Differences in glucose handling by pancreatic A- and B-cells

Glucose exerts opposite effects upon glucagon and insulin release from the endocrine pancreas. Glucose uptake and oxidation were therefore compared in purified A- and B-cells. In purified B-cells, the intracellular concentration of glucose or 3-O-methyl-D-glucose equilibrates within 2 min with the extracellular levels, and, like in intact islets, the rate of glucose oxidation displays a sigmoidal dose-response curve for glucose. In contrast, even after 5 min of incubation, the apparent distribution space of D-glucose or 3-O-methyl-D-glucose in A-cells remains much lower than the intracellular volume. In A-cells, both the rate of 3-O-methyl-D-glucose uptake and glucose oxidation proceed proportional to the hexose concentration up to 10 mM and reach saturation at higher concentrations. Addition of insulin failed to affect 3-O-methyl-D-glucose or D-glucose uptake and glucose oxidation by purified A-cells. Glucose releases 30-fold more insulin from islets than from single B-cells, but this marked difference is not associated with differences in glucose handling. The rate of glucose oxidation is virtually identical in single and reaggregated B-cells and is not altered after addition of glucagon or somatostatin. It is concluded that the dependency of glucose-induced insulin release upon the functional coordination between islet cells is not mediated through changes in glucose metabolism.     

Histochemistry of the pancreatic islets in golden hamsterMesocricetus auratus waterhouse 1839

Summary The histological picuture of the Langerhans' islets in hamster pancreas is quite similar to that in white rat pancreas, i.e. the B-cells are located in the middle of the islet, while the A-cells in its periphery. Very often the argyrophil cells (D-cells) are located between the A- and B-cells forming a peculiar “barrier”. The histochemical studies reveal differences between the endocrine tissue and exocrine parenchyma. In general, the islet cells are richer in enzymes, as compared with the acini. The histochemical characteristic of hamster pancreas is closest to that of white rat pancreas. Like in rat, alkaline phosphomonoesterase reaction is very strong in the A-cells, while G-6-P reaction is negative. But, concerning zinc localization, there are differences between hamster and rat. Zinc reaction is very strong in the peripheral A-cells in white rat pancreas, while in hamster this reaction is much stronger in the B-cells (the reaction is negative in the A-cells). The D-cells can not be differentiated from the other endocrine pancreatic cells by means of hystochemical studies. But these studies permit certain conclusion on the possible role of the enzymes and substances investigated in cytophysiology of the islet cells.     

Rodent pancreatic islet cells contain the calcium-binding proteins calcineurin and calretinin

 Calcium is known to be of critical importance for hormone secretion in the insulin-producing B-cells of the endocrine pancreas. Calcium-mediated intracellular signal transduction and the regulation of the concentration of free calcium in B-cells probably involve calcium-binding proteins. In the present study, we have investigated the expression of the calcium/calmodulin-dependent phosphatase, calcineurin, and the EF-hand calcium-binding protein, calretinin, in pancreata of hamsters, gerbils, and rats by immunocytochemistry. Immunocytochemical investigations of serial semithin sections of plastic-embedded pancreata revealed that calcineurin and calretinin were constantly present in islet cells of all three species. In addition to B-cells, these proteins could also be detected in glucagon (A-), somatostatin (D-), and pancreatic polypeptide (PP-) cells. Non-B-cells, especially glucagon-producing A-cells, often exhibited a significantly higher degree of immunoreactivity for both calcium-binding proteins than B-cells. Thus, calcineurin and calretinin may play distinct roles in the regulation of calcium-dependent secretory activities of the different pancreatic endocrine cell types. Accepted: 10 April 1997     

Differential staining of pancreatic islet A- and B-cells using Rouge's fixative and a modified Gomori method]

Roug's fixative fluid is suggested to fix the pancreas with subsequent staining of the islet A- and B-cells. Rouget's fluid differs from Bouin's fluid in that picric acid is substituted for distilled water, and thus, it is unnecesary to extract the acid from the preparation. The fixation ensures good quality in demonstration specific granulation and preserves it in B-cells. Gormori's modification of the method to stain the slices with aldehyd-fuchsin and subsequent staining with alum carmine and orange G reveals both B- and A-cells. The manipulations presented perfect the quality of histochemical reactions.     

Occurrence of biogenic amines in the pancreatic islets of sand rats (Psammomys obesus).

The islets of Langerhans of sand rats (Psammomys obesus) have been investigated ultrahistochemically in order to demonstrate biogenic amines. It could be found that amine-containing vesicles with a diameter of 600-700 nm from the type of catecholamine-granules exist in A-cells as well as in B-cells. It can be stated that the sand rat belongs to the species containing amines in A- and B-cells. The importance of the amines for the regulation of the hormone secretion of the islets of Langerhans is discussed and the connections to diabetes mellitus are referred too.     

Immunocytochemical localization of cathepsins B and H in human pancreatic endocrine cells and insulinoma cells

Cathepsins B and H are representative cysteine proteinases localized to lysosomes of a variety of mammalian cells. Previous studies indicated the presence of these enzymes also in secretory granules of endocrine cells. Therefore, the human endocrine pancreas and human insulinomas were investigated by light microscopical immunohistochemistry on serial semithin plastic sections immunostained sequentially for cathepsins B or H and pancreatic hormones. Out of the four established endocrine cell types, insulin (B-) and glucagon (A-) cells showed immunoreactivities for these cathepsins. Cathepsin B immunoreactivities showed a dot-like appearance in A- and B-cells and in insulinoma cells. Immunoreactivities for cathepsin H additionally were found in cell parts containing secretory granules of B-cells and insulinoma cells. By single and double immunoelectron microscopy the dot-like immunoreactivities for cathepsin B were identified as immunoreactive lysosomes of A- and B-cells and insulinoma cells. In addition, some of the secretory granules of A- and B-cells showed cathepsin B immunoreactivities. Cathepsin H immunoreactivities showed an other pattern: they were found regularly in the secretory granules of A- and B-cells and insulinoma cells, and in lysosomes of A-cells. These findings suggest that cathepsins B and H in lysosomes of A- and/or B-cells are involved in the degradation of lysosomal constituents. In secretory granules of these cells, these cysteine proteinases may participate in the processing of the corresponding hormones from their precursor proteins.     

Immunocytochemical localization of cathepsins B and H in human pancreatic endocrine cells and insulinoma cells

Summary Cathepsins B and H are representative cysteine proteinases localized to lysosomes of a variety of mammalian cells. Previous studies indicated the presence of these enzymes also in secretory granules of endocrine cells. Therefore, the human endocrine pancreas and human insulinomas were investigated by light microscopical immunohistochemistry on serial semithin plastic sections immunostained sequentially for cathepsins B or H and pancreatic hormones. Out of the four established endocrine cell types, insulin (B-) and glucagon (A-) cells showed immunoreactivities for these cathepsins. Cathepsin B immunoreactivities showed a dot-like appearance in A- and B-cells and in insulinoma cells. Immunoreactivities for cathepsin H additionally were found in cell parts containing secretory granules of B-cells and insulinoma cells. By single and double immunoelectron microscopy the dot-like immunoreactivities for cathepsin B were identified as immunoreactive lysosomes of A- and B-cells and insulinoma cells. In addition, some of the secretory granules of A- and B-cells showed cathepsin B immunoreactivities. Cathepsin H immunoreactivities showed an other pattern: they were found regularly in the secretory granules of A- and B-cells and insulinoma cells, and in lysosomes of A-cells. These findings suggest that cathepsins B and H in lysosomes of A- and/or B-cells are involved in the degradation of lysosomal constituents. In secretory granules of these cells, these cystine proteinases may participate in the processing of the corresponding hormones from their precursor proteins.     

Expression of novel organic cation/carnitine transporter (OCTN2) in the mouse pancreas

Among the organic cation transporters, OCTN2 is identified as the most important carnitine transporter owing to the ability to transport carnitine. Although the OCTN2 is previously found in various tissues, there have been no reports showing the OCTN2 in the pancreas. In this study, we examined the expression and localization of OCTN2 in the mouse pancreas by the aid of an in situ hybridization technique and immunohistochemistry with anti-OCTN2 antibody. As a result, the OCTN2 expression was found in the A-cells for the first time. OCTN2 was not expressed in B-cells, notwithstanding that the metabolism of long-chain fatty acids, which are transported into the mitochondria with the help of carnitine, was expected for fatty acid-stimulated insulin secretion. Thus, this study suggests the possibility of carnitine uptake in the pancreatic A-cells through OCTN2 and implies the presence of carnitine transporter(s) other than OCTN2 in the B-cell.     

Immunohistochemistry of opioid peptides in the guinea pig endocrine pancreas

Summary Previous immunochemical investigations have demonstrated various opioid peptides in the pancreas. However, controversies exist related to the cellular localization of these peptides in the endocrine pancreas. Therefore, the guinea pig endocrine pancreas was immunohistochemically investigated for the presence of opioid peptides derived from pro-dynorphin, pro-enkephalin or pro-opiomelanocortin. Immunoreactivities were demonstrated on serial semithin sections by the peroxidase anti-peroxidase technique. In routinely immunostained sections, immunoreactivities for dynorphin A and -neo-endorphin were localized in pancreatic enterochromaffin cells, but not in islet cells. Immunoreactivity for Met-enkephalin was confined exclusively to B-cells and was localized only in some secretory granules. However, pre-treatment of semi-thin sections with trypsin and carboxypeptidase B led to a marked increase of Met-enkephalin immunoreactivity in B-cells. In addition, immunoreactivities for Met-enkephalin-Arg-Gly-Leu and bovine adrenal medulla dodecapeptide could be demonstrated in B-and A-cells, and -endorphin immunoreactivity was localized in A-cells. In no case, however, were immunoreactivities detected for bovine adrenal medulla docosapeptide, peptide F, corticotropin, melanotropin or dynorphin 1–32. The immunohistochemical findings indicate that opioids of different peptide families are present in the guinea pig endocrine pancreas. Since several opioid peptides of the corresponding pro-hormones could be demonstrated in the reference organs but not in the pancreas, it is concluded that the biosynthetic pathways of the respective precursors are different from those in the adrenal medulla or in the pituitary.     

Waveform tuning of electroreceptor cells in the weakly electric fish, Gnathonemus petersii

Electroreceptive afferents from A- and B-electroreceptor cells of mormyromasts and Knollenorgans were tested for their sensitivity to different stimulus waveforms in the weakly electric fish Gnathonemus petersii. Both A- and B-mormyromast cells had their lowest sensitivity to a waveform similar to the self-generated electric organ discharge (EOD) (around 0° phase-shift). Highest sensitivities, i.e. lowest response thresholds, in both A- and B-cells were measured at phase shifts of +135°. Thus, both cell types were inversely waveform tuned. The sensitivity of B-cells increased sharply with increasing waveform distortions. Their tuning curves had a sharp minimum of sensitivity at +7° phase shift. A-cells had a much broader waveform tuning with a plateau level of low sensitivity from +24° to −15°. Across a 360° cycle of phase-shifts, the range of thresholds was 16 dB for individual B-cells and 4.5 dB for individual A-cells. Knollenorgan afferents were tuned to 0° phase-shifted EODs and had a dynamic range of 12 dB. Lowest sensitivities were measured at a phase shift of +165°. Experiments with computer-generated stimuli revealed that the strong sensitivity of mormyromast B-cells of EOD waveform distortions cannot be attributed to any of the seven waveform parameters tested. In addition, EOD stimuli must have the correct duration for B-cells to respond to waveform distortions. Thus, waveform tuning appears to be based on the specific combination of several waveform parameters that occur only with natural EODs. Accepted: 28 April 1997     

Quantitative immunocytochemical analysis of the endocrine pancreas of the Nile crocodile

Four major pancreatic hormones were immunolocalized at the light and electron microscopic levels in the pancreas of the Nile crocodile, Crocodilus niloticus. Immunogold was used for electron microscopy, and peroxidase-antiperoxidase was used for light microscopy. Somatostatin-positive D-cells and pancreatic polypeptide-containing F-cells accounted for about 60% of the immunoreactive cells in the ventral pancreas. Glucagon-positive A-cells were the least frequent cell type in the ventral pancreas, about 15%, but were the predominant cell type, about 40%, in the pancreas that was dorsal in character. An expanded population of D-cells (relative to mammals and other higher vertebrates) in association with two very different numbers of A-cells can be expected to have important consequences for the homotropic control of secretory activity of the endocrine pancreas as well as for the function of the acinar pancreas. F-cells were absent from the dorsal part of the pancreas, whereas insulin-containing B-cells were slightly more abundant in this portion of the pancreas. The regional character of the endocrine pancreas was related to the complex looping of the proximal small intestine. Without immunolabeling, only B-granules were morphognomonic in electron micrographs. The insulin-reactive B-granules were the smallest (370 nm) of the secretory granules and were followed in size by somatostatin-positive D-granules (380 nm). The pancreatic polypeptide-containing secretory granules were the largest (580 nm). Glucagon-reactive A-granules (430 nm) sometimes exhibited a protuberance or extension of secretory granule matrix and limiting membrane. Such a morphological feature has previously been associated with secretion of glucagon and the initiation of insulin secretion. Taken together these studies indicate that protuberances have a significant, but as yet undefined, role in pancreatic endocrine cells.     

Studies on the neurosecretory system of Ranatra elongata fabricius (Hemiptera: Nepidae) with reference to the distal fate of NCC I and II

With the help of PF and PAVB bulk-stained preparations and sections the neurosecretory system of Ranatra elongata has been described. Two medial, each of 9-10 cells, and two lateral, each of 3-4 cells, groups of neurosecretory cells have been observed in the protocerebrum. Only the A-cells have been found to be positive to PAVB histo- and cyto-chemical technique. Axons of the A-cells after traversing the proto- and deuto-cerebrum emerge from the tritocerebrum as the NCC I. The NCC I after bypassing the corpora cardiaca penetrate the aorta wall. There is no physical continuity between the corpora cardiaca and the NCC I and the two are separable. The NSM from the A-cells, transported by their nerve fibers, has been observed in the aorta wall. On the basis of large accumulation on NSM in the aorta wall the latter has been considered as the storage-and-release organ for the A-material. Corpora cardiaca are found to be devoid of A-material. Axons from the B-cells, after emergence from the tritocerebrum as the NCC II, have been observed to penetrate the corpora cardiaca. On the basis of ample amounts of B-material the glands have been considered as the storage-and-release organ for the B-material only. Observations are compared with results on related species and it is concluded that two independent organ complexes constitute the neurosecretory systemt of R. elongata. The A-cells, their pathways, the NCC I, and the aorta wall comprise the first; and the B-cells, their pathways, the NCC II, and the corpora cardiaca the second. The former is concerned with the elaboration, transportion, storage-and-release of the A-material and the latter with the B-material. Finally arguments are presented to include the aorta wall in the neurosecretory system.     

Neurosecretory cells in the central nervous system of the adult blowfly, Phormia regina Meigen (Diptera: Calliphoridae)

• 1 Neurosecretary cells in the central nervous system of the adult blowfly, Phormia regina Meig., have been examined histologically using the parparaldehyde-fuchsin and Gomori's staining method. Six groups of the neurosecretory cells occur in each hemisphere of the brain, the medial, frontal, lateral A, lateral B, posterior I and posterior II groups. In the subesophageal ganglion, four B-cells and two A-cells are present. In the thoracico-abdominal ganglion, ten A-cells are found in the thoracic region and a total of about 50 A- and B-cells in the hind part of the abdominal region.
• 2 A comparison with the neurosecretory system of two other species of blowfly, Calliphora erythrocephala Meig., Sarcophaga bullata Parker, and the housefly, Musca domestica L., showed similar arrangements and grouping.
• 3 Neurosecretory granules have been observed along the axons originating from the medial neurosecretory cells of the brain, and the thoracico-abdominal ganglion. The granules originating from the medial groups can be traced directly to the corpus cardiacum from which they move to the aorta, crop duct and cardia through axons.
• 4 There is with advancing age a gradual increase in the size of cell bodies and nuclei of the median neurosecretory cells in both females and males of Phormia regina, and also a decrease in stainable granules. This increase in size is dependent on nutrition, with no increase in water alone, a slight increase on sugar, and a maximum increase on sugar and liver. Corresponding increases in size occur in the ovaries in connection with feeding the same substances.

     

Pancreatic lesions of small-obese mice (C57BL/6 J-ob/ob) with hyperglucagonemia

Male Small-obese mice (Small-ob) which derived from a C57BL/6 J-ob/ob mouse colony were examined histopathologically at 13-, 39-, and over 52-week-old. C57BL/6 J-ob mice (?/+: Non-ob, ob/ob: Ob) were studied as controls. In Small-ob mice, plasma glucagon concentration was higher than that of the Ob mice (this difference was highly significant), and serum levels for insulin was within normal limits. Microscopically, hypertrophy and hyperplasia of the islets of Langerhans were found only in the pancreas of Ob mice. The increase in the number of A-cells and the decrease in the number of B-cells were revealed immunohistochemically in the islets of Small-ob mice. These changes were more severe with advance of age. In the aged Small-ob mice, perivascular and periductular cell infiltration were found, but inflammatory change of islet tissue was not confirmed in any animals examined. Diabetic symptoms in Small-ob mice seems to stem from the disparity in insulin/glucagon (I/G) ratio associated with hyperglucagonemia which result from increased number of A-cells of pancreatic islets.     

Cellular and subcellular expression of Golf/Gs and Gq/G11 alpha-subunits in rat pancreatic endocrine cells.

We studied the cellular and subcellular localization of Galpha-subunits in pancreas by immunocytochemistry. Golfalpha and G11alpha were specifically localized in islet insulin B-cells and glucagon A-cells, respectively. Gsalpha and Gqalpha labeling was more abundant in B-cells. The presence of Golfalpha in B-cells was confirmed by in situ hybridization. In B-cells, Golfalpha and Gsalpha were found in the Golgi apparatus, plasma membrane (PM) and, remarkably, in mature and immature insulin secretory granules, mainly at the periphery of the insulin grains. Gqalpha was detected on the rough endoplasmic reticulum (RER) near the Golgi apparatus. In A-cells, the Galpha-subunits were mostly within the glucagon granules: G11alpha gave the strongest signal, Gsalpha less strong, Gq was scarce, and Golf was practically absent. Gqalpha and Gsalpha immunoreactivity was detected in acinar cells, although it was much weaker than that in islet cells. The cell-dependent distribution of the Galpha-subunits indicates that the stimulatory pathways for pancreatic function differ in acinar and in islet B- and A-cells. Furthermore, the G-protein subunits in islet cell secretory granules might be functional and participate in granule trafficking and hormone secretion.     

Comparative morphology of the endocrine portion of the mammalian pancreas]

The endocrinous part of the pancreas in the mammals under investigation (rats, guinea pigs, cattle, cats and man) comprises A-, B- and D-cells always disposed around capillaries were prevailing in all the animals. They excrete the secretory product immediately into the pericapillary gap. A-cells in rodents and man are located in the periphery of the island and often have no contacts with capillaries. The secretion from A- cells having no contacts with capillaries is released into intercapillary clefts into which the cytoplasmic spiculae of the adjacent exocrinous pancreacytes are turned, capable to overlap them and prevent from the entering of the hormone from the intercellular clefts into the pericapillary gap.     

Increase in B-cells in the pancreatic remnant after partial pancreatectomy in pigs. An immunocytochemical and functional study

The regenerative and functional capacity of B-cells in the remaining pancreatic tissue after surgical removal of 40%, 60% and 80% of the pancreas was examined in 7 month old pigs (three animals in each group). Prior to resection and 1, 3 and 6 weeks after surgery, basal and glucose-stimulated levels of insulin and blood glucose were determined and compared with the preoperative data and that of sham-operated controls. For quantitative morphology, the volume of the resected specimen and the residual pancreatic tissue, 6 weeks after surgery, was determined and sections evaluated by immunocytochemistry (insulin, glucagon, somatostatin, pancreatic polypeptide) combined with morphometry. In the remaining pancreas, the volume density of the B-cells was increased by 19% (1.57-1.92 after 60% resection; p less than 0.02) and 56% (1.57-2.38 after 80% resection; p less than 0.02) 6 weeks after surgery, compared with the respective resected portion of the pancreas and the controls (n = 12). The non-B-cells gained between 0-10% (PP-cells), 10-20% (D-cells) and 30-40% (A-cells) in the different resection groups. As the number of B-cells per given islet area remained unchanged (mean 4.12 cells/0.25 mm2), the increased volume density was due to an increase in cell number rather than cell size. Insulin secretion (integrated values, 0-120 min), was not significantly impaired after 40% and 60% resection (2711 +/- 250 all preoperative samples; 3215 +/- 474 40% at 6 week intravenous glucose tolerance test (IV-GTT); 1677 +/- 109 60% at 6 week IV-GTT), although the glucose levels (integrated values) were increased during the IV-GTT. The 80% resected animals showed a significant decrease in the insulin response only 1 week after surgery (integrated values: 2711 +/- 250 all preoperative samples, compared with 1250 +/- 508 1 week IV-GTT; p less than 0.05), while the integrated glucose values during IV-GTT (0-120 min) were significantly elevated throughout the observation period. These results suggest a B-cell hyperplasia in the residual pancreas after resection, which may cope with a normal functional demand, but disclose functional abnormalities when challenged with an increased glucose load.     

Die postnatale Entwicklung der Harderschen Drüse der weißen Ratte

Summary The postnatal development of the Harderian gland of the rat was studied by light microscopy using paraffin- and epon-embedded tissues of animals ranging from newly born to the age of 13 weeks.In one week old rats two types of glandular cells can be distinguished: A-cells and B-cells. At this time the more numerous A-cells are less vacuolated than the B-cells. When the rats have opened their eyes (14th day) conspicuous changes in the morphology of the Harderian gland become evident: There is a pronounced increase in secretory activity, in cytoplasmic vacuolation (particularly of the A-cells) in cell height and in the diameters of the tubular endpieces. At the end of the 2nd week the occurrence of a third cell type (C-cells) with pale cytoplasm and pycnotic nucleus is observed. C-cells are interpreted to be necrobiotic A-cells or B-cells. It is considered that the Harderian gland might have not only an apocrine (or merocrine ?) but also a holocrine mode of secretion.At the 9th day the first yellowish-brown pigment granules can be observed in some of the glandular lumina. One day earlier some areas of the gland (unstained kryostat sections) exhibit a pink fluorescence in ultra-violet light, indicating the presence of porphyrin. The pigmentation of the gland reaches highest intensity about the 3rd and 4th postnatal weeks. Sex dimorphism with respect to pigmentation has not been stated. From the histogenesis there was also no support for a sex dependent function of the Harderian gland.Zusammenfassung Die Hardersche Drüse neugeborener bis 13 Wochen alter Ratten wurde an Hand von Paraffin- und Eponschnitten untersucht.Dabei ließen sich bereits im Alter von 1 Woche erste Zeichen einer intrazellulären Sekretbildung in Form feiner Fetttropfen beobachten und zwei Zelltypen (A- und B-Zellen) unterscheiden, von denen die B-Zellen zunächst dichter vakuolisiert sind als die zahlreicheren A-Zellen. Nach der Öffnung der Lidspalte am 14. Lebenstage steigt die Aktivität der Drüsenzellen deutlich an, wobei die Sekrettropfen — vor allem in den A-Zellen — an Zahl und Durchmesser zunehmen und die Zellen vergrößert werden. Gegen Ende der 2. Lebenswoche treten neben den genannten Zelltypen auffallend blaß getönte Zellen mit z. T. pyknotischen Kernen auf (C-Zellen), die als zugrundgehende A- oder B-Zellen gedeutet werden. Es wird in Erwägung gezogen, daß die Hardersche Drüse nicht nur nach dem apokrinen (oder merokrinen ?), sondern auch nach dem holokrinen Mechanismus sezerniert.Die bei erwachsenen Tieren mehrfach beschriebenen porphyrinhaltigen Pigmentkörnchen in den Drüsenlichtungen treten erstmals im Alter von 9 Tagen auf. Porphyrin läßt sich fluoreszenzmikroskopisch bereits 1 Tag vorher nachweisen. Die intensivste Pigmentierung der Drüse besteht während der 3. und 4. Lebenswoche. Eindeutige Geschlechtsunterschiede bezüglich der Pigmentierung waren nicht festzustellen. Auch aus der Histogenese ergab sich kein Anhalt für eine geschlechtsgebundene Funktion der Harderschen Drüse.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft (Pe-Epithel).     

Immunocytochemical finding of the amidating enzymes in mouse pancreatic A-, B-, and D-cells: a comparison with human and rat.

alpha-Amidation is catalyzed by two enzymatic activities, peptidyl-glycine alpha-hydroxylating mono-oxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL), denoted collectively as peptidyl-glycine alpha-amidating mono-oxygenase (PAM), which also may include transmembrane and cytoplasmic domains. PAM is present in mammalian pancreas, where it appears to be abundant in the perinatal period. Nevertheless, there is no agreement on the cell type(s) that produces PAM or even on its presence in adults. In the present study we found PAM (PHM and cytoplasmic domain) immunoreactivity (IR) in A-, B-, and D-cells of adult mouse pancreas. In contrast to previous reports, PAM IR was found in B-cells of human and rat. Most of the B/D-cells were PAM immunoreactive, although with variable intensity, whereas less than half of A-cells displayed IR. Immunocytochemistry and Western blotting suggested the existence of different PAM molecules. Differences in the cellular distribution of IR for PAM domains were also observed. Whereas PHM-IR was extended throughout the cytoplasm in the three cell types, presumably in the secretory granules, IR for the cytoplasmic domain in A/D-cells was restricted to a juxtanuclear region, perhaps indicating its cleavage in Golgi areas. Although glucagon, insulin, and somatostatin are non-amidated, amidated peptides (glucagon-like peptide 1, adrenomedullin, proadrenomedullin N-terminal 20 peptide) were found in the three cell types.     

Evidence for secretion of 7B2 by A- and B-cells of hamster pancreatic islets.

7B2 is a neuroendocrine protein, and in the pancreatic islets the presence of 7B2 in A- and B-cells was immunohistochemically demonstrated. In order to examine 7B2 secretion by A- and B-cells of pancreatic islets, we prepared isolated hamster pancreatic islet cells as well as an A-cell-rich culture, and studied 7B2 secretion under certain stimulations. 7B2 was secreted by isolated hamster pancreatic islet cells. This secretion was stimulated by theophylline and arginine, but glucose had a weak effect on the 7B2 secretion. Such a response of 7B2 to the stimulations was different from that of insulin or glucagon. 7B2 secretion was also noted in the A-cell-rich culture. These results suggest that 7B2 is secreted by both A- and B-cells of the hamster pancreatic islets and its secretion is regulated under certain conditions.