Priming effect of glucagon-like peptide-1 (7-36) amide, glucose-dependent insulinotropic polypeptide and cholecystokinin-8 at the isolated perfused rat pancreas.

The priming effect of glucagon-like peptide-1 (7-36) amide (GLP-1 (7-36) amide), glucose-dependent insulin-releasing polypeptide (GIP) and cholecystokinin-8 (CCK-8) on glucose-induced insulin secretion from rat pancreas was investigated. The isolated pancreas was perfused in vitro with Krebs-Ringer bicarbonate buffer containing 2.8 mmol/l glucose. After 10 min this medium was supplemented with GLP-1 (7-36) amide, GIP or CCK-8 (10, 100, 1000 pmol/l) for 10 min. After an additional 10 min period with 2.8 mmol/l glucose alone, insulin secretion was stimulated with buffer containing 10 mmol/l glucose for 44 min. In control experiments the typical biphasic insulin response to 10 mmol/l glucose occurred. Pretreatment of the pancreas with GIP augmented insulin secretion: 10 pmol/l GIP enhanced only the first phase of the secretory response to 10 mmol/l glucose; 100 and 1000 pmol/l GIP stimulated both phases of hormone secretion. After exposure to CCK-8, enhanced insulin release during the first (at 10 and 1000 pmol/l CCK-8) and the second phase (at 1000 pmol/l) was observed. Priming with 100 pmol/l GLP-1 (7-36) amide significantly amplified the first and 1000 pmol/l GLP-1 (7-36) amide both secretion periods, 10 pmol/l GLP-1 (7-36) amide had no significant effect. All three peptide hormones influenced the first, quickly arising secretory response more than the second phase. Priming with forskolin (30 mM) enhanced the secretory response to 10 mM glucose plus 0.5 nM GLP-1 (7-36) amide 4-fold. With a glucose-responsive B-cell line (HIT cells), we investigated the hypothesis that the priming effect of GLP-1 (7-36) amide is mediated by the adenylate cyclase system. Priming with either IBMX (0.1 mM) or forskolin (2.5 microM) enhanced the insulin release after a consecutive glucose stimulation (5 mM). This effect was pronounced when GLP-1 (7-36) amide (100 pM) was added during glucose stimulation. Priming capacities of intestinal peptide hormones may be involved in the regulation of postprandial insulin release. The incretin action of these hormones can probably, at least in part, be explained by these effects. The priming effect of GLP-1 (7-36) amide is most likely mediated by the adenylate cyclase system.     

The effects of γ-hexachlorocyclohexane on amylase secretion and inositol phospholipid metabolism in mouse pancreatic acini

Dispersed mouse and guinea-pig pancreatic acini were used to examine the effects of the inositol analogue, γ-hexachlorocyclohexane (lindane) on agonist-stimulated amylase secretion. Secretion from mouse acini in response to carbachol and cholecystokinin octapeptide (CCK-8) was reduced by lindane. Similarly, amylase release from guinea-pig acini stimulated by carbachol was abolished by lindane. These acini, however, still remained responsive to dibutyryl-cAMP with only a slightly diminished secretion to this agent. Inositol phospholipid synthesis and hydrolysis was stimulated in mouse acini by both carbachol and CCK-8. Although hydrolysis of these lipids in response to CCK-8 was reduced by only 18%, stimulation of inositol phospholipid synthesis by either agonist was abolished by lindane. Dose-response curves for inositol phospholipid synthesis stimulated by carbachol and CCK-8 in mouse acini were biphasic and superimposable with those of amylase secretion. In contrast, the dose-response curve for phosphoinositide hydrolysis was sigmoid and clearly separable from that of synthesis. Reducing the external Ca²⁺ concentration caused the dose-response curves for carbachol- and CCK-8-induced inositol phospholipid synthesis to be displaced to the right, as has been observed for amylase secretion. A23187 was also found to induce amylase secretion and inositol phospholipid synthesis, and both of these responses were inhibited by lindane. Amylase secretion and inositol phospholipid synthesis may, therefore, be closely related events in the exocrine pancreas. Lindane may provide a valuable tool with which to determine the role of inositol phospholipid metabolism in stimulus-response coupling.     

Effects of GP2 expression on secretion and endocytosis in pancreatic AR4-2J cells

GP2 is the major membrane protein present in secretory granules of the exocrine pancreas. GP2's function is unknown, but a role in digestive enzyme packaging or secretion from secretory granules has been proposed. In addition, GP2 has been proposed to influence endocytosis and membrane recycling following stimulated secretion. Adenovirus-mediated GP2 overexpression in the rat pancreatic cell line AR4-2J was used to study its impact on digestive enzyme secretion and membrane recycling. Immunoelectron microscopy showed that GP2 and amylase co-localized in secretory granules in infected AR4-2J cells. CCK-8 stimulation resulted in a fourfold increase in amylase secretion with or without GP2 expression. GP2 expression also did not influence endocytosis following CCK-8 stimulation. Thus, GP2 expression in AR4-2J cells does not affect amylase packaging in secretory granules or stimulated secretion. GP2 expression also does not influence membrane recycling in response to stimulated stimulation in AR4-2J cells.     

An in vitro evaluation of adrenergic action on rat pancreatic amylase secretion: lack of stimulatory effect.

To assess direct evidence of adrenergic stimulation in pancreatic amylase secretion, effects of catecholamines on amylase release and intracellular cyclic AMP accumulation were examined with rat dispersed pancreatic acini. We first carried out control studies with CCK-8 and carbamylcholine to evaluate the usefulness of the material for the examination of amylase secretion, and examined VIP-induced cyclic AMP accumulation to assess the agonist evoked intracellular response. As a result, significant effects of CCK-8, carbamylcholine and VIP were observed, which confirmed that dispersed pancreatic acini used in this study were useful in examining exocrine pancreatic secretion. However, catecholamines failed to stimulate amylase release from pancreatic acini, although a significant increase in intracellular cyclic AMP accumulation was observed. Thus the present study strongly suggests that direct involvement of catecholamine is unlikely in pancreatic amylase secretion, in contrast to results reported previously.     

Exocrine pancreatic secretion: effect of subarachnoidal application of cholecystokinin octapeptide in rats

Administration of cholecystokinin octapeptide (CCK-8) intravenously, or in the subarachnoidal surface of the olfactory lobe in rats, caused an increase in pancreatic protein and amylase secretion. It was observed that for subarachnoidal administration of CCK-8 both protein and amylase outputs were higher than that seen after i.v. injection. This result is consistent with the presence of central CCK receptors which when activated can enhance pancreatic exocrine secretion. The blockade of the effect of CCK by administration of CCK-8-specific antisera proves the specificity of the subarachnoidal CCK-8 stimulation.     

Reduced gastric acid inhibitory effect of a pGIP(1-30)NH2 fragment with potent pancreatic amylase inhibitory activity.

Gastric inhibitory polypeptide (GIP) strongly stimulates insulin secretion in the presence of glucose and also stimulates somatostatin release from gastric mucosa. It was reported recently that both stimulatory activities can be dissociated by removing the C-terminal 12 amino acid residues. Since insulin and somatostatin are involved in regulation of exocrine pancreatic and gastric secretion in rats, we compared the inhibitory effects of pGIP and the pGIP(1-30)NH2 fragment on pancreatic amylase and gastric acid secretion. pGIP(1-30)NH2 displayed full activity on inhibition of bombesin (BN)-stimulated amylase release relative to GIP itself, but was about 10-fold less potent in inhibiting gastric acid secretion. These results suggest that the receptors involved in these two events have quite different ligand binding requirements and that more specific analogues of GIP can be designed which should be of value in elucidating the physiological roles of this hormone.     

Effects of proglumide on pancreatic endocrine and exocrine function in healthy humans

A comparative study was done on the pancreatic endocrine (insulin (IRI), human pancreatic polypeptide (hPP] and exocrine secretion (fluid volume, amylase output, bicarbonate output), before and after administration of proglumide. At the time of the test meal loading, plasma hPP and cholecystokinin (CCK) were also measured. During continuous i.v. administration of proglumide 750 mg and 1650 mg/h 30 min before CCK-8 (20 ng/kg) stimulation, no significant difference in the rise of plasma hPP level was observed, as compared with a single stimulus of CCK-8, nor were there any significant differences in the exocrine secretion. The values of hPP and CCK-8 under a load of test meal significantly elevated after a food load. Although hPP showed a significant inhibition with the administration of proglumide 1650 mg/h, plasma CCK-8 and blood sugar levels were not significantly different from control groups. Therefore, while proglumide has a very weak effect on the action of pancreatic endocrine function, it does have an inhibitory effect on pancreatic function, during physiological stimulation.     

Amylase secretion from isolated pure acinar cells

Isolation of pure acinar cells of the rat pancreas was achieved employing counterflow sedimentation filtration technique (CSFT). The preparation of purified acinar cells contained an occasional red blood cell (RBC, 200:1) with total absence of endocrine and duct cells. A significant stimulation of amylase secretion from isolated pure acinar cells was produced by octapeptide of cholecystokinin (CCK8) and insulin produced potentiation of the effect of CCK8. Synthetic glucagon inhibited basal and CCK8 stimulated amylase secretion. Non-synthetic purified glucagon stimulated amylase secretion and potentiated the effect of CCK8. Vasoactive intestinal polypeptide (VIP) did not stimulate amylase secretion but potentiated the effect of CCK8. No leakage of lactic dehydrogenase (LDH) was detected from the cells in any of the secretion studies. Thus a highly purified preparation of isolated pure acinar cells of rat pancreas could be obtained with excellent morphologic and functional integrity.     

Involvement of cellular calcium in exocrine pancreatic insufficiency during streptozotocin-induced diabetes mellitus

This study investigates the effects of the islet hormones insulin (Ins), glucagon (Glu), and somatostatin (Som) with nerve stimulation (EFS) acetylcholine (ACh) and cholecytokinin-octapeptide (CCK-8) on amylase secretion and intracellular free calcium concentration [Ca(2+)](i) in the pancreas of age-matched control and diabetic rats. Either Ins, Glu or Som elicited small increases in amylase secretion from the pancreas of age-matched control animals compared to a much larger increase in amylase secretion with either EFS, ACh or CCK-8. Combining the islet hormones with either EFS, ACh or CCK-8 resulted in marked potentiation of amylase output. In the diabetic pancreas, the islet hormones had no effect on amylase secretion compared to diabetic control. Moreover, either EFS, ACh or CCK-8 evoked a much smaller increase in amylase output compared to age-matched control. In addition, the islet hormones failed to potentiate the secretory effects of either EFS, ACh or CCK-8. In fura-2 loaded acinar cells from age-matched control pancreas either Ins or Glu elicited a small increase in [Ca(2+)](i) whereas Som had no effect. Both ACh and CCK-8 evoked large increases in [Ca(2+)](i) compared to control. Combining either Ins, Glu or Som with either ACh or CCK-8 resulted in a marked elevation in [Ca(2+)](i) compared to the responses obtained with either the islet hormones, ACh or CCK-8 alone. In diabetic fura-2 loaded pancreatic acinar cells, the islet hormones had no effect on [Ca(2+)](i) compared to control and moreover, the responses were much smaller than those obtained in acinar cells from age-matched control. Both ACh and CCK-8 induced large increases in [Ca(2+)]( i) in diabetic acinar cells. However, combining the islet hormones with either ACh or CCK-8 failed to enhance [Ca(2+)](i) compared to the reponses obtained in acinar cells from age-matched control. The results suggests that [Ca(2+)](i) homeostasis is deranged during diabetes mellitus and this in turn is probably associated with reduced pancreatic amylase secretion.     

Effect of a new CCK-A receptor antagonist,dexloxiglumide, on the exocrine pancreas in the rat

The effect of dexloxiglumide, a new potent cholecystokinin (CCK) antagonist, on pancreatic enzyme secretion and growth was studied in the rat. Pancreatic exocrine secretion was studied both in vitro (isolated and perfused pancreatic segments) and in vivo (anaesthetized animals with cannulation of the common bile duct) whereas the trophic effect was investigated after short-term (7 days) administration of the CCK-agonist, caerulein, or camostate (a potent trypsin inhibitor), with or without dexloxiglumide. CCK-8 stimulated amylase release from in vitro pancreatic segments in a concentration-dependent manner. Dexloxiglumide displaced the concentration response curves to CCK-8 to the right without affecting the maximum response, suggesting a competitive antagonism. The Schild plot analysis of data gave a straight line with a slope (0.90±0.36) not significantly different from unity. The calculated pA₂ for dexloxiglumide was 6.41 ± 0.38. In vivo experiments confirmed results from in vitro studies since intravenous dexloxiglumide reduced pancreatic exocrine secretion induced by submaximal CCK-8 stimulation (0.5 nmol/kg/h) in a dose-dependent manner, the ID₅₀ being 0.64 mg/kg. Both exogenous and endogenous (released by camostate) CCK increased the weight of the pancreas, the total pancreatic protein and DNA, trypsin and amylase content. Dexloxiglumide (25 mg/kg), administered together with caerulein (1 μg/kg), reduced the peptide-induced increase in pancreatic weight, protein and enzyme content. Similarly, when dexloxiglumide was given together with camostate (200 mg/kg), all the observed changes were reduced by concomitant administration of the antagonist. These results demonstrate the ability of dexloxiglumide to antagonize the effects of CCK on pancreatic secretion and growth, suggesting that this compound is a potent and selective antagonist of CCK-A-receptors in the pancreas.     

Relationship of CCK/gastrin receptor binding to amylase release in dog pancreatic acini

Effects of synthetic peptides belonging to the CCK/gastrin family (CCK-39, CCK-8, G/CCK-4, G-17ns) on amylase release in dog pancreatic acini have been measured and correlated with binding of three radio-labelled CCK/gastrin peptides: ¹²⁵I-BH-(Thr,Nle)-CCK-9, ¹²⁵I-BH-(2–17)G-17ns and ¹²⁵I-BH-G/CCK-4 prepared by conjugation of the peptides to iodinated Bolton-Hunter reagent and purified by reverse-phase-HPLC. All the CCK/gastrin peptides produced the same maximal amylase release response. Half-maximal responses (D₅₀) were obtained with 2 · 10^?10 M CCK-8; 6 · 10^?10 M CCK-39; 10^?7 M G.17 ns and 2 · 10^?6 M G/CCK-4. Dose-response curves for G-17 ns and G/CCK-4 were similar in configuration but not parallel with those for CCK-8 and CCK-39.Binding studies with ¹²⁵I-BH(Thr,Nle)-CCK-9 demonstrated the presence of specific CCK receptors on dog pancreatic acini. There was a good correlation between receptor occupancy by CCK-8 and CCK-39 and amylase stimulation since maximal amylase stimulation was achieved when 40–50% of high affinity receptors were occupied. In contrast, a saturation of these receptors was required for maximal stimulation by G-17 ns and G/CCK-4 suggesting the existence of a fraction of receptors that can be occupied by G-17 ns and G/CCK-4 without stimulation of amylase release. Binding studies with labelled (2–17)-G-17 ns and G/CCK-4 confirmed the presence of high affinity sites for G-17 ns and G/CCK-4. These sites were not related to amylase release.This study points out a possible species specificity of biological action of gastrin/CCK peptides on pancreatic exocrine secretion in higher mammals.     

Effects of pancreastatin and chromogranin A on insulin release stimulated by various insulinotropic agents

The effects of porcine pancreastatin on insulin release stimulated by insulinotropic agents, glucagon, cholecystokinin-octapeptide (CCK-8), gastric inhibitory polypeptide (GIP) and L-arginine, were compared to those of bovine chromogranin A (CGA) using the isolated perfused rat pancreas. Pancreastatin significantly potentiated glucagon-stimulated insulin release (first phase: 12.5 +/- 0.9 ng/8 min; second phase: 34.5 +/- 1.6 ng/25 min in controls; 16.5 +/- 1.1 ng/8 min and 44.0 +/- 2.2 ng/25 min in pancreastatin group), whereas CGA was ineffective. The first phase of L-arginine-stimulated insulin release was also potentiated by pancreastatin (6.9 +/- 0.5 ng/5 min in controls, 8.4 +/- 0.6 ng/5 min in pancreastatin group), but not by CGA. Pancreastatin did not affect CCK-8 or GIP-stimulated insulin release. Similarly, CGA did not affect insulin release stimulated by CCK-8 or GIP. These findings suggest that pancreastatin stimulates insulin release in the presence of glucagon. Because pancreastatin can have multiple effects on insulin release, which are dependent upon the local concentration of insulin effectors, pancreastatin may participate in the fine tuning of insulin release from B cells.     

The insulin secretion of a minced neonatal rat pancreas cultured in a pancreatic chamber, in response to various insulin secretagogues

The minced pancreas of the neonatal rat was cultured for 35 days in a pancreatic chamber which was constructed of a plastic tube and an ultrafiltration membrane. Insulin and amylase secreted from this pancreatic chamber into the culture medium were measured. During the experiment, the concentration of glucose in the culture medium was changed between 5.5 and 16.5 mM at 2-3 day intervals in order to determine the insulin secretory response of the pancreatic tissue. Insulin secretion was markedly increased in response to 16.5 mM glucose. The ratio of insulin secretion to amylase secretion in the culture medium increased with the advance of culture days although secretions of both insulin and amylase decreased individually. On the 7th culture day, short term incubations were performed to test with various insulin secretagogues; obvious insulin release into the incubation medium was observed. These results show that the pancreatic chamber also in vitro secretes insulin rapidly and significantly in response to various stimuli; that by longer culture of a neonatal rat pancreas in this device, insulin secretory cells without exocrine tissue would be obtained without using digestive enzymes; that application of a pancreatic chamber for a pancreatic transplantation may be feasible.     

Relative bioactivities of cholecystokinins-8 and -33 on rat pancreatic acini

The relative potencies of cholecystokinin (CCK-33) and its carboxyl terminal octapeptide (CCK-8) for stimulation of amylase release from rat pancreatic acini was measured. Porcine CCK-33 and synthetic CCK-8 were initially subjected to high pressure liquid chromatography to assess purity. Concentrations of each peptide were determined by amino acid analysis. The relative immunoreactivities of CCK-33 and CCK-8 were compared using an antibody that recognizes the common carboxyl terminus of these forms. This antibody bound CCK-8 and CCK-33 with nearly equal affinity. The relative potencies of CCK-33 and CCK-8 were then measured by comparing their abilities to stimulate amylase release from isolated rat pancreatic acini. Statistical analysis of the relative potencies of the two hormones indicated that CCK-8 was 36% more potent than CCK-33 in this assay system. These data suggest that differences in biological activities between large and small forms of CCK are not as great as previously reported.     

The role of magnesium in regulating CCK-8-evoked secretory responses in the exocrine rat pancreas

This study investigates the effect of magnesium (Mg²⁺) on the secretory responses and the mobilization of calcium (Ca²⁺) and Mg²⁺ evoked by cholecystokinin-octapeptide (CCK-8) in the exocrine rat pancreas. In the isolated intact perfused pancreas CCK-8 (10^–10 M) produced marked increases in juice flow and total protein output in zero and normal (1.1 mM) extracellular Mg²⁺ [Mg²⁺]_o compared to a much reduced secretory response in elevated (5 mM and 10 mM) [Mg²⁺]_o Similar effects of perturbation of [Mg²⁺]_o on amylase secretion and ⁴⁵Ca²⁺ uptake (influx) were obtained in isolated pancreatic segments. In pancreatic acinar cells loaded with the fluorescent bioprobe fura-2 acetomethylester (AM), CCK-8 evoked marked increases in cytosolic free Ca²⁺ concentration [Ca²⁺]_i in zero and normal [Mg²⁺]_o compared to a much reduced response in elevated [Mg²⁺]_o Pretreatment of acinar cells with either dibutyryl cyclic AMP (DB₂ cAMP) or forskolin had no effect on the CCK-8 induced changes in [Ca²⁺]_i. In magfura-2-loaded acinar cells CCK-8 (10^–8 M) stimulated an initial transient rise in intracellular free Mg²⁺ concentration [Mg²⁺]_i followed by a more prolonged and sustained decrease. This response was abolished when sodium Na⁺ was replaced with N-methyl-D-glucamine (NMDG). Incubation of acinar cells with 10 mM Mg²⁺ resulted in an elevation in [Mg²⁺]_i. Upon stimulation with CCK-8, [Mg²⁺]_i. decreased only slightly compared with the response obtained in normal [Mg²⁺]_o. CCK-8 caused a net efflux of Mg²⁺ in pancreatic segments; this effect was abolished when extracellular sodium [Na⁺]_o was replaced with either NMDG or choline. The results indicate that Mg²⁺ can regulate CCK-8-evoked secretory responses in the exocrine pancreas possibly via Ca²⁺ mobilization. Moreover, the movement of Mg²⁺ in pancreatic acinar cells is dependent upon extracellular Na⁺.     

Vasoactive intestinal polypeptide (VIP) in the pig pancreas: role of VIPergic nerves in control of fluid and bicarbonate secretion

Vasoactive intestinal polypeptide (VIP) in the pig pancreas is localized to nerves, many of which travel along the pancreatic ducts. VIP stimulates pancreatic fluid and bicarbonate secretion like secretin. Electrical vagal stimulation in the pig causes an atropine-resistant profuse secretion of bicarbonate-rich pancreatic juice. In an isolated perfused preparation of the pig pancreas with intact vagal nerve supply, electrical vagal stimulation caused an atropine-resistant release of VIP, which accurately parallelled the exocrine secretion of juice and bicarbonate. Perfusion of the pancreas with a potent VIP-antiserum inhibited the effect of vagal stimulation on the exocrine secretion. It is concluded, that VIP is responsible for (at least part of) the neurally controlled fluid and bicarbonate secretion from the pig pancreas.     

Stimulus-specific inhibition of insulin release from rat pancreas by both rat and porcine galanin.

The effect of the neuropeptide galanin on insulin and somatostatin secretion in the rat was studied under various conditions. In the perfused rat pancreas, insulin secretion stimulated by arginine, but not cholecystokinin-8 (CCK-8) or acetylcholine (ACh) was inhibited by both rat and porcine galanin, whereas ACh-stimulated somatostatin release was inhibited by rat but not porcine galanin. Neither arginine nor CCK-8 significantly altered somatostatin secretion and galanin was without effect under those conditions. Gastric inhibitory polypeptide-stimulated insulin release from cultured mixtures of purified rat beta- and non-beta-cells was inhibited by rat and porcine galanin in a concentration-dependent and equipotent manner. The results suggest that the inhibitory effect of galanin on insulin and somatostatin secretion may be stimulus-specific and species-specific.     

Effect of acetylcholine and new cholinergic derivative on amylase output, insulin, glucagon, and somatostatin secretions from perfused isolated rat pancreas

The effect of infused acetylcholine and (2-acetyllactoyloxyethyl)-trimethylammonium hemi-1,5-naphthalenedisulfonate (aclatonium napadisilate), a new cholinergic drug . On endocrine and exocrine secretory responses was simultaneously investigated during the perfusion of isolated rat pancreases. Acetylcholine (1.1 microM) stimulated the output of pancreatic juice and amylase, and significantly elicited the production of both insulin and glucagon. Its effect on somatostatin secretion, however, was minimal. Both pancreatic juice flow and amylase output were also significantly stimulated by aclatonium napadisilate (12 microM). These stimulatory effects of aclatonium napadisilate on the exocrine pancreas were blocked by atropine (25 microM). Aclatonium napadisilate could stimulate glucagon, but could not influence insulin and somatostatin secretion. The addition of atropine had no effect on the release of insulin, glucagon, and somatostatin. These results indicate that the effects of aclatonium napadisilate is cholinergic, and that the action is muscarinic. In addition, it can be concluded that pancreatic somatostatin secretion, as well as other hormones from islet cells, is controlled by the parasympathetic nervous system.     

Interaction of caerulein, glucose, and amino acids on insulin secretion from the perfused rat pancreas

The effect of caerulein on insulin response to graded amounts of glucose from the isolated perfused rat pancreas was investigated in the presence or absence of an amino acids mixture. Caerulein at a concentration of 0.1 ng/ml which is a submaximal concentration for an effect on exocrine pancreatic secretion potentiated insulin responses to glucose concentrations less than 200 mg/dl, but produced no further increase when added to a glucose stimulus over a 200 mg/dl. However, in the presence of amino acids the insulin response to 200 mg/dl glucose was significantly potentiated by the stimulation of 0.1 ng/ml caerulein. The effectiveness of caerulein as an insulinotropic agent depended on the glucose concentration only when amino acids were present. These results indicate that caerulein, at a concentration which stimulate pancreatic exocrine secretion, has a synergistic effect on insulin response to glucose and amino acids and therefore raises the possibility that endogenously released CCK may contribute to the entero-insular axis.     

Pioglitazone reverses insulin resistance and impaired CCK-stimulated pancreatic secretion in eNOS(-/-) mice: therapy for exocrine pancreatic disorders?

In mice, eNOS (endothelial nitric oxide synthase) maintains in vivo pancreatic secretory responses to carbachol or cholecystokinin octapeptide (CCK-8), maintains insulin sensitivity, and modulates pancreatic microvascular blood flow (PMBF). eNOS(-/-) mice are insulin resistant, and their exocrine pancreatic secretion is impaired. We hypothesized that the reduced exocrine pancreatic secretion in eNOS(-/-) mice is due to insulin resistance or impaired PMBF. To test this hypothesis, we gave eNOS(-/-) and wild-type (WT) mice pioglitazone (20 or 50 mg.kg(-1).day(-1)), an insulin-sensitizing peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activator, and measured pancreatic protein secretion evoked by CCK-8 (160 pmol.kg(-1).h(-1), a maximal stimulus). We also measured insulin resistance, serum glucose, C-peptide, insulin, pancreatic RNA digestive enzyme expression, and PMBF (microsphere technique). In WT mice, pioglitazone did not increase CCK-8-stimulated protein output over baseline. In eNOS(-/-) mice, however, pioglitazone substantially increased the low CCK-8-stimulated protein output that is characteristic of these mutant mice (P < 0.005). Pioglitazone abolished the CCK-8-evoked hyperinsulinemia (P < 0.005) and increased insulin sensitivity of eNOS(-/-) mice (P < 0.05), the latter based on hyperinsulinemic-euglycemic clamp studies. Pioglitazone had no effect on PMBF or pancreas mRNA expression of insulin or digestive enzymes. We conclude that in hyperinsulinemic eNOS(-/-) mice, a nonobese model of insulin resistance relevant to diabetes mellitus and possibly chronic pancreatitis, reduced pancreatic secretion is caused, at least in part, by insulin resistance. Insulin-sensitizing PPAR-gamma agonists such as pioglitazone may thus simultaneously correct endocrine and exocrine pancreatic disorders.