Biomedical subjects

C D Logsdon

Publications and source records attributed to C D Logsdon.

At least 55 records · Page 3Linked to original sources

PubMed1992

Transforming growth factor-beta (TGF-beta 1) inhibits pancreatic acinar cell growth.

Effects of transforming growth factor (TGF)-beta 1 on mouse pancreatic acinar cell growth and rapid intracellular responses to cholecystokinin (CCK) were examined in vitro. TGF-beta 1 inhibited [3H]thymidine incorporation stimulated by either the CCK analogue caerulein, epidermal growth factor, or insulin. TGF-beta 1 inhibition of growth stimulated by a maximal dose of caerulein (1 nM) was dose dependent with one-half maximal effects occurring at approximately 5 pM and maximal inhibition seen with 30 pM. In contrast to its effects on CCK-stimulated [3H]thymidine incorporation, TGF-beta 1 had no effect on CCK-stimulated increases in amylase release or intracellular Ca2+ concentration. To determine whether TGF-beta 1 might be an autocrine growth regulator, pancreatic mRNA was probed for the presence of TGF-beta 1 transcripts. TGF-beta 1 mRNA was not detected in whole pancreas but was detectable with increasing abundance over time in primary cultures of pancreatic acinar cells. The appearance of the TGF-beta 1 mRNA corresponded to the period of rapid cellular proliferation in vitro. These results suggest that TGF-beta 1 may be an autocrine growth inhibitor in the pancreas and that the inhibitory effects of TGF-beta 1 on pancreatic acinar cell growth occur at sites distal to those involved in stimulus-secretion coupling.

Animals↗

PubMed1992

CCK, bombesin, and carbachol stimulate c-fos, c-jun, and c-myc oncogene expression in rat pancreatic acini.

To identify possible nuclear signals mediating long-term regulation of the pancreas by gastrointestinal hormones, the expression of c-fos, c-jun, and c-myc was investigated in rat pancreatic acini. Stimulation of the acini with cholecystokinin octapeptide (CCK-8, 100 pM), bombesin (10 nM), or carbachol (10 microM), but not gastrin (100 nM), secretin (100 nM), or vasoactive intestinal peptide (10 nM) induced an increase in oncogene mRNA expression. The percent increases of c-fos, c-jun, and c-myc mRNA were 207 +/- 40, 171 +/- 26, and 46 +/- 19 (n = 5) for CCK-8; 223 +/- 71, 159 +/- 31, and 43 +/- 21 (n = 5) for bombesin; and 125 +/- 51, 123 +/- 58, and 67 +/- 19 (n = 5) for carbachol, respectively. CCK-induced increases in oncogene mRNA were rapid and transient. c-fos and c-jun mRNA levels were increased after 30 min stimulation, peaked at 1 h, and returned to basal level in 2 h. Activation of c-myc was more prolonged with levels remaining elevated for at least 3 h. The effects of CCK-8 were concentration dependent. Detectable stimulation was seen at 10 pM; maximal stimulation occurred at 10 nM and was not affected by further increase in the concentration of CCK-8. JMV-180, a high-affinity site CCK receptor agonist and low-affinity site antagonist, alone did not stimulate c-fos mRNA expression but inhibited c-fos mRNA expression induced by CCK-8. These results suggest that the interaction between CCK and the low-affinity state of the CCK receptor is responsible for oncogene activation.

Animals↗

PubMed1992

Effects of bombesin on pancreatic digestive enzyme gene expression.

We examined the effects of bombesin on rat pancreatic digestive enzyme gene expression using cloned complementary DNA probes for amylase, trypsinogen I, chymotrypsinogen B, and lysophospholipase. Rats were injected sc three times daily with 5 nmol/kg body wt bombesin. Pancreata were investigated after 6, 12, 24, 48, and 120 h of hormone treatment. Bombesin administration resulted in a time-dependent increase of pancreatic weight, as well as DNA and protein concentration. Cellular hypertrophy became evident after 48 h, and pancreatic hyperplasia occurred after 5 days of hormone treatment. Bombesin administration resulted in a time-dependent parallel decrease of amylase and lysophospholipase messenger RNA (mRNA) concentrations with maximal inhibition occurring after 120 h of bombesin treatment (13 +/- 1% and 14 +/- 3% of control, respectively, P less than 0.05, n = 6). In contrast, chymotrypsin and trypsin mRNA levels remained unaltered after bombesin treatment for up to 5 days. Amylase and chymotrypsin enzyme levels did not correlate with their respective mRNA concentrations. Both decreased to approximately 50% of control after 12 h and increased to 126 +/- 38% of control and 388 +/- 109% of control (P less than 0.05, n = 6), respectively, after 5 days of bombesin treatment. To test whether the bombesin regulation was mediated by the release of cholecystokinin (CCK), the specific CCK receptor antagonist L-364,718 (1 mg/kg body wt) was injected ip either alone, or 15 min before each bombesin injection for 5 days. Although the antagonist alone significantly reduced the mRNA concentrations for trypsin, chymotrypsin, and lysophospholipase to approximately 50%, it did not block the effects of bombesin on pancreatic digestive enzyme levels. These data therefore indicate that bombesin regulates pancreatic digestive enzyme mRNA and protein concentrations in a nonparallel manner; furthermore, CCK is not involved in mediating the bombesin effects on pancreatic gene expression.

Amylases↗

PubMed1991

Glucocorticoids stimulate ornithine decarboxylase gene expression in pancreatic AR42J cells.

The effects of dexamethasone on ornithine decarboxylase gene expression were examined in rat pancreatic AR42J cells. Dexamethasone increased ornithine decarboxylase activity and messenger RNA (mRNA) concentrations in a time-dependent manner, with a maximal effect at 12 hours (207% +/- 63% and 327% +/- 34% of control, respectively; n = 5). Ornithine decarboxylase mRNA levels returned to control values at 48 hours, whereas ornithine decarboxylase activity was decreased to 41% +/- 8% of control (n = 3). Dexamethasone induction of ornithine decarboxylase mRNA was dose dependent, with half-maximal effects at 10(-8) mol/L (210% +/- 20% of control; n = 4) and maximal effects at 10(-7) mol/L (327% +/- 26% of control; n = 4). The glucocorticoid antagonist RU 38486 blocked the dexamethasone effects in a dose-dependent manner, with maximal effects occurring at 10(-7) mol/L (120% +/- 18% of control; n = 3). When protein synthesis was blocked by addition of cycloheximide, ornithine decarboxylase mRNA levels remained unchanged in response to glucocorticoids, indicating a primary effect of dexamethasone. Furthermore, cycloheximide by itself had no significant effect on ornithine decarboxylase mRNA levels. Inhibition of transcription with actinomycin D showed a half-life for ornithine decarboxylase mRNA of approximately 240 minutes. Ornithine decarboxylase mRNA stability was not affected by dexamethasone pretreatment for 12 hours. Therefore, these data suggest that dexamethasone regulates ODC gene expression via glucocorticoid receptor-mediated gene transcription. Furthermore, translational mechanisms seem to be involved in glucocorticoid-regulated ornithine decarboxylase induction.

Animals↗

PubMed1991

Growth and differentiation of pancreatic acinar cells: independent effects of glucocorticoids on AR42J cells.

Dexamethasone (DEX) inhibits growth and induces differentiation in rat pancreatic acinar AR42J cells. We wished to determine whether growth and differentiation are mutually exclusive in AR42J cells and whether DEX effects on growth and differentiation are mutually dependent or independent. Inhibition of DNA synthesis, assessed by [3H]thymidine incorporation, was detectable after 6 h, half-maximal after 12 h, and complete after 18-h DEX treatment, at which time incorporation was reduced to 9.0% of control. The half-maximal effective dose for inhibition of DNA synthesis was 0.5 nM, and maximal inhibition was achieved with 10 nM DEX. This dose-response was similar to that previously reported for DEX-induced parameters of differentiation. The rank order of potency for inhibition of DNA synthesis by various steroid hormones was DEX greater than corticosterone greater than aldosterone greater than progesterone. Hydroxyurea or serum starvation inhibited growth to the same extent as DEX but did not induce differentiation. Moreover, hydroxyurea or serum starvation did not block the ability of DEX to induce differentiation. Addition of either EGF or insulin significantly reversed the growth inhibitory effects of submaximal (1 nM) DEX. In cultures released from growth inhibition, 1 nM DEX increased cellular amylase content 5.9- to 6.5-fold, similar to the amylase increase in growth-inhibited cultures. Therefore, growth inhibition and differentiation are independent delayed events regulated by DEX in AR42J cells.

Adrenal Cortex Hormones↗

PubMed1991

Glandular kallikrein gene expression is selectively down-regulated by glucocorticoids in pancreatic AR42J cells.

In this study we investigated the effects of steroid hormones on glandular kallikrein gene expression in the rat pancreatic acinar cell line AR42J. Using a cloned complementary DNA probe and a polyclonal antibody we demonstrated expression of a true glandular kallikrein gene and protein in AR42J cells by Western and Northern blot analysis. Dexamethasone resulted in a time-dependent parallel decrease of kallikrein messenger RNA and protein with a maximum at 12 and 72 h (30 +/- 10 and 8 +/- 0.5% of control, respectively, P less than 0.05, n = 6). In contrast, dexamethasone stimulated gene expression of two other serine proteases, chymotrypsin and trypsin, approximately 3 to 4-fold. The decrease of kallikrein concentration was dose dependent with half-maximal effects at 5 x 10(-8) M and maximal effects at 10(-7) M dexamethasone (23 +/- 6% of control, n = 3). The glucocorticoid antagonist RU 38486 blocked the glucocorticoid-induced decrease in cellular kallikrein content in a dose-dependent manner. Complete inhibition was observed at equimolar doses of dexamethasone and the antagonist. The inhibitory effect of dexamethasone was completely reversible after hormone withdrawal for 24 h. Neither estrogen, progesterone, testosterone, or aldosterone had significant effects on kallikrein expression. These data suggest that down-regulation of pancreatic kallikrein gene expression occurs selectively in response to glucocorticoids at a pretranslational level, mediated most likely by the glucocorticoid receptor.

Animals↗

PubMed1990

Expression of Ca2+ mobilizing receptors in Xenopus oocytes: a tool for receptor characterization.

In order to investigate the molecular characteristics of gastrointestinal hormone receptors, we have expressed their mRNAs in Xenopus laevis oocytes. Xenopus oocytes possess intrinsic muscarinic cholinergic receptors which couple to intracellular Ca2+ release. Release of intracellular Ca2+ was detected by an increase in 45Ca2+ release from preloaded oocytes or by using the Ca2+-sensitive fluorescent dye fura-2. Similarly, cholecystokinin (CCK) receptors expressed on the surface of oocytes which were injected with mRNA prepared from rat pancreatic acinar AR42J cells were readily detected by their ability to mobilize intracellular Ca2+. The CCK receptors expressed in oocytes showed similar binding characteristics as the native receptors. CCK receptor expression in the oocytes could be specifically blocked by hybridizing the mRNA with antisense oligonucleotides based on the highly conserved second transmembrane region of the HM4 muscarinic cholinergic receptor before injection. These latter results strongly suggest that the CCK receptor is a member of the G protein-linked receptor family. Thus, expression in Xenopus laevis oocytes provides a powerful tool for elucidation of the molecular characteristics of gastrointestinal hormone receptors.

Animals↗

PubMed1990

Effects of CCK on gene expression of endocrine pancreatic hormones.

Regulation of endocrine pancreatic hormone gene expression by cholecystokinin (CCK) was examined in the rat using cloned cDNA probes to quantify changes in specific mRNAs (insulin, glucagon, pancreatic polypeptide and somatostatin). Plasma CCK levels were raised to concentrations comparable to physiologic postprandial values either by including soybean trypsin inhibitor (SBTI) in the intraduodenal perfusate of an elemental diet (6.9 +/- 1.0 pM, n = 6), or by intravenous infusion of CCK-8 (6.0 +/- 0.9 pM, n = 6). SBTI infusion for 48 h resulted in a three- to fourfold increase in procarboxypeptidase B and kallikrein mRNA levels. Similar increases were observed when CCK was infused intravenously for 24 h. In contrast, neither SBTI intraduodenally, nor intravenous CCK had any effects on mRNA levels of insulin, glucagon, PP or somatostatin. These data therefore indicate that CCK at physiologic postprandial plasma concentrations stimulates pancreatic protease gene expression but has no effects on gene expression of endocrine pancreatic hormones.

Animals↗

PubMed1990

Pancreatic acinar cells in culture: expression of acinar and ductal antigens in a growth-related manner.

In the current study two monoclonal antibodies (mAb) were used to investigate the expression of adult acinar and duct cell-specific antigens and their relationship with cell growth in primary acinar cell cultures. We have previously found that adult mouse pancreatic acinar cells divide in primary culture. Furthermore, during growth the cells lose their differentiated morphology and exhibit decreased expression of secretory proteins, followed by some degree of morphological redifferentiation after reaching confluency. A mAb specific in the adult pancreas for acinar cells (mAb Acinar-1) and another specific in the adult pancreas for duct cells (mAb Duct-1) were generated using such cultures as the immunogen. The starting material for the cultures consisted of predominantly Acinar-1 positive cells which incorporated [3H]thymidine, as determined by autoradiography and immunofluorescence labeling. However, expression of the acinar antigen persisted for only the first 3 to 7 days in culture. By contrast, expression of the duct antigen was rare until after 5 days in culture and was highest at day 9, the peak of cell growth. Dual label immunofluorescence showed that during the growth phase fewer cells expressed the acinar antigen, most expressed the duct antigen, and occasional cells expressed both antigens. After reaching confluency, the growth rate declined from days 15 to 21, and the cells progressively regained the acinar antigen with a concomitant loss of the duct antigen. mAb labeling was morphometrically quantitated and showed that more than 97% of the labeled area was Acinar-1 positive at 3 days, which decreased to approximately 16% at day 9, and then returned to over 97% by day 21 of culture. Ultrastructural immunolabeling showed that Acinar-1 positive cells at 21 days had well organized rough endoplasmic reticulum and small apical vesicles, while Duct-1 positive cells were undifferentiated in appearance (day 9) or had numerous mitochondria (day 21). Thus, changes in cell-specific antigens were paralleled by cell type associated morphological characteristics and indicate that adult acinar cells can retrodifferentiate to a more duct-like cell while retaining the potential to express an acinar-specific antigen.

Animals↗

PubMed1989

Pancreatic kallikrein gene expression: effects of glucocorticoids in vivo and in vitro.

We examined the role of glucocorticoids in the regulation of pancreatic glandular kallikrein gene expression in vivo and in vitro. Adult male rats were adrenalectomized (Adx). Corticosterone pellets were administered to maintain either physiologic (Adx 1+) or high physiologic (Adx 3+) plasma corticosterone levels. Pancreatic kallikrein mRNA levels were examined by Northern hybridization and quantitated by slot-blot hybridization. Adrenalectomy resulted in a 75% +/- 14% (n = 4) increase in kallikrein mRNA as compared with sham-operated controls. This increase was completely reversed by exogenous corticosterone replacement to normal physiologic concentrations. Replacement with high corticosterone levels (Adx 3+) resulted in a decrease of kallikrein mRNA levels to 53% +/- 4% (n = 4) of controls. A significant negative correlation was observed between individual kallikrein mRNA levels and plasma corticosterone (r = -0.81, n = 12). In vitro, using the rat pancreatic acinar cell line AR42J, dexamethasone decreased kallikrein mRNA steady-state levels in a time- and dose-dependent manner. These data, therefore, indicate that physiologic concentrations of plasma corticosterone decrease pancreatic kallikrein mRNA levels in vivo, and that this is a direct effect on pancreatic acinar cells.

Adrenalectomy↗

PubMed1989

Pancreatic digestive enzyme gene expression: effects of CCK and soybean trypsin inhibitor.

Regulation of pancreatic gene expression by cholecystokinin (CCK) was examined in the rat using cloned cDNA probes to quantify changes in specific mRNAs (amylase, trypsinogen I, chymotrypsinogen B, and ribonuclease). Rats were administered intraduodenally an elemental liquid diet. Plasma CCK levels were raised to levels comparable to physiological postprandial levels either by intraduodenal perfusion with soybean trypsin inhibitor (SBTI) (6.9 +/- 1.0 pM, n = 8) or by continuous intravenous infusion with cholecystokinin octapeptide (CCK-8, 6.0 +/- 0.9 pM, n = 6). SBTI infusion resulted in fivefold increases in trypsinogen I and chymotrypsinogen B mRNA levels after 48 h. In contrast SBTI infusion had no effect on amylase mRNA levels and led to a decrease in ribonuclease mRNA levels to approximately 50% of control after 48 h. Intravenous infusion with CCK-8 for 24 h resulted in plasma levels of CCK comparable to those obtained with SBTI and had similar effects on digestive enzyme mRNA levels. These data suggested that SBTI acted via its ability to raise plasma CCK levels. To further test the specificity of these effects, animals were infused intraduodenally with the specific CCK receptor antagonist L364,718. Although the antagonist itself had no effect on digestive enzyme mRNA levels, antagonist treatment totally abolished the effects of both CCK infusion and SBTI treatment. These data therefore indicate that CCK regulates digestive enzyme gene expression at plasma concentrations comparable to physiological postprandial levels. Furthermore, the ability of SBTI infusion to increase plasma CCK accounts for its effects on pancreatic digestive enzyme mRNA levels.

Amylases↗

PubMed1989

Mechanisms of insulin-induced insulin-receptor downregulation. Decrease of receptor biosynthesis and mRNA levels.

The influence of insulin on the downregulation of its receptor was studied in AR42J cultured pancreatic acinar cells, a cell line that has been demonstrated to be metabolically responsive to insulin. Downregulation induced by insulin was time and dose dependent. After a 20-h incubation with 1 microM insulin, Scatchard analysis revealed approximately 80% loss of insulin receptors. Studies of receptor half-life indicated that treatment with insulin accelerated the degradation of both the alpha- and beta-subunits of the insulin receptor by 30-60%. In addition, biosynthetic-labeling studies indicated that insulin inhibited the biosynthesis of the insulin-receptor precursor by greater than 30%. This decreased biosynthesis of the precursor was associated with decreased production of mature receptor subunits. Poly(A)+ RNA was extracted from control cells and cells treated for 24 h with 100 nM insulin. Slot blots and Northern transfers revealed that insulin induced an approximately 50% decrease in insulin-receptor mRNA levels. Therefore, these studies indicate that insulin may diminish the concentration of its receptors in target cells by at least two mechanisms: acceleration of receptor degradation and inhibition of receptor biosynthesis at the level of mRNA.

Cell Line↗

PubMed1988

Mechanism of glucocorticoid receptor down-regulation by glucocorticoids.

The effect of glucocorticoids on the regulation of glucocorticoid receptor mRNA was studied in two different cell lines, human IM-9 lymphocytes and rat pancreatic acinar AR42J cells. Using a glucocorticoid receptor cDNA probe, glucocorticoid receptor mRNA was examined by Northern blot hybridization and quantitated by slot-blot hybridization. In IM-9 and AR42J cells, dexamethasone decreased steady-state glucocorticoid receptor mRNA levels to approximately 50% of control. This decrease occurred with a one-half time of 3 h for IM-9 cells and 6 h for AR42J cells. Dexamethasone was the most potent steroid tested with a one-half maximal effect occurring at 10 nM and a maximal effect occurring at 100 nM. Glucocorticoid receptor mRNA half-life and gene transcription were then studied to determine the mechanism of decreased mRNA levels. The glucocorticoid mRNA half-life was approximately 120 min in IM-9 cells and 240 min in AR42J cells; these rates were not affected by dexamethasone treatment. In contrast, the rate of glucocorticoid gene transcription as measured by run-on assays in IM-9 cells was decreased to 50 +/- 6% of control by dexamethasone. These results indicate therefore that glucocorticoids regulate glucocorticoid receptor mRNA levels by influencing gene transcription.

Animals↗

PubMed1988

Isolation and monolayer culture of guinea pig pancreatic duct epithelial cells.

Monolayers of cultured epithelial cells have been prepared from fragments of guinea pig pancreatic excretory ducts isolated by a simple procedure employing collagenase digestion and manual selection, through which virtually all of the ductal system can be recovered. The isolated fragments were cultured in enriched Waymouth's medium on extracellular matrices of various composition and thickness, including: thin (less than 5 micron) and thick (0.5 mm) layers of rat tail collagen; thin layers of human placental collagen; thin layers of Matrigel (a reconstituted basement membrane material); uncoated tissue culture plastic; and the cellulose ester membranes of Millipore Millicells. Cells spread rapidly from duct fragments cultured on uncoated plastic or on plastic coated with thin layers of rat tail collagen or human placental collagen and formed epithelial monolayers. However, these cells were squamous and lacked the abundant basolateral membrane amplification and apical microvilli characteristic of freshly isolated duct epithelial cells. Cells did not spread from duct fragments cultured on Matrigel. In contrast, when fragments of pancreatic ducts were explanted onto either a thick layer of rat tail collagen or onto Millicell membranes, cells readily spread and formed confluent monolayers of cuboidal epithelial cells characterized by abundant mitochondria, apical microvilli, and basolateral plasma membrane elaboration. These results demonstrate that different forms of extracellular matrix modulate the growth and differentiation of pancreatic duct epithelial cells, and that culture on a permeable substrate markedly enhances the maintenance of differentiated characteristics in this cell type. The monolayers formed on Millicell membranes should provide a useful model system for physiologic analysis of the regulation of electrolyte secretion by this epithelium.

Animals↗

PubMed1988

Expression of receptors for cholecystokinin and other Ca2+-mobilizing hormones in Xenopus oocytes.

The expression of receptors for cholecystokinin (CCK) and other similar acting Ca2+-mobilizing hormones was studied in Xenopus laevis oocytes. Poly(A)+ RNA was prepared from pancreatic AR42J cells, which normally express receptors for CCK and bombesin and the RNA injected into oocytes. The presence of these pancreatic receptors on the oocytes was then demonstrated by hormone-induced mobilization of 45Ca2+. CCK receptors were present 1 day (maximum, 2 days) after injection of RNA and were generally proportional to the amount of poly(A)+ RNA injected (1-50 ng). Oocyte CCK receptors retained selectivity for CCK analogs (CCK8 greater than unsulfated CCK8 greater than CCK4) and were blocked by the specific CCK receptor antagonist CR 1409. When poly(A)+ RNA was subjected to size fractionation on sucrose gradients, activity-inducing CCK receptors showed a single peak centered at 3 kilobases. The generality of this oocyte system for expressing Ca2+-mobilizing hormone receptors was further shown by expression of a response to bombesin after injection of AR42J cell RNA and a response to vasopressin and angiotensin II when poly(A)+ RNA from rat liver was injected. No response to CCK was demonstrable after injection of liver RNA, demonstrating the specificity of this assay.

Animals↗

PubMed1988

Synthesis and secretion of rat pancreatic proteins by Xenopus laevis oocytes.

An in vivo translation system, the Xenopus laevis oocyte, was employed to study the synthesis and secretion of pancreatic proteins. RNA was purified from normal and diabetic rat pancreas and normal rat liver by use of guanidine isothiocyanate lysis and cesium chloride gradient centrifugation. The presence of functional mRNA was documented by translation in a reticulocyte lysate that yielded precursors of all major secretory proteins, i.e., slightly higher Mr than proteins synthesized in situ by pancreatic acini. Mature X. laevis oocytes were then microinjected with either total RNA or purified mRNA. When oocytes were subsequently incubated with 35S-methionine, pancreatic secretory proteins or hepatic albumin could be immunoprecipitated from oocyte lysate with specific polyclonal antibodies against amylase, trypsin, ribonuclease, and albumin. Amylase was shown to be enzymatically active. Moreover, oocytes released pancreatic secretory proteins into the medium when injected with pancreatic RNA in a time-dependent manner. Only the mature form of amylase was secreted and secretion was not regulated by secretagogues. When a comparison was made after injection of RNA from diabetic pancreas known to contain altered amounts of individual mRNAs, there was a decrease in amylase and an increase in trypsinogen synthesis in oocytes that was comparable to the results of cell free translation. The oocyte expression system, therefore, should be useful not only for studies of protein synthesis but also for processing and secretion.

Albumins↗

PubMed1988

Effects of cholecystokinin on pancreatic ornithine decarboxylase gene expression.

The effects of cholecystokinin (CCK) on pancreatic ornithine decarboxylase (ODC) gene expression were studied in the rat. Plasma CCK concentrations were raised to levels comparable to postprandial values either by intravenous infusion of CCK octapeptide (CCK-8) or by intraduodenal perfusion of soybean trypsin inhibitor (SBTI). ODC mRNA levels were quantified using a cloned cDNA probe. ODC mRNA increased to 166 +/- 34% (n = 4) of control after 1 h, peaked at 254 +/- 39% (n = 4) of control after 24 h, and remained significantly elevated for up to 48 h of SBTI infusion. Intravenous infusion of CCK-8 for 24 h increased ODC mRNA levels to the same extent observed with SBTI infusion. The CCK receptor antagonist L364,718 by itself had no effect on ODC mRNA levels but totally abolished the induction of ODC mRNA by both intravenous CCK infusion and intraduodenal infusion of SBTI. These data therefore indicate that CCK plasma concentrations comparable to postprandial values regulate pancreatic ODC at a pretranslational level and that SBTI exerts its effects on pancreatic ODC via an increase in plasma CCK.

Animals↗

PubMed1988

Monoclonal antibodies as probes for plasma membrane domains in the exocrine pancreas.

Monoclonal antibodies (mAb) were generated as probes for the plasma membrane domains of pancreatic acinar cells. Primary monolayer cultures of mouse pancreatic acinar cells, which have an expanded apical surface relative to normal pancreas, were used to immunize rats. With conventional immunization and fusion protocols, 3% of the hybridomas were positive against the acinar lumen by indirect immunofluorescence of mouse pancreas cryosections. Culturing of spleen cells from an immunized rat on the apical surface of acinar cell monolayer cultures before fusion with the myeloma (an in vitro boost) doubled the percentage of hybridomas producing apical membrane-specific mAb. Monoclonal antibodies were characterized by immunofluorescence, ultrastructural immunoperoxidase cytochemistry, immunoprecipitation, and immunoblotting. One antibody, acinar-1 (IgG2a), labeled the apical membranes of pancreatic acinar cells, hepatocytes, salivary and lacrimal gland acinar cells, and the brush border of small intestine enterocytes. This mAb precipitated and blotted a protein of 94 KD. Acinar-2 (IgM) also labeled pancreatic acinar cell apical membranes but did not label other tissues and did not precipitate or blot. Acinar-3 labeled pancreatic acinar cell lateral membranes. Duct-1 (IgM) labeled pancreatic duct apical membrane and ducts in liver and salivary glands but did not precipitate or blot. These domain-specific mAb demonstrate that common antigenic determinants occur in the apical surfaces of several exocrine epithelia and may be important in secretion.

Animals↗