Polystyrene microplastics alter the behavior, energy reserve and nutritional composition of marine jacopever (Sebastes schlegelii)

Uptake and toxicity of microplastics on marine organisms have been reported elsewhere. However, there is limited knowledge regarding the ecological effects of microplastics on marine organisms. In this study, we investigated the effects of polystyrene microplastics (1 × 10⁶ microspheres per L) on the behavior, energy reserve and nutritional composition of juvenile jacopever (Sebastes schlegelii). Compared to the controls, fish treated by microplastics showed lower sensitivity toward the added food in the tank, and increased foraging time, indicating that microplastics significantly weakened feeding activity of the fish. Interestingly, the microplastics treated-fish obviously reduced swimming speed and range of movement, demonstrating that polystyrene microplastics could have negative effect on hunting behavior. Furthermore, polystyrene microplastics accumulated in the gills and intestine, causing significant histopathological changes in the gallbladder and liver. Moreover, the energy reserve and nutritional quality of fish were influenced by microplastics as evidenced by lower growth, protein and lipid contents. Our results highlighted the potential negative effects of microplastics on marine ecological function and food safety.

Genetic analysis of digestive physiology using fluorescent phospholipid reporters

Zebrafish are a valuable model for mammalian lipid metabolism; larvae process lipids similarly through the intestine and hepatobiliary system and respond to drugs that block cholesterol synthesis in humans. After ingestion of fluorescently quenched phospholipids, endogenous lipase activity and rapid transport of cleavage products results in intense gall bladder fluorescence. Genetic screening identifies zebrafish mutants, such as fat free, that show normal digestive organ morphology but severely reduced phospholipid and cholesterol processing. Thus, fluorescent lipids provide a sensitive readout of lipid metabolism and are a powerful tool for identifying genes that mediate vertebrate digestive physiology.

Neuropeptide K: isolation, structure and biological activities of a novel brain tachykinin

A 36 amino acid residue peptide, which contains a substance K sequence at its C-terminus has been isolated from porcine brain extracts. The primary structure of the peptide, designated neuropeptide K (NPK), was found to be: (sequence; see text) This N-terminally extended form of substance K is present in a high concentration in the brain. The peptide is highly biologically active with regard to gallbladder contraction, protein extravasation, hypotension and bronchial smooth muscle spasm and may act as an additional tachykinin neuromessenger.

A potent nonpeptide cholecystokinin antagonist selective for peripheral tissues isolated from Aspergillus alliaceus

A new, competitive, nonpeptide cholecystokinin (CCK) antagonist, asperlicin, was isolated from the fungus Aspergillus alliaceus. The compound has 300 to 400 times the affinity for pancreatic, ileal, and gallbladder CCK receptors than proglumide, a standard agent of this class. Moreover, asperlicin is highly selective for peripheral CCK receptors relative to brain CCK and gastrin receptors. Since asperlicin also exhibits long-lasting CCK antagonist activity in vivo, it should provide a valuable tool for investigating the physiological and pharmacological actions of CCK.

The ultrastructural route of fluid transport in rabbit gall bladder

The route of fluid transport across the wall of the rabbit gall bladder has been examined by combined physiological and morphological techniques. Fluid transport was either made maximal or was inhibited by one of six physiological methods (metabolic inhibition with cyanide-iodoacetate, addition of ouabain, application of adverse osmotic gradients, low temperature, replacement of Cl by SO(4), or replacement of NaCl by sucrose). Then the organ was rapidly fixed and subsequently embedded, sectioned, and examined by light and electron microscopy. The structure of the gall bladder is presented with the aid of electron micrographs, and changes in structure are described and quantitated. The most significant morphological feature seems to be long, narrow, complex channels between adjacent epithelial cells; these spaces are closed by tight junctions at the luminal surface of the epithelium but are open at the basal surface. They are dilated when maximal fluid transport occurs, but are collapsed under all the conditions which inhibit transport. Additional observations and experiments make it possible to conclude that this dilation is the result of fluid transport through the spaces. Evidently NaCl is constantly pumped from the epithelial cells into the spaces, making them hypertonic, so that water follows osmotically. It is suggested that these spaces may represent a "standing-gradient flow system," in which osmotic equilibration takes place progressively along the length of a long channel.

Effects of pregnancy and contraceptive steroids on gallbladder function

We used real-time ultrasonography to study gallbladder kinetics in 11 nonpregnant women, 17 women using steroid contraceptives, and 33 pregnant women. Gallbladder volume was determined after an overnight fast and serially for 90 minutes after a standard liquid meal. After the first trimester of pregnancy, gallbladder volume during fasting and residual volume after contraction were twice as large as in control subjects. The rate of emptying and the percentage emptied were reduced. In early pregnancy the only important abnormality was a 30 per cent decrease in emptying rate. Gallbladder function was not affected by contraceptive steroids. Incomplete empyting of the gallbladder in late pregnancy leaves a large residual volume and may cause retention of cholesterol crystals, a prerequisite for cholesterol-gallstone formation. These findings are consistent with the view that pregnancy increases the risk of cholesterol gallstones. The increased incidence of gallstones associated with contraceptive steroids does not involve abnormal gallbladder kinetics.

Silymarin retards collagen accumulation in early and advanced biliary fibrosis secondary to complete bile duct obliteration in rats

Silymarin (SIL), a standardized plant extract containing about 60% polyphenole silibinin, is used as a hepatoprotective agent. Its antifibrotic potential in chronic liver diseases has not been explored. Therefore, we applied SIL to adult Wistar rats that were subjected to complete bile duct occlusion (BDO) by injection of sodium amidotrizoate (Ethibloc). This treatment induces progressive portal fibrosis without significant inflammation. Rats with sham-operation that received SIL at 50 mg/kg/d (n = 10) and rats with BDO alone (n = 20) served as controls, whereas groups of 20 animals were fed SIL at a dose of 25 and 50 mg/kg/d during weeks 1 through 6 or doses of 50 mg/kg/d during weeks 4 through 6 of BDO. Animals were sacrificed after 6 weeks for determination of blood chemistries, total and relative liver collagen (as hydroxyproline [HYP]), and the serum aminoterminal propeptide of procollagen type III (PIIINP). BDO in untreated rats caused an almost ninefold increase in total liver collagen (16.1 +/- 3.1 vs. 1.8 +/- 0.4 mg HYP, P < .001). SIL at 50 mg/kg/d reduced total HYP by 30% to 35%, either when given from week 1 through 6 or from week 4 through 6 after BDO (10.6 +/- 2.7 and 10.2 +/- 3.9 mg HYP, both P < .01 vs. BDO alone), whereas 25 mg/kg/d were ineffective. Because SIL at 50 mg/kg/d also reduced the collagen content per gram of liver tissue, it acted as a true antifibrotic agent. The single value of PIIINP at killing paralleled the antifibrotic activity of SIL with 11.6 +/- 3.8 and 9.9 +/- 3.7 vs. 15.3 +/- 5.2 microg/L in both high-dose groups (P < .05 and P < .01, respectively, vs. rats with BDO alone). Except for a decreased alkaline phosphatase and a lower histological fibrosis score in the groups that received SIL, clinical-chemical parameters were not different among all groups with BDO. We therefore conclude that 1) BDO with Ethibloc is a suitable model to test for pure antifibrotic drugs because it induces progressive rat secondary biliary fibrosis without major inflammation; 2) oral SIL can ameliorate hepatic collagen accumulation even in advanced (biliary) fibrosis; and 3) PIIINP appears to be a suitable serum marker to monitor the inhibition of hepatic fibrogenesis in this model of biliary fibrosis.

Fatty acid chain length determines cholecystokinin secretion and effect on human gastric motility

BACKGROUND & AIMS

Fatty acids induce cholecystokinin (CCK) secretion and modify gastric motility, but the chain length requirements for these effects are not known. Nor is it clear whether the effects of fatty acids on gastric motility in humans are CCK mediated or directly exerted. The aim of this study was to determine the role of fatty acyl chain length in CCK secretion and in influencing gastric motility.

METHODS

Fatty acids were infused into the upper gut in healthy volunteers; plasma CCK was determined by radioimmunoassay. Effects of fatty acids on antral contractility were determined by percutaneous ultrasonography; effects on proximal gastric tone were studied during fundal distention.

RESULTS

Plasma CCK concentration was consistently and similarly elevated by fatty acids with a chain of 12 carbon atoms or longer, whereas those of 11 or fewer carbon atoms failed to increase plasma CCK. A 12-carbon but not a 10-carbon-long chain fatty acid reduced antral contractile amplitude, an effect that was abolished by loxiglumide (a specific CCK-A receptor antagonist). The 12-carbon fatty acid also reduced proximal gastric tone more than the 10-carbon fatty acid.

CONCLUSIONS

A highly specific, chain length-sensitive fatty acid recognition system exists in the proximal gut mediating CCK secretion and gastric motility. An additional, probably CCK-independent, effect of fatty acid also regulates proximal gastric tone.

Expression of ABCG5 and ABCG8 is required for regulation of biliary cholesterol secretion

The major pathway for elimination of cholesterol in mammals is via secretion into bile. Biliary cholesterol secretion is mediated by the ATP-binding cassette (ABC) transporters ABCG5 (G5) and ABCG8 (G8) and is stimulated by cholesterol and by the non-cholesterol steroids cholate and diosgenin. To define the relationship between G5G8 expression and biliary cholesterol secretion, we measured G5 and G8 mRNA levels and biliary cholesterol concentrations in genetically manipulated mice expressing 0, 1, 2, 5, 10, or 16 copies of the two genes. Biliary cholesterol levels varied directly with G5G8 copy number and hepatic mRNA levels over a >16-fold range. Thus neither delivery of cholesterol to the transporter nor levels of cholesterol acceptors in bile were limiting under these conditions. In wild-type mice, cholate and diosgenin both increased biliary cholesterol concentrations 2-3-fold. The increase in biliary cholesterol content was dependent on expression of G5 and G8; neither steroid increased biliary cholesterol levels in G5G8-/- mice. Cholate treatment was associated with a farnesoid X receptor (FXR)-dependent increase in hepatic mRNA and protein levels of G5 and G8. In contrast to cholate, diosgenin treatment did not affect G5G8 expression. Diosgenin increased the expression of several pregnane X receptor (PXR) target genes and the choleretic effect of diosgenin was reduced by approximately 70% in PXR knock-out mice. Thus G5 and G8 are required to modulate biliary cholesterol secretion in response to cholate and diosgenin, but the choleretic effects of these two steroids are mediated by different mechanisms requiring FXR and PXR, respectively.

Mechanisms of gallstone formation in women. Effects of exogenous estrogen (Premarin) and dietary cholesterol on hepatic lipid metabolism

Our aim was to define mechanisms whereby conjugated estrogens (Premarin, exogenous estrogen; Ayerst Laboratories, New York) increase the risk of developing cholesterol gallstones and to determine the role, if any, of dietary cholesterol. We studied gallbladder motor function, biliary lipid composition and secretion, cholesterol absorption, cholesterol synthesis and esterification by peripheral blood mononuclear cells, the clearance of chylomicron remnants, and bile acid kinetics in 29 anovulatory women. 13 were studied on both a low (443 +/- 119 mumol/d) and high (2,021 +/- 262 mumol/d) cholesterol diet. Premarin increased the lithogenic index of bile (P less than 0.05), increased biliary cholesterol secretion (P less than 0.005), lowered chenodeoxycholate (CDCA) pool (P less than 0.001) and synthesis (P less than 0.05), altered biliary bile acid composition [( CA + DCA]/CDCA increases, P less than 0.005), stimulated cholesterol esterification (P less than 0.03), and enhanced the clearance of chylomicron remnants (P = 0.07). Increases in dietary cholesterol stimulated the biliary secretion of cholesterol (P = 0.07), bile acid (P less than 0.05), phospholipid (P = 0.07), and as a result, did not alter lithogenic index. The reduction in CDCA pool and synthesis by Premarin was reversed by increasing dietary cholesterol. Off Premarin, only 24% of the increase in cholesterol entering the body in the diet was recovered as biliary cholesterol or newly synthesized bile acid. On Premarin, 68% of this increase in cholesterol was recovered as these biliary lipids. We conclude that Premarin increases biliary cholesterol by enhancing hepatic lipoprotein uptake and inhibiting bile acid synthesis. These actions of Premarin divert dietary cholesterol into bile.

Effect of loss of P2Y(2) receptor gene expression on nucleotide regulation of murine epithelial Cl(-) transport

Extracellular nucleotides are believed to be important regulators of ion transport in epithelial tissues as a result of their ability to activate cell surface receptors. Although numerous receptors that bind nucleotides have been identified, the complexity of this receptor family, combined with the lack of pharmacological agents specific for these receptors, has made the assignment of particular receptors and ligands to physiological responses difficult. Because ATP and UTP appear equipotent and equieffective in regulating ion transport in many epithelia, we tested the hypothesis that the P2Y(2) receptor (P2Y(2)-R) subtype mediates these responses in mouse epithelia, with gene targeting techniques. Mice with the P2Y(2)-R locus targeted and inactivated (P2Y(2)-R(-/-)) were generated, airways (trachea), gallbladder, and intestines (jejunum) excised, and Cl(-) secretory responses to luminal nucleotide additions measured in Ussing chambers. Comparison of P2Y(2)-R(+/+) with P2Y(2)-R(-/-) mice revealed that P2Y(2)-R mediated most (>85-95%) nucleotide-stimulated Cl(-) secretion in trachea, about 50% of nucleotide responses in the gallbladder, and none of the responses in the jejunum. Dose-effect relationships for nucleotides in tissues from P2Y(2)-R(-/-) mice suggest that the P2Y(6)-R regulates ion transport in gallbladder and to a lesser extent trachea, whereas P2Y(4) and/or unidentified receptor(s) regulate ion transport in jejunum. We conclude that the P2Y(2) receptor is the dominant P2Y purinoceptor that regulates airway epithelial ion transport, whereas other P2Y receptor subtypes are relatively more important in other nonrespiratory epithelia.

Inhibition of pancreas and gallbladder by pancreatic polypeptide

Stimulated pancreatic and biliary outputs were studied in seven healthy subjects during intravenous infusion of bovine pancreatic polypeptide (P.P.) (mean dose 65 pmol/kg/h). P.P. significantly inhibited outputs of trypsin and bilirubin at plasma concentrations similar to those observed after meals. In four cholecystectomised subjects, P.P. inhibited only trypsin output.

Involvement of calcium and cytoskeleton in gallbladder epithelial cell volume regulation

The importance of calcium and cellular cytoskeletal elements in the activation or control of volume regulation by epithelial cells was explored in Necturus gallbladder. Gallbladder cells have been previously shown to rapidly readjust their volumes to control size after osmotic perturbation of the mucosal bathing solution. Removal of calcium from the perfusates caused dramatic morphological changes that prevented assessment of the role of extracellular calcium in volume regulation. The regulatory volume increase (RVI) that follows shrinkage of the cell due to perfusion of a hypertonic mannitol solution is insensitive to agents that interfere with cell calcium- or calmodulin-mediated events (quinidine, trifluoperazine) and is not blocked by agents that cause changes in the cytoskeleton (colchicine, cytochalasin B). Osmotically induced cell swelling is followed by regulatory volume decrease (RVD), which is inhibited by agents that interfere with calcium-dependent processes (quinidine, trifluoperazine) and by the microfilament inhibitor, cytochalasin B. These results indicate that RVD depends on calcium, calmodulin, and an intact microfilament network, whereas RVI is independent of these factors.

Effect of cholecystokinin and the octapeptide of cholecystokinin on the feline sphincter of Oddi and gallbladder. Mechanisms of action

We studied the effect of cholecystokinin (CCK) and the octapeptide of cholecystokinin (OP-CCK) on the feline gallbladder and sphinecter of Oddi. Both CCK caused a dose-dependent gallbladder contraction and sphincter of Oddi relaxation. The half-maximal responses of the sphincter of Oddi were 6 ng/kg for OP-CCK and 0.15 Ivy-dog U/kg for CCK, which were lower than those of the gallbladder with 28 ng/kg and 0.32 Ivy-dog U/kg, respectively. The effect of OP-CCK on the gallbladder was partially blocked by tetrodotoxin (P < 0.02), hexamethonium alone (P < 0.05), or a combination of hexamethonium and atropine (P < 0.01). The gallbladder response to CCK was not blocked by either atropine alone (P < 0.60) or adrenergic antagonists (P > 0.40). The sphincter of Oddi response to OP-CCK was blocked by tetrodotoxin (P < 0.001) but it was not blocked by cholinergic (P < 0.20) or adrenergic antagonists (P < 0.60). After complete denervation with tetrodotoxin, OP-CCK caused sphincter of Oddi contraction. These findings indicate that there are two excitatory receptors for CCK in the gallbladder, one at the cholinergic neurons and the other at the level of the gallbladder muscle. There are also two receptors for CCK in the sphincter of Oddi, one that is inhibitory, and present at the noncholinergic, nonadrenergic neurons, and the other, excitatory, at the circular muscle.

Safety of Semaglutide

The glucagon-like peptide-1 receptor agonist (GLP-1RA) semaglutide is the most recently approved agent of this drug class, and the only GLP-1RA currently available as both subcutaneous and oral formulation. While GLP-1RAs effectively improve glycemic control and cause weight loss, potential safety concerns have arisen over the years. For semaglutide, such concerns have been addressed in the extensive phase 3 registration trials including cardiovascular outcome trials for both subcutaneous (SUSTAIN: Semaglutide Unabated Sustainability in Treatment of Type 2 Diabetes) and oral (PIONEER: Peptide InnOvatioN for the Early diabEtes tReatment) semaglutide and are being studied in further trials and registries, including real world data studies. In the current review we discuss the occurrence of adverse events associated with semaglutide focusing on hypoglycemia, gastrointestinal side effects, pancreatic safety (pancreatitis and pancreatic cancer), thyroid cancer, gallbladder events, cardiovascular aspects, acute kidney injury, diabetic retinopathy (DRP) complications and injection-site and allergic reactions and where available, we highlight potential underlying mechanisms. Furthermore, we discuss whether effects are specific for semaglutide or a class effect. We conclude that semaglutide induces mostly mild-to-moderate and transient gastrointestinal disturbances and increases the risk of biliary disease (cholelithiasis). No unexpected safety issues have arisen to date, and the established safety profile for semaglutide is similar to that of other GLP-1RAs where definitive conclusions for pancreatic and thyroid cancer cannot be drawn at this point due to low incidence of these conditions. Due to its potent glucose-lowering effect, patients at risk for deterioration of existing DRP should be carefully monitored if treated with semaglutide, particularly if also treated with insulin. Given the beneficial metabolic and cardiovascular actions of semaglutide, and the low risk for severe adverse events, semaglutide has an overall favorable risk/benefit profile for patient with type 2 diabetes.

Preparation of highly active enterogastrone

By using a 10% pure preparation of cholecystokinin–pancreozymin (CCK–PZ) a fraction was obtained which was inhibitory for H+ secretion, pepsin secretion, and motor activity in antral and fundic pouches. This material possessed no significant CCK–PZ activity or secretin-like activity.

Regulation of Human Adipose Tissue Activation, Gallbladder Size, and Bile Acid Metabolism by a β3-Adrenergic Receptor Agonist

β3-adrenergic receptor (AR) agonists are approved to treat only overactive bladder. However, rodent studies suggest that these drugs could have other beneficial effects on human metabolism. We performed tissue receptor profiling and showed that the human β3-AR mRNA is also highly expressed in gallbladder and brown adipose tissue (BAT). We next studied the clinical implications of this distribution in 12 healthy men given one-time randomized doses of placebo, the approved dose of 50 mg, and 200 mg of the β3-AR agonist mirabegron. There was a more-than-dose-proportional increase in BAT metabolic activity as measured by [18F]-2-fluoro-D-2-deoxy-d-glucose positron emission tomography/computed tomography (medians 0.0 vs. 18.2 vs. 305.6 mL ⋅ mean standardized uptake value [SUVmean] ⋅ g/mL). Only the 200-mg dose elevated both nonesterified fatty acids (68%) and resting energy expenditure (5.8%). Previously undescribed increases in gallbladder size (35%) and reductions in conjugated bile acids were also discovered. Therefore, besides urinary bladder relaxation, the human β3-AR contributes to white adipose tissue lipolysis, BAT thermogenesis, gallbladder relaxation, and bile acid metabolism. This physiology should be considered in the development of more selective β3-AR agonists to treat obesity-related complications.

The in vitro pharmacological profile of prucalopride, a novel enterokinetic compound

Prucalopride is a novel enterokinetic compound and is the first representative of the benzofuran class. We set out to establish its pharmacological profile in various receptor binding and organ bath experiments. Receptor binding data have demonstrated prucalopride's high affinity to both investigated 5-HT(4) receptor isoforms, with mean pK(i) estimates of 8.60 and 8.10 for the human 5-HT(4a) and 5-HT(4b) receptor, respectively. From the 50 other binding assays investigated in this study only the human D(4) receptor (pK(i) 5.63), the mouse 5-HT(3) receptor (pK(i) 5.41) and the human sigma(1) (pK(i) 5.43) have shown measurable affinity, resulting in at least 290-fold selectivity for the 5-HT(4) receptor. Classical organ bath experiments were done using isolated tissues from the rat, guinea-pig and dog gastrointestinal tract, using various protocols. Prucalopride was a 5-HT(4) receptor agonist in the guinea-pig colon, as it induced contractions (pEC(50)=7.48+/-0.06; insensitive to a 5-HT(2A) or 5-HT(3) receptor antagonist, but inhibited by a 5-HT(4) receptor antagonist) as well as the facilitation of electrical stimulation-induced noncholinergic contractions (blocked by a 5-HT(4) receptor antagonist). Furthermore, it caused relaxation of a rat oesophagus preparation (pEC(50)=7.81+/-0.17), in a 5-HT(4) receptor antagonist sensitive manner. Prucalopride did not cause relevant inhibition of 5-HT(2A), 5-HT(2B), or 5-HT(3), motilin or cholecystokinin (CCK(1)) receptor-mediated contractions, nor nicotinic or muscarinic acetylcholine receptor-mediated contractions, up to 10 microM. It is concluded that prucalopride is a potent, selective and specific 5-HT(4) receptor agonist. As it is intended for treatment of intestinal motility disorders, it is important to note that prucalopride is devoid of anti-cholinergic, anticholinesterase or nonspecific inhibitory activity and does not antagonise 5-HT(2A), 5-HT(2B) and 5-HT(3) receptors or motilin or CCK(1) receptors.

Effects of a novel cholecystokinin (CCK) receptor antagonist, MK-329, on gallbladder contraction and gastric emptying in humans. Implications for the physiology of CCK

To explore the physiology of cholecystokinin (CCK) in humans, we investigated the effect on gallbladder contraction and gastric emptying of a recently developed CCK receptor antagonist, MK-329. In a double-blind, four-period crossover study eight subjects received single doses of 0.5, 2, or 10 mg MK-329, or placebo, followed by an intravenous infusion of CCK-8 (30 pmol/kg.h). In placebo-treated subjects gallbladder volumes decreased on average to 43% of initial volumes after 2 h of CCK infusion. MK-329 caused a dose-dependent inhibition of CCK-stimulated gallbladder contraction with 10 mg producing complete blockade (P less than 0.01, cf. placebo). Gallbladder contraction and gastric emptying rates after a mixed meal were then measured in a two-period crossover study. Subjects received placebo or 10 mg of MK-329 2 h before eating. Gastric emptying of both solids and liquids was measured simultaneously by gamma scintigraphy. In placebo-treated subjects plasma CCK levels increased postprandially to 2.3 pM, gallbladder volumes decreased 68.4 +/- 3.8% (SE), and the times for 50% emptying of liquids and solids from the stomach were 58 +/- 10 and 128 +/- 8 min, respectively. In MK-329-treated subjects there was a marked elevation in peak CCK levels to 13.8 pM (P less than 0.01, cf. placebo), and gallbladder contraction was completely inhibited. Solid and liquid emptying rates were unaffected. These findings demonstrate that (a) MK-329 is a potent, orally active antagonist of CCK in humans, and (b) CCK is the major regulator of postprandial gallbladder contraction. These data also support the concept of negative feedback regulation of CCK secretion and suggest that mechanisms other than CCK play a dominant role in the regulation of postprandial gastric emptying rates.

Relative potency of bombesin-like peptides

The pharmacological activity of two natural bombesin-like peptides, alytesin and litorin, and 25 related synthetic peptides has been compared to that of bombesin. 2 The minimum length of the amino acid chain required for the first appearance of bombesin-like effects was represented by the C-terminal heptapeptide, and the minimum length for maximal effects by the C-terminal nonapeptide. The latter possessed approximately the same activity as bombesin and may be considered a good substitute. 3 Both the tryptophan and histidine residues seemed to be essential for bombesin-like activity. 4 The C-terminal octapeptide was less active than either bombesin or the C-terminal nonapeptide and its action was more rapid in onset and less sustained. 5 Litorin apparently has an intermediate position between bombesin octapeptide and bombesin nonapeptide in the speed and duration of its effects. The relationship between structure and activity is discussed.

Cholelitholysis using methyl tertiary butyl ether

We tested methyl tertiary butyl ether both in vitro and in vivo to evaluate its efficacy as a potential cholesterol gallstone solvent for direct instillation into the human gallbladder or bile duct. Like diethyl ether, methyl tertiary butyl ether is an aliphatic ether with an excellent cholesterol-solubilizing capacity. However, unlike diethyl ether which vaporizes at body temperature, methyl tertiary butyl ether remains a liquid having a boiling point of 55.2 degrees C. In vitro, methyl tertiary butyl ether dissolved human gallstones (40%-94% cholesterol) within 60-100 min. In contrast, monooctanoin, an established gallstone solvent, required greater than 50 h to dissolve similar stones. By direct catheter instillation in 6 dogs, methyl tertiary butyl ether required only 4-16 h to dissolve gallstones surgically implanted in the gallbladder. The dogs tolerated methyl tertiary butyl ether with only minor clinical, biochemical, or histologic effects. We conclude that further evaluation of methyl tertiary butyl ether for dissolution of human gallbladder and biliary duct cholesterol stones is warranted.

Evidence of cholecystokinin release by bombesin in the dog

1 The intravenous infusion of bombesin elicited in the dog a contraction of the gall bladder with decreased opening pressure of the choledocho-duodenal junction and stimulation of pancreatic secretion.2 The pancreatic juice produced under the influence of bombesin was poor in bicarbonate and rich in protein. Threshold doses of the peptide were of the order of 0.25 mug kg(-1) h(-1) and maximum protein output was obtained with 1 mug kg(-1) h(-1). The pancreatic protein response to bombesin was very similar, in its onset and duration, to that elicited by intraduodenal infusion of L-tryptophan. Infusions of bombesin repeated at short intervals produced tachyphylaxis.3 Antrectomy did not affect the stimulant action of bombesin on the pancreas. Atropine however, reduced the pancreatic protein response to bombesin.4 It is suggested that bombesin acts on the gall bladder and the exocrine pancreas through release of cholecystokinin from the duodenal mucosa. No release of secretion could be demonstrated. It is likely that the releasing activity of bombesin is limited, in the field of gastrointestinal peptides, to those belonging to the gastrin-cholecystokinin family.

Long-term therapy with long-acting octreotide (Sandostatin-LAR) for the management of acromegaly

OBJECTIVES

To evaluate the efficacy and safety of a long-acting preparation of the somatostatin analogue octreotide, Sandostatin-LAR (SMS-LAR) for the treatment of acromegaly.

DESIGN AND PATIENTS

Thirteen patients with acromegaly received intramuscular injections of SMS-LAR 20-40 mg at 4-6 week intervals for a period of up to 3 years.

MEASUREMENTS

Serial measurement of serum GH and IGF concentrations were obtained. Symptoms related to acromegaly were scored by patients at baseline and following each injection. Serial gallbladder ultrasound and pituitary imaging was performed throughout the study.

RESULTS

One patient was withdrawn from the study after 6 months because of continued gastrointestinal side effects; 4 patients were treated with monthly injections for 12 months and 8 patients with injections at either 1 month or 6-week intervals for 36 months; hence data is presented for n = 12 for up to 12 months; and thereafter n = 8. SMS-LAR significantly reduced serum GH and IGF-1 values: for the whole group GH concentrations fell from 24.8 +/- 4.2 mU/l (mean +/- SE) at baseline to 5.2 +/- 0.8 mU/l at 12 months (P < 0.01, n = 12). In the 8 patients treated for 3 years GH fell from 27.8 +/- 6.1 mU/l at baseline to 4.2 +/- 0.8 mU/l at the end of 3 years (P < 0.01, n = 8). GH fell to < 10 mU/l in all subjects and was < 5 mU/l in 50% after both 1 and 3 years. IGF-1 concentrations fell from 95 +/- 13 nmol/l at baseline to 63 +/- 13 nmol/l after 1 year (P < 0.01, n = 12; reference range < 65 nmol/l). In the 8 patients treated for 3 years IGF-1 concentrations fell from 119 +/- 14 nmol/l at baseline to 60 +/- 13 nmol/l after 3 years (P < 0.001, n = 8). IGF-1 was < 65 nmol/l in 60% of patients after 1 year and 75% after 3 years. Treatment resulted in trends towards improvement in symptoms of acromegaly and statistically significant improvement in sweating. There was no evidence of tachyphylaxis or evidence to suggest development of glucose intolerance. Only 2 patients (15%) developed gallbladder sludge which was asymptomatic; no patient developed gallstones.

CONCLUSIONS

We conclude that SMS-LAR is a safe, effective and well tolerated treatment, making it an important therapeutic option in the management of acromegaly.