Release of neurotensin by selective perfusion of the jejunum with oleic acid in dogs

Plasma neurotensin concentrations are rapidly elevated after oral ingestion or intraduodenal infusion of fat, apparently before fat reaches the ileum where neurotensin is highly concentrated. The purpose of this study was to investigate the site of neurotensin release and to determine whether neurotensin is released by direct luminal stimulation by fat in conscious dogs. Dogs were prepared with isolated jejunal or ileal segments and portal vein catheters. Release of neurotensin into the portal venous blood was examined by selective perfusion of each intestinal segment with sodium oleáte. The results of this study show that selective perfusion of the jejunum, but not the ileum, with sodium oleate, caused a significant release of neurotensin. We speculate that release of ileal neurotensin is not due to direct luminal stimulation, but is mediated by local neural or humoral intermediates.

Effect of pancreastatin on pancreatic endocrine and exocrine secretion

Pancreastatin is a novel peptide that was recently purified from extracts of the porcine pancreas. The present study shows that pancreastatin (10(-9)-10(-8) M) can stimulate release of insulin from both the isolated perfused rat pancreas and from cultured rat islet cells in the presence of a low, non-insulinotropic concentration of glucose (4.2 mM). Pancreastatin (10(-9) M) can also inhibit release of insulin stimulated by a high concentration of glucose (16.7 mM). Pancreastatin, at 10(-8) M, can enhance glucose (8.3 mM) induced release of insulin in the static islet cell incubation. In addition, pancreastatin (10(-9)-10(-8) M) can inhibit, in a dose-dependent fashion, cholecystokinin (CCK)-8 stimulated release of amylase from dispersed guinea pig pancreatic acini. Pancreastatin alone, however, did not affect basal release of amylase. Our study shows that pancreastatin can exert a direct effect on both pancreatic endocrine and exocrine secretion.

Parathyroid hormone-related protein relaxes rat gastric smooth muscle and shows cross-desensitization with parathyroid hormone

Previously, we reported that parathyroid hormone (PTH) is a potent and effective relaxant of rat gastrointestinal smooth muscle. Since the recently discovered PTH-related protein (PTHrP) has amino-terminal homology with PTH and acts like PTH on bone and kidney, we decided to study the effects of synthetic PTHrP analogs on the isometric tension of rat fundic strips. Rat (r) PTH-(1-34), human (h) PTHrP-(1-34), and [Tyr0]hPTHrP-(1-34) relaxed acetylcholine-stimulated fundic strips in a dose-dependent manner, with an IC50 of 6, 10, and 31 nM, respectively. However, maximal doses of [Tyr0]hPTHrP-(1-34) were considerably less effective than the other two peptides. Addition of rPTH-(1-34) or hPTHrP-(1-34) to a maximally effective dose of [Tyr0]hPTHrP-(1-34) produced no further relaxation, indicating that [Tyr0]hPTHrP-(1-34) also has antagonistic properties. Bovine PTH-(3-34) an established in vitro antagonist of PTH, partially inhibited the relaxant effect of PTHrP. Fundic strips that had been desensitized by preincubation for 30-45 minutes with either rPTH-(1-34) or hPTHrP-(1-34) (330-500 nM) were also insensitive to the relaxant action of either peptide, but in the same preparations, the relaxation produced by vasoactive intestinal peptide was unaffected. These studies indicate that PTHrP and PTH can interact with the same receptor. Whether PTHrP influences gastrointestinal motility in normal or tumor-bearing persons remains to be investigated.

Contractile response of canine gallbladder and sphincter of Oddi to substance P and related peptides in vitro

Substance P (SP) is a neurotransmitter peptide that is widely distributed in the body. Since SP has been demonstrated in the gallbladder (GB) and bile ducts of dogs, it may have a role in biliary motility. The objective of this study was to examine the effect of SP on the GB and sphincter of Oddi (SOD) of dogs in vitro, to evaluate the structure-activity relationship of SP, and to compare the contractile effect of SP with that of cholecystokinin octapeptide (CCK-8) and acetylcholine (Ach). Isolated longitudinal strips of GB and SOD from dogs were suspended in oxygenated Krebs buffer and the isometric tension responses to various doses of CCK-8, Ach, SP, and SP homologs [SP-free acid (SPFA), Octa-SP (O-SP), physalaemin (PHY)] were measured. We found that all the SP homologs, other than SPFA, stimulated GB and SOD contractions in vitro in a dose-dependent manner. The potency of SP and its homologs on GB and SOD was SP greater than or equal to PHY greater than O-SP; SPFA was without effect. CCK-8 was significantly more effective than SP on GB contraction, but unlike SP, CCK had no effect on SOD. The maximum contraction achieved by Ach was 1.3 (SOD) to 2.3 (GB) times greater than that achieved by SP, but the ED50 of SP was approximately 100- to 200-fold lower than that of Ach. The contractile effect of SP was partially blocked by 10(-5) M atropine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreatic secretion and the release of cholecystokinin after a meal in dogs with and without exclusion of pancreatic juice

Pancreatic secretion and plasma levels of cholecystokinin-33/39 (CCK) were measured for 5 h after a meal in dogs with and without exclusion of pancreatic juice. Significant and prolonged increases in pancreatic secretion and plasma CCK levels were observed irrespective of pancreatic juice exclusion. The integrated responses of pancreatic protein output (2.6 +/- 0.6 g/300 min), plasma CCK (1.3 +/- 0.5 nmol.l-1 .300 min) with exclusion of pancreatic juice showed no significant differences from those without exclusion (2.8 +/- 0.3 g/300 min and 1.3 +/- 0.3 nmol.l-1.300 min for protein output and CCK, respectively). These results suggest that the CCK-mediated feedback mechanism of pancreatic enzyme secretion does not work, at least not in the postprandial state in dogs.

Preoperative endoscopic retrograde cholangiopancreatography (ERCP) in patients with pancreatic pseudocyst associated with resolving acute and chronic pancreatitis

Experience with patients with pancreatic pseudocysts has led the authors to the hypothesis that preoperative evaluation of the pancreatic and bile ducts by ERCP will define those patients who may be inadequately treated by pseudocyst drainage alone without attention to associated pancreatic and biliary ductal abnormalities. In patients with certain ductal abnormalities, the pseudocyst operation was combined with a definitive operative drainage of the pancreatic duct and/or of the biliary tree where appropriate. A prospective evaluation of routine preoperative ERCP was undertaken over a 36-month period in all patients scheduled for operative treatment of pseudocyst of the pancreas. From an initial group of 44 patients with pseudocysts, three patients who had spontaneous regression of the pseudocyst were excluded. ERCP was successful in 39 of the remaining 41 patients. Among 41 operated patients, 24 were admitted with a diagnosis of pseudocyst that arose after an episode of acute pancreatitis, and 17 had chronic pancreatitis with pseudocyst. Nine patients, initially assumed to have acute pancreatitis, were recognized to have chronic pancreatitis on the basis of ERCP findings. Communication with the main pancreatic duct (MPD) was demonstrated in 18 of 41 pseudocysts, and the rate of communication was similar in patients with acute and chronic pancreatitis. Dilatation of the MPD was seen in 23 of 41 patients and was associated with chronic pancreatitis in 21. Dilatation of the common bile duct was found in 12 patients with chronic pancreatitis. The operative plan was altered by ERCP findings in 24 of 41 patients; 22 of the 24 patients had chronic pancreatitis. There were no complications of ERCP. These data suggest that ERCP should be performed in all patients with pseudocysts to establish correct diagnosis and to allow optimal choice of operation.

Effect of galanin on glucose-, arginine-, or potassium-stimulated insulin release

We have examined the effect of galanin infusion on glucose-stimulated release of insulin from the isolated perfused pancreas of the rat to better characterize the effect of galanin on the first and second phases of insulin release. The effects of galanin on insulin release stimulated by L-arginine or high concentrations of potassium were also examined. When perfusion of galanin was started 4 min before the start of perfusion of high glucose (16.7 mM), galanin (10(-8)-10(-11) M) inhibited both the first and second phases of insulin release in a dose-dependent manner. When perfusion of galanin (10(-8) or 10(-9) M) was started simultaneously with high glucose (16.7 mM), only the second phase of insulin release was suppressed (P less than 0.05). Galanin (10(-9) M) failed to inhibit insulin release stimulated by L-arginine (10 and 5 mM) or potassium (25 and 20 mM). These findings suggest that the inhibitory action of galanin on glucose-stimulated insulin release is exerted on early intracellular events that occur during the stimulation of insulin release and that are common to both phases. Because galanin does not inhibit insulin release stimulated by L-arginine or potassium, galanin may inhibit glucose-stimulated closure of potassium channels.

Intracerebroventricular administration of bombesin inhibits biliary and gastric secretion in the rat

The effect of intracerebroventricular (ICV) bombesin on bile and gastric acid secretion was examined in the rat. ICV bombesin (10 micrograms in 10 microliters) inhibited basal biliary volume by 27% and bile bicarbonate by 52% of control values, while gastric acid secretion was decreased by 75%. These results provide evidence for central mechanisms for the control of gastrointestinal function.

An unusual Heinz body anaemia in a cat

A severe anaemia was diagnosed in a 7-month-old female cat. Most erythrocytes contained unusually large Heinz bodies and showed marked distortion. Six weeks later, the cat had recovered from the anaemia, but the erythrocytes still contained smaller inclusions. By light microscopy, these inclusions did not stain as typical Heinz bodies, but, by electron microscopy, Heinz bodies and autophagocytic vacuoles were identified. It is suggested that this cat had a pre-existing defect in its haemoglobin which made it more susceptible to damage by an unknown oxidizing agent.

Peptide YY inhibits the insulinotropic action of gastric inhibitory polypeptide

Peptide YY (PYY) is released from the gut after ingestion of fat or after a meal. The purpose of this investigation was to examine the effect of PYY on gastric inhibitory polypeptide (GIP)-stimulated insulin release in conscious dogs with gastric and duodenal fistulas. In control experiments, 6 dogs received GIP (400 pmol/kg, i.v., for 1 h) and glucose (0.6 g/kg, i.v., for 1 h); the integrated insulin response over a 1-h period was 142 +/- 32.7 ng-60 min/ml. The plasma GIP levels achieved by this procedure were similar to those observed by intraduodenal infusion of Lipomul (2 ml/min), suggesting that the dose of GIP used was within the physiologic range. Intravenous infusion of three different doses of PYY (100, 200, or 400 pmol/kg.h) caused a significant inhibition of insulin release stimulated by GIP + glucose; the integrated insulin response was reduced to 105, 88, and 79 ng-60 min/ml, respectively. On the other hand, PYY (400 pmol/kg.h) had no effect on insulin secretion induced by intravenous glucose (0.6 g/kg.h) alone. These results indicate that PYY specifically inhibits the insulinotropic action of GIP and that PYY may play a negative-feedback regulatory role in the enteroinsular axis.

Inhibition of glucose-stimulated insulin release in the perfused rat pancreas by parathyroid secretory protein-I (chromogranin-A)

The effect of graded doses (10(-10)-10(8) M) of highly purified bovine parathyroid secretory protein-I (SP-I; chromogranin-A) or synthetic porcine pancreastatin on glucose-stimulated insulin release in the perfused rat pancreas was examined. SP-I (10(-9) M) inhibited the first phase of glucose-stimulated insulin release, and 10(-8) M SP-I inhibited both the first and second phases of glucose-stimulated insulin release; 10(-10) M SP-I was inactive. In comparison, pancreastatin at 10(-10) M inhibited the first phase of insulin release, and at 10(-9) and 10(-8) M, pancreastatin inhibited both phases of insulin release. The inhibition by SP-I was achieved at concentrations that normally exist in the general circulation of man. These and other data suggest that circulating SP-I plays a physiological role in the regulation of insulin secretion.

Evidence for regulation of peptide-YY release by the proximal gut

Peptide-YY (PYY) is a novel enteric peptide that is structurally related to pancreatic polypeptide and neuropeptide-Y. The objectives of the present experiments were to characterize the following aspects of PYY metabolism: the distribution of PYY in the canine gastrointestinal tract, the release of PYY in response to oral ingestion of a mixed meal or intraduodenal (ID) administration of oleic acid, the effect of ileocolectomy on the release of PYY in response to ID administration of oleic acid when transit of chyme to the distal ileum and colon is prevented, the effect of interruption of intramural neural pathways of the small bowel on the release of PYY, and the effect of iv cholecystokinin on the release of PYY. The results of these experiments demonstrate that PYY immunoreactivity is distributed primarily in the terminal ileum, colon, and rectum. Circulating levels of PYY increase significantly (P less than 0.05) within 10-30 min after ingestion of a meal or to ID administration of a fatty acid. Complete interruption of the flow of chyme to the site of PYY-containing cells (i.e. ileum-colon) did not block the release of PYY; however, ileocolectomy abolished the release of PYY in response to ID administration of oleic acid. Severance of intramural neural pathways along the small bowel did not alter the release of PYY in response to an oral meal. Intravenous administration of graded doses of cholecystokinin stimulated the release of PYY in a dose-related manner. The results of these experiments indicate that the release of PYY from the distal ileum and colon is controlled, at least in part, by an extramural neural, endocrine, or a combination of both types of mechanisms which originate in the foregut.

Intracerebroventricular administration of calcitonin enhances glucose-stimulated release of insulin

Intracerebroventricular (i.c.v.) administration of salmon calcitonin (500 ng) augmented glucose-stimulated release of insulin in rats. Vagotomy increased this enhancement effect of i.c.v. calcitonin significantly, whereas peripheral atropine treatment did not change it. Adrenal catecholamines did not participate in the centrally mediated insulinotropic effect of calcitonin since acute adrenalectomy did not modify the enhancement effect of i.c.v. calcitonin. Destruction of the sympathetic ganglia by neonatal treatment with 6-hydroxydopamine abolished the enhancement effect of i.c.v. calcitonin, which suggests that the sympathetic nervous system participates in the central action of calcitonin to enhance glucose-stimulated release of insulin.

Pancreatic juice enhances fat-stimulated release of enteric hormones in dogs

The presence of pancreatic juice in the intestinal lumen results in the hydrolysis of dietary fat. The hydrolytic products of dietary fat are potent stimulants of pancreatic exocrine secretion and potent inhibitors of gastric acid secretion. In this study, residual pancreatic enzyme activity in the intestinal lumen may account for the observed increase of triglyceride-stimulated pancreatic exocrine secretion and the release of peptides during diversion of pancreatic juice. The presence of pancreatic juice enhanced the pancreatic protein output that was stimulated by the intraduodenal administration of a triglyceride (corn oil, 2 g/kg/h) by 240% (p less than .05). The presence of pancreatic juice during the intraduodenal administration of a triglyceride nearly abolished the output of gastric acid as well as the release of gastrin (p less than .05) that had been stimulated by the intragastric placement of a 10% peptone meal. Pancreatic juice in the duodenum significantly enhanced the triglyceride-stimulated release of cholecystokinin-33/39, secretin, neurotensin, peptide YY, pancreatic polypeptide, and insulin (p less than .05) when compared with the release of these enteropancreatic hormones during the diversion of pancreatic juice. This study shows that the presence of pancreatic juice in the duodenal lumen enhances the fat-stimulated release of enteric hormones that have a stimulatory action on the enteroacinar and enteroinsular axis as well as an inhibitory action (enterogastrone-like activity) on the postprandial regulation of gastric function.

The effects of 2-deoxy-D-glucose and alpha-difluoromethylornithine on the growth of pancreatic cancer in vivo

The glycolytic inhibitor, 2-deoxy-D-glucose (2-DG), inhibits growth of some cancers. alpha-Difluoromethylornithine (DFMO) is an irreversible inhibitor of ornithine decarboxylase, the rate-limiting enzyme in polyamine biosynthesis. We and others have previously shown that DFMO inhibits cancer growth in a number of models. The present study was designed to investigate the effects of 2-DG alone and combined with DFMO on the growth of H2T hamster pancreatic ductal adenocarcinoma. Twenty-eight male Syrian golden hamsters were inoculated with 500,000 H2T cells, and then randomized into four groups of seven each: group 1 served as control; group 2 received DFMO (3% in drinking water); group 3 received 2-DG (500 mg/kg/day) intraperitoneally; group 4 received a combination of 2-DG and DFMO. Treatment began 5 days after tumor cell inoculation and continued for 28 days. At the end of the treatment period, the area of the H2T tumor was reduced 31% by DFMO compared with a 22% reduction caused by 2-DG. Tumor weight was significantly reduced (31%) by DFMO but not by 2-DG. Tumor contents of DNA, RNA, and protein were also reduced by DFMO but not 2-DG. Tumor concentration of the polyamines, putrescine and spermidine, were reduced by DFMO, but 2-DG did not alter levels of polyamines. The combination of DFMO and 2-DG caused a significantly greater reduction in tumor weight and putrescine content compared with DFMO alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of gamma-aminobutyric acid on bombesin-evoked release of somatostatin and gastrin from isolated rat stomach

The effect of gamma-aminobutyric acid (GABA) on basal and bombesin (BBS)-stimulated release of somatostatin (SLI) and gastrin from isolated perfused rat stomach was examined. In the control study, BBS at a dose of 10 nM significantly stimulated release of SLI and gastrin. Infusion of GABA (1-1000 nM) caused a depression of SLI release induced by BBS (10 nM) in a dose-dependent fashion. However, at doses used in this study GABA had no effect on either basal level of SLI and gastrin or BBS-elicited gastrin release. These results indicate that GABA can specifically modulate BBS-induced SLI release from rat stomach.

Clinical significance of gastrin receptors in human colon cancers

We have measured gastrin receptors (GR) in surgical specimens from 67 patients with primary colon cancers in order to determine the clinical significance of GR in colon cancer. GR analysis was performed on these specimens, and 22 cancers (32.8%) had no detectable GR. Thirty-eight cancers (56.7%) had high-affinity (Kd less than 1.0 nM) levels of GR. Seven cancers (10.4%) had only low-affinity GR (Kd greater than 1.0 nM). Twenty patients (29.9%) had cancers with GR greater than 10 fmol/mg protein. Mean GR content was significantly greater (11.8 +/- 2.9 fmol/mg protein) in Dukes' Stage A and B cancers when compared to Stage C and D cancers (6.2 +/- 1.6 fmol/mg protein). A significantly greater percentage (52.4%) of patients in the early stages (A and B) had tumors with greater than 10 fmol/mg protein compared to patients with more advanced (C and D) cancers (19.6%). GR content did not correlate with histological differentiation, patient age, or preoperative carcinoembryonic antigen levels. No difference in the GR content was noted between left and right colon cancers or in patients of different sex or race. GR content of normal colon mucosa correlated with the GR content of colon cancers from the same surgical specimen, suggesting that these tumors maintain their normal complement of GR. In the early period of follow-up, 12 of 43 (28%) Stage C and D patients with GR less than 10 fmol/mg protein have died, whereas all 8 Stage C and D patients with GR greater than 10 fmol/mg protein are alive. GR content of colon cancers may have prognostic significance and may identify a group of patients with colon cancer that may benefit from hormonal therapy with antigastrin drugs.

Uptake of 131I-metaiodobenzylguanidine by 6-23 rat medullary thyroid carcinoma

Uptake of 131iodine-metaiodobenzylguanidine (131I-MIBG) by 6-23 rat medullary thyroid carcinoma (MTC), was studied in vitro and in vivo. In vitro, there was an 8-fold increase in 131I uptake by 6-23 cells when labeled with 131I-MIBG (131I 24 +/- 15 cpm/10(6) cells, 131I-MIBG 196 +/- 9 cpm/10(6) cells). MIBG uptake in vitro was the same at 4 degrees C and 37 degrees C. In contrast, 131I-MIBG uptake by PC-12 rat pheochromocytoma cells were 200 times greater (131I-MIBG 42,412 +/- 6,755 cpm/10(6) cells). 131I-MIBG uptake by rat MTC cells in vitro were of a comparable magnitude to the uptake of 131I-MIBG by rat ileal enterochromaffin cells (RIE-1) and mouse colon cancer cells (MC-26). In vivo, uptake of 131I-MIBG by 6-23 MTC tumor was considerably less than in the normal tissues (muscle, liver, spleen, kidney, adrenal and thyroid). Gamma camera studies of 131I-MIBG uptake by 6-23 MTC tumors growing in Wag-Rij rats were only transiently positive in 1 out of 4 rats studied. We conclude that 131I-MIBG is poorly taken up by rat medullary thyroid carcinoma and is an unpredictable marker for localization of rat MTC.

Photoperiod influences the growth of colon cancer in mice

We have developed a mouse colon adenocarcinoma cell line that produces tumors in a dose-dependent manner when injected subcutaneously. Our previous work has demonstrated its sequential pattern of tumor area and weight under 12L:12D (12 hours light, 12 hours darkness) photoperiod. This study investigated whether shorter (6L:18D) or longer (18L:6D) photoperiods alter tumor growth. Significantly greater tumor area, weight, and group mortality were found in mice exposed to 12L:12D photoperiods as compared to either 6L:18D or 18L:6D photoperiods, and difluoromethylornithine (DFMO) was a more effective inhibitor of tumor growth under the 6L:18D photoperiod compared to 12L:12D. These results demonstrate an important role of photoperiod on tumor growth.

Species-specific effects of neurotensin on gallbladder contraction in vitro

We have previously shown that an in vivo administration of neurotensin (NT) stimulates contraction of dog gallbladder (GB), but produces dilatation of GB in humans. The objective of this study was to examine the effect of NT on human, dog, guinea pig, and rabbit GB in vitro, in order to delineate direct versus indirect actions of NT in different species and to evaluate the structure-activity relationships of NT. The effect of NT on the canine sphincter of Oddi (SOD) was also examined in vitro. Isolated longitudinal strips of GB from the four species given above and SOD from dogs were suspended in oxygenated Krebs buffer, and the isometric tension responses to various doses of NT, NT 8-13, NT 1-11, and xenopsin (XP) were determined. All the NT homologs, except NT 1-11, stimulated contraction of the dog GB and SOD in a dose-dependent manner. NT also caused dose-related stimulation of GB contraction from guinea pigs but did not stimulate or depress the contractile activity of human and rabbit GB strips. These results suggest that NT action on GB contraction is species-specific. Tetrodotoxin did not modify the contraction of dog GB and SOD in response to NT, indicating that NT mediates its contractile effects directly. The relaxing effect of NT on GB of humans in vivo, as previously reported by us, thus appears to be an indirect action.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined endoscopic and fluoroscopic balloon dilatation of a complex proximal jejunal stricture

Dilatation of esophageal strictures has been practiced for many years. More recently, balloon dilatation, with endoscopic guidance, has been applied to the stomach and the colon. The small bowel has been less accessible to the endoscope, and, as far as we have been able to determine, balloon dilatation of jejunal strictures has not been reported. We present a patient who was referred to us after curative resection of two abdomino-pelvic malignancies, external beam irradiation to the abdomen and pelvis, and multiple later operations for bowel obstruction and dehiscence of intestinal anastomoses. The bowel obstruction and anastomotic dehiscence occurred during the present hospitalization and resulted finally in the development of a high-output proximal jejunal fistula. The area of stricture, as seen by means of barium contrast, had two separate components with an associated acute angulation. We report the combined use of endoscopic and fluoroscopic manipulation and balloon dilatation of this complex stricture.

DNA synthetic activity in tumor-bearing mice

The rate of DNA synthesis in normal tissues exhibits circadian rhythmicity. However, there have been conflicting reports of the effects of tumor burden on the circadian rhythm of DNA synthesis in non-cancer tissues. We have developed a mouse colon cancer (MC-26) that exhibits different growth under different photoperiods. The purpose of this study was to analyze DNA synthetic activity in tissues removed from tumor-bearing and tumor-free mice maintained under two different photoperiods. Two groups each of approximately 80 male Balb/c mice were acclimated to one of two light-dark cycles, 12L:12D or 6L:18D. Half of each group were injected with 5.0 x 10(4) MC-26 cells. Twenty-two days later, all mice were killed in subgroups at 4-6 hr intervals over one 24-hr period. Colons and tumors were removed for measurement of DNA synthesis. Results were analyzed by means of one-way analysis of variance (ANOVA) in order to determine whether DNA synthesis varied significantly within groups over the 24-hr period. The DNA synthetic activity, as measured by uptake of tritiated thymidine, exhibited significant temporal variation in the colons of control (tumor-free) mice under both the 12L:12D and 6L:18D photoperiods. The colons of tumor-bearing mice failed to exhibit a fluctuation under a 12L:12D photoperiod but did show a significant 24-hr rhythm under the 6L:18D photoperiod. The subcutaneously growing cancers did not exhibit a circadian variation in DNA synthetic activity under either photoperiod. Both photoperiod and the presence of cancer appear to affect the DNA synthetic activity observed in mice bearing the MC-26 colon cancer.

Down-regulation of pancreatic growth and gallbladder contractility by bile salts

Luminal sequestration of bile salts with cholestyramine and the oral administration of bile salts represent current forms of therapy for some diseases. We have recently reported that secretion of these salts exerts negative feedback control on the release of cholecystokinin (CCK). The purpose of this study was to examine the effects of long-term alterations of luminal concentrations of bile salts on CCK target organs, the pancreas and gallbladder. The bile salt pool in adult guinea pigs was either enriched by feeding 0.5 percent sodium taurocholate or depleted by feeding 2 percent cholestyramine. Pancreatic growth, gallbladder contractility, the concentration of cholecystokinin receptors in the gallbladder muscle, and meal-stimulated plasma levels of cholecystokinin were significantly stimulated by feeding the bile salt sequestrant cholestyramine to guinea pigs. Administration of the bile salt taurocholate produced the opposite effects. Inhibition of CCK release by bile salts and up-regulation of CCK receptors by CCK may be the mechanisms responsible for the actions of bile salts on CCK target organs.

Calmodulin antagonist trifluoperazine inhibits polyamine biosynthesis and liver regeneration

Polyamines are essential for cell growth and differentiation. Trifluoperazine (TFP) is a potent, competitive inhibitor of the calcium-calmodulin complex. TFP, when given to rats after partial hepatectomy, causes a significant decrease in DNA synthesis. The purpose of this study was to examine the effects of TFP on polyamine biosynthesis and on liver regeneration after partial hepatectomy. TFP (60 mg/kg, bodyweight) or saline control was administered to 80 male Sprague-Dawley rats 2 h before, 2 h after, or at the time of hepatectomy. Polyamines (putrescine, spermidine and spermine) were measured at the time of hepatectomy, and at 6, 24, 48, and 72 h after hepatectomy. TFP, when it was administered either 2 h before or at time of hepatectomy, blocked increases in putrescine that are seen normally at 6 h after hepatectomy. When TFP was given at the time of partial hepatectomy, putrescine was increased at 24 h, and then returned to normal levels at 72 h. Spermidine was inhibited at 24 h, but not at 48 and 72 h. Spermine was not significantly altered at any time. The administration of TFP 2 h after hepatectomy did not significantly alter concentrations of polyamines. The weight of regenerating liver was decreased by TFP at 48 h (23 per cent) and 72 h (22 per cent) after hepatectomy. These findings provide evidence that the calcium-calmodulin complex is required for the synthesis of liver polyamines before liver regeneration can proceed.

Effect of aging on gastric acid secretion, serum gastrin, and antral gastrin content in rats

The purpose of this study was to characterize the effects of aging on gastric acid secretion and on serum and antral concentrations of gastrin in rats. Young and old Fischer 344 rats were prepared with gastric fistulas. Twenty-four hours after surgery, graded doses of human synthetic gastrin-17 (SHG-17) (2, 5, 10, 20, and 40 micrograms/kg) were given intravenously in random order. Gastric secretions were collected for gastric acid measurement before and at 15-min intervals after each dose of gastrin. In a separate study, blood was collected and the stomachs were removed for antral gastrin extraction from fed young and old rats. Serum and antral gastrin was measured by radioimmunoassay. The basal and gastrin-stimulated acid secretions were significantly decreased in aged rats compared to the young rats. The basal acid output was 0.4 +/- 0.2 microeq/15 min in the aged rats and 1.5 +/- 0.5 microeq/15 min in the young. The maximal acid output stimulated by gastrin was 11.1 +/- 1.8 microeq/15 min in the aged rats and 24.2 +/- 2.8 microeq/15 min in the young. Both serum and antral concentrations of gastrin were significantly decreased in aged rats. Serum gastrin concentration was 114.8 +/- 7.4 pg/ml in the aged rats and 192.0 +/- 14.4 pg/ml in the young. Antral gastrin concentration was 3.9 +/- 0.5 micrograms/g tissue in the aged rats, which was significantly less than the concentration in the young (6.5 +/- 0.4 micrograms/g tissue). Antral gastrin content did not change with aging.(ABSTRACT TRUNCATED AT 250 WORDS)