassay (RIA). After a glucose load, plasma glucagon measured by both EIA and RIA fell in 12 normal subjects. The glucagon levels measured by both assays during glucose tolerance test showed good agreement in a group of 10 patients. After arginine infusion, plasma glucagon increased in 6 normal subjects and 3 patients and glucagon values measured by EIA correlated well with those by RIA. The present study demonstrates correlation between glucagon levels measured by RIA and EIA and indicates the usefulness of EIA for determining glucagon in human plasma.