Cell adhesion molecules in adrenal medulla grafts: enhancement of chromaffin cell L1/Ng-CAM expression and reorganization of extracellular matrix following transplantation

Intracerebral adrenal medulla grafts have been used in human patients as an experimental treatment for Parkinson's disease, based on studies in animal models of this disorder. However, alterations in chromaffin cell properties after transplantation and the factors controlling graft survival are poorly understood. Since cell adhesion molecules (CAMs) are involved in regeneration and development of neural tissue in vivo and in vitro, the present study was undertaken to determine the expression of CAMs in adrenal medulla isografts. Fragments of rat adrenal medulla were implanted into the right lateral ventricle. The majority of grafts survived quite well, for up to 2 months (the longest studied period). The implanted chromaffin cells did not develop extensive processes. The cells retained tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) immunoreactivity, while phenylethanolamine N-methyltransferase (PNMT) expression was decreased. Surviving transplanted chromaffin cells showed enhancement and spreading of surface L1/Ng-CAM expression as compared to normal chromaffin cells in adrenal medulla. The implanted chromaffin cells demonstrated only partial conversion to neuronal phenotypes. These chromaffin cells did not develop extensive processes, but showed an enhancement of L1/Ng-CAM expression. Surviving chromaffin cells were accompanied by reorganization of their closely associated extracellular matrix (ECM). As compared to normal in situ adrenal medulla, graft ECM demonstrated a substantial increase of L1/Ng-CAM and laminin immunoreactivities and a distinct decrease in J1/tenascin expression. Some adrenal medulla grafts degenerated, particularly when misplaced within the host brain parenchyma. In these cases the grafts showed fragmentation of ECM and gradual disappearance of CAMs. These results suggest that surviving adrenal medulla grafts exhibit increased synthesis of certain CAMs by chromaffin cells, which may be involved in interactions between chromaffin cells and the surrounding ECM. It is speculated that both surviving and degenerating adrenal medulla grafts could provide CAMs and ECM components including laminin to host brain and this way contribute to functional effects of grafts.

Histogenesis of the human adrenal medulla. An evaluation of the ontogeny of chromaffin and nonchromaffin lineages

The authors previously evaluated the expression of a panel of chromaffin-related genes during histogenesis of the human adrenal medulla. In these studies, chromaffin and nonchromaffin adrenal neuroblasts were identified. To better characterize these nonchromaffin neuroblasts, the authors evaluated two additional markers: HNK-1, an antibody recognizing the migratory neural crest cell; and S-100, a protein expressed by sustentacular cells of the adrenal medulla. HNK-1 immunoreactivity was found in both chromaffin and nonchromaffin cell types at different times during development, marking the nonchromaffin lineage during the second trimester of gestation as well as the chromaffin lineage in the neonatal period. In addition, S-100 expression was noted in some nonchromaffin neuroblasts, and sustentacular cells were first identified at approximately 28 weeks of gestational age. These data suggest a model of human adrenal medullary histogenesis that incorporates the chromaffin, ganglionic, and sustentacular lineages known to constitute the adult adrenal medulla.

Bis-oxonol experiment on plasma membrane potentials of bovine adrenal chromaffin cells: depolarizing stimuli and their possible interaction

Changes of plasma membrane potential of isolated bovine adrenal chromaffin cells were monitored by fluorescent probe, bis-[1,3-diethyl-thiobarbiturate]trimethineoxonol (bis-oxonol), which responds to depolarization, resulting in increase of its fluorescence. Excess K+, gramicidin D, veratridine and ouabain all increased bis-oxonol fluorescence. Cells challenged with acetylcholine (ACh) or gamma-aminobutyric acid (GABA) produced a steady-state increase of bis-oxonol fluorescence, reflecting that averaged depolarization occurred continuously. Both effects were dependent on concentration with similar range, and mediated via nicotinic ACh receptor and GABAA receptor, respectively. Application of GABA with ACh or veratridine not only simultaneously but also pretreatedly caused an additive increment of bis-oxonol fluorescence. These results suggest that chromaffin cells in vitro reveal an additively enhanced change of plasma membrane potential in response to the combination of depolarizing stimuli.

Stimulation of Ca2(+)-independent catecholamine secretion from digitonin-permeabilized bovine adrenal chromaffin cells by guanine nucleotide analogues. Relationship to arachidonate release

The effect of GTP analogues on catecholamine secretion and [3H]arachidonic acid release from digitonin-permeabilized adrenal chromaffin cells was examined. Several GTP analogues stimulated Ca2(+)-independent exocytosis, with the order of efficacy being XTP greater than ITP greater than guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG) greater than guanosine 5'-[gamma-thio]triphosphate (GTP[S]). The stimulatory effect of the GTP analogues appeared to be due to activation of a conventional GTP-binding protein, as it was inhibited by guanosine 5'-[beta-thio]diphosphate (GDP[S]). In contrast, Ca2(+)-dependent exocytosis was only partially inhibited by high doses of GDP[S]. GTP did not stimulate Ca2(+)-independent exocytosis, but instead was found to inhibit secretion caused by micromolar Ca2+. Arachidonic acid (100 microM) also stimulated Ca2(+)-independent catecholamine secretion. Determination of the effect of GTP analogues on release of free [3H]arachidonic acid into the medium showed that it was stimulated by GTP[S] but inhibited by GTP, p[NH]ppG, ITP and XTP. The inhibition of [3H]arachidonic acid release by XTP was not prevented by GDP[S]. These results demonstrate that activation of a GTP-binding protein by certain GTP analogues can induce Ca2(+)-independent secretion in adrenal chromaffin cells and that the effect of GTP analogues on Ca2(+)-independent secretion can be dissociated from generation of arachidonic acid.

Mechanisms of toxicity and cellular resistance to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 1-methyl-4-phenylpyridinium in adrenomedullary chromaffin cell cultures

Bovine adrenomedullary chromaffin (BAMC) cells, cultured in a defined medium, were used to study the mechanisms of toxicity and cellular resistance to the catecholamine neuron toxicants 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium (MPP+). The viability of the cells was assessed biochemically [cellular catecholamine content and the catalytic activities of tyrosine hydroxylase (TH) and lactate dehydrogenase (LDH)] and anatomically (by electron microscopy). When cultures of BAMC cells were exposed to MPTP or MPP+ for 3 days, a marked loss of cellular catecholamines and TH activity was observed. The addition of an inhibitor of monoamine oxidase (MAO) B (Ro 19-6327), but not MAO A (clorgyline), prevented the toxicity of MPTP but not that of MPP+. In addition, the cellular toxicity of MPP+, but not MPTP, was antagonized by desmethylimipramine, an inhibitor of cellular catecholamine uptake. The toxicity of MPP+ was time dependent, with losses of TH and the release of cellular LDH occurring after 48 h in culture. Catecholamine depletion occurred somewhat sooner, being evident after 24 h of exposure to MPP+. The cellular toxicity of MPP+ was concentration dependent and significantly enhanced by inhibitors of catecholamine vesicular uptake (reserpine, tetrabenazine, or Ro 4-1284). Electron microscopic examination of cells treated with either MPP+, tetrabenazine, or their combination revealed that MPP+ damaged BAMC cells and that this damage was markedly potentiated by the inhibition of vesicular uptake by tetrabenazine. The concentration of glucose in the culture media of untreated cells slowly decreased as a function of time. The rate of glucose consumption was markedly accelerated by MPP+ treatment and the losses in cell TH and the release of LDH into the media were preceded by a 99% depletion of glucose from the media. In cultures not treated with MPP+, lactate accumulated in the media as a function of time. Addition of MPP+ to the media increased the formation of lactate, in a concentration-dependent manner. Reserpine pretreatment further enhanced the production of lactate in response to MPP+. Culturing cells in glucose-free medium greatly potentiated the effects of MPP+ on cellular TH and catecholamines. The toxicity observed after 3 days' exposure of BAMC cells to MPP+ could be prevented when the medium was replaced with fresh medium every 24 h. The effects of glucose deprivation and reserpine were observed to be additive. The ability of MPP+ to affect mitochondrial function is determined by the capacity of the storage vesicle to sequester the pyridinium, acting as a cytosolic "buffer."(ABSTRACT TRUNCATED AT 400 WORDS)

An immunohistochemical study of endocrine cells of the alimentary tract of the King's skink (Egernia kingii)

The gastrointestinal tract of the King's skink (Egernia kingii) was examined for the presence of fifteen regulatory peptides, two proteinases and an amine by immunohistochemical methods. Immunoreactivity was detected for somatostatin, gastrin, motilin, bovine pancreatic polypeptide, pepsinogen and serotonin, but not for avian pancreatic polypeptide, gastric inhibitory peptide, secretin, cholecystokinin, enteroglucagon, pancreatic glucagon, gastrin-releasing polypeptide, neurotensin, vasoactive inhibitory polypeptide, leu-enkephalin or chymosin. The six peptides detected in E. kingii have been previously found in the gastrointestinal tract of squamate reptiles; however, immunoreactivity for other peptides previously detected in squamates, in particular another skink, was not observed. In addition, chromogranin was found to be effective in the detection of endocrine cells though its specificity was unknown.

Effect of 5'-(N-ethylcarboxamido)adenosine on adenosine transport in cultured chromaffin cells

Extracellular adenosine is transported into chromaffin cells by a high-affinity transport system. The action of adenosine receptor ligands was studied in this cellular model. 5'-(N-Ethylcarboxamido)adenosine (NECA), an agonist of A2 receptors, activated adenosine transport. Km values for adenosine were 4.6 +/- 1.0 (n = 5) and 10.2 +/- 3.0 microM (n = 5) for controls and 100 nM NECA, respectively. The Vmax values were 66.7 +/- 23.5 and 170.2 +/- 30 pmol/10(6) cells/min for controls and 100 nM NECA, respectively. The A1 agonist N6-cyclohexyladenosine, the A1 antagonist 8-cyclopentyl-1, 3-dipropylxanthine, and the A1-A2 antagonist 1,3-dipropyl-8-(4-[(2-aminoethyl)amino]-carbonylmethyloxyphenyl)- xanthine did not significantly modify the adenosine transport in this system. Binding studies done with [3H]dipyridamole, a nucleoside transporter ligand, did not show changes in either the number or affinity of transporter sites after NECA treatment. This ligand can enter cells and quantifies the total number of transporters. The binding studies with [3H]-nitrobenzylthioinosine, which quantifies the plasma membrane transporters, showed a Bmax of 19,200 +/- 800 and 23,200 +/- 700 transporters/cell for controls and 100 nM NECA, respectively. No changes in the KD were obtained. The effects of NECA were not mediated through adenylate cyclase activation, because its action was not imitated by forskolin.

Mechanism of calcium transport across the plasma membrane of bovine chromaffin cells

The mechanism of calcium transport across the plasma membrane of chromaffin cells was studied using plasma membrane vesicles prepared from cells of adrenal medulla. Purification of the plasma membrane was about 30-fold, based on the alpha-bungarotoxin binding activity. The isolated membrane vesicles have both Na+/Ca2+ exchange and calcium pump activities. The Na+/Ca2+ exchange activity increased with the free calcium concentration and was not saturated at 1 mM, the highest concentration tried. The K1/2 of the calcium pump for calcium is 0.06 microM. Part of the Na+/Ca2+ exchange activity was inhibited by preincubation of the membrane vesicles with veratridine and the effect of veratridine was reversed by tetrodotoxin. The calcium taken up by the calcium pump was released by 0.005% saponin, but was not affected by oxalate. The calcium taken up by the calcium pump was released by exchanging with the external sodium, which suggests that the two calcium transport systems are located on the same population of membrane vesicles. The above evidence indicates that both calcium transport activities are located on the plasma membrane and not on contaminating organelle membranes. The significance of the two calcium transport systems in regulation of cytosolic calcium concentration of chromaffin cells is discussed.

Enhancement by GABA of the stimulation-evoked catecholamine release from cultured bovine adrenal chromaffin cells

The possible involvement of GABAergic mechanisms in the catecholamine (CA) release from adrenal medulla was investigated in a primary culture of bovine adrenal chromaffin cells. GABA elicited CA release and enhanced acetylcholine (ACh)-, excess K(+)- and veratridine-evoked CA release. Muscimol, a selective GABAA receptor agonist, mimicked the action of GABA on CA release. On the other hand, baclofen, a GABAB receptor agonist, failed to affect basal or evoked CA release. Furthermore, bicuculline and picrotoxin blocked the enhancement by GABA of veratridine-evoked CA release without affecting basal CA release and CA release evoked by veratridine. In Ca2(+)-free medium, GABA failed to affect basal and caffeine-evoked CA release. ACh-evoked CA release was slightly reduced by bicuculline, whereas excess K(+)-evoked CA release was not, suggesting the involvement of endogenous GABA in CA release evoked by ACh. These results suggest a facilitatory modulation by GABA of basal and evoked release of CA from bovine adrenal medulla through GABAA receptor-mediated mechanisms.

The sympathoadrenal lineage in avian embryos. I. Adrenal chromaffin cells lose neuronal traits during embryogenesis

Cells of the sympathoadrenal lineage, including sympathetic neurons, adrenal chromaffin cells (pheochromocytes), and small intensely fluorescent (SIF) cells, arise from the neural crest. We have used antisera against catecholamine biosynthesis enzymes in conjunction with the monoclonal antibody A2B5 and an antiserum against the 160-kDa neurofilament (NF) protein, as markers of neuronal differentiation, to characterize the ontogeny of the sympathoadrenal lineage in quail embryos. The precursors of sympathetic neurons and pheochromocytes, present in the primary sympathetic chains, express neuronal traits and tyrosine hydroxylase (TH) early in development. The precursors that enter the developing adrenal gland from the primary sympathetic chain lose neuronal traits and later express the enzyme phenylethanolamine N-methyltransferase (PNMT). No TH+ cells differentiate in cultures of early (E7) embryonic adrenal glands after all A2B5+ cells have been immunoablated. When transplanted onto the neural crest migratory pathway, cells present in older (E13) embryonic adrenal glands can give rise to NF+ cells in the sympathetic ganglia. We conclude that both sympathetic neurons and pheochromocytes in avian embryos arise from a common bipotential precursor that initially expresses neuronal traits.

Cyclic GMP regulates nicotine-induced secretion from cultured bovine adrenal chromaffin cells: effects of 8-bromo-cyclic GMP, atrial natriuretic peptide, and nitroprusside (nitric oxide)

Methacholine, atrial natriuretic peptide (ANP), nitroprusside (nitric oxide), angiotensin II, and bradykinin raised cyclic GMP (cGMP) levels in cultured bovine adrenal chromaffin cells. The role of cGMP in secretion from chromaffin cells was examined using 8-bromo-cGMP. This analogue had no effect on basal secretion or secretion due to angiotensin II, bradykinin, or a high K+ level but potentiated secretion due to low doses of nicotine. At supramaximal doses of nicotine, 8-bromo-cGMP inhibited secretion. These effects of 8-bromo-cGMP were not due to changes in the nicotine-induced rise in cytosolic calcium concentration. A potentiation of secretion due to low doses of nicotine was also found following simultaneous addition of ANP or nitroprusside, a result suggesting that ANP and nitric oxide (endothelium-derived relaxing factor) could be important regulators of secretion from adrenal chromaffin cells.

GABAergic modulation of catecholamine release from cultured bovine adrenal chromaffin cells. Evidence for the involvement of Cl(-)-dependent Ca2+ entry

The mode by which GABA facilitates the basal and stimulation-evoked catecholamine (CA) release from cultured bovine adrenal chromaffin cells was investigated. Muscimol, a GABAA receptor agonist, facilitated 45Ca uptake in a concentration-related manner. When GABA and acetylcholine (ACh) were simultaneously applied, additive increase in 45Ca uptake was observed. Similar effect on 45Ca uptake was observed in the presence of GABA and veratridine, although 45Ca uptake induced by a rather low concentration of veratridine was more than additively enhanced by GABA. GABA-evoked CA release was also more than additively enhanced by BayK 8644 whereas there was only an additive effect on 45Ca uptake. Substitution of extracellular Cl- by sucrose ("low Cl- medium") during the stimulation with GABA enhanced GABA-evoked CA release. Substitution of extracellular Cl- for more than 1 h abolished GABA-evoked CA release and 45Ca uptake. At this time, the concentration-response curve for veratridine-evoked CA release was shifted to left and GABA no longer enhanced veratridine-evoked CA release at any concentration of veratridine. GABA-induced facilitation of 45Ca uptake in the presence of low concentration of veratridine was also inhibited by long-term treatment with low Cl- medium. These results suggest that the Cl(-)-dependent process linked to GABAA receptor acts on voltage-sensitive Ca2+ channels in chromaffin cells to elicit and modulate CA release.

Prolonged analgesia by enkephalinase inhibition in rats with spinal cord adrenal medullary transplants

Transplants of adrenal medullary tissue or isolated chromaffin cells into the spinal cord subarachnoid space has been shown to reduce pain sensitivity in rats. This analgesia probably results from the release of neuroactive substances, particularly opioid peptides, from the transplanted cells since it is induced by nicotinic stimulation of chromaffin cell receptors, and can be blocked by naloxone. However, this analgesia is short-lived, most likely due to the rapid hydrolysis of opioid peptides. The purpose of this study was to determine whether protection of opioid peptide hydrolysis by the potent enkephalinase inhibitor kelatorphan could prolong this analgesia. Results indicated that the intrathecal injection of kelatorphan in animals with either adrenal medullary or chromaffin cell implants significantly prolonged nicotine-stimulated analgesia. Pretreatment with naloxone completely eliminated this analgesia. These results suggest that it may be possible to induce long-term reductions in pain sensitivity using enkephalinase inhibitors following the transplantation of opioid peptide-producing cells into the CNS.

The innervation of the adrenal gland. IV. Innervation of the rat adrenal medulla from birth to old age. A descriptive and quantitative morphometric and biochemical study of the innervation of chromaffin cells and adrenal medullary neurons in Wistar rats

The innervation of the adrenal medulla has been investigated in normal Wistar rats from birth to old age and ultrastructural findings compared with biochemical markers of the cholinergic innervation of the adrenal gland and catecholamine storage. Morphological evidence of the immaturity of the innervation during the first postnatal week is provided and using quantitative morphometry the innervation of chromaffin cells is shown to reach a mean total of 5.4 synapses per chromaffin cell during the period 26 days to 12 weeks of age. The variation in contents of synaptic profiles is discussed in the light of recent work that demonstrates a major sensory as well as visceral efferent innervation of the gland. Adrenal medullary neurons usually occur in closely packed groups, intimately associated with Schwann cells. Axodendritic and axosomatic synapses on these neurons are described and the likely origin of axonal processes innervating the neurons discussed. In old age the density of innervation remains the same as in young adult animals even though the medulla shows evidence of hyperplasia and hypertrophy of individual chromaffin cells.

Early fetal acquisition of the chromaffin and neuronal immunophenotype by human adrenal medullary cells. An immunohistological study using monoclonal antibodies to chromogranin A, synaptophysin, tyrosine hydroxylase, and neuronal cytoskeletal proteins

The development of chromaffin and neuronal features in the adrenal medulla was studied in normal human fetuses with gestational ages (GAs) of 6-34 weeks. Monoclonal antibodies specific for chromogranin A, synaptophysin, and tyrosine hydroxylase; for different subunits and phosphoisoforms of neurofilament (NF) proteins; and for microtubule-associated proteins were applied. Morphologically, two major cell types could be distinguished, i.e., "large" cells with pale nuclei and ill-defined cytoplasm, which were present from 9 weeks GA on, and clusters of "small," primitive appearing cells, present from 14 weeks GA on. The large cells were immunoreactive for chromogranin A, synaptophysin, tyrosine hydroxylase, and NF proteins, similar to adult chromaffin cells. In contrast, small cells expressed NF proteins and tyrosine hydroxylase, but not chromogranin A or synaptophysin, more resembling ganglion cells in the adult adrenal medulla. At the latest developmental stages large cells were observed in the center of the clusters of "small" cells, which morphologically resembled immature ganglion cells and expressed NF proteins in their perikarya. These observations indicate that chromaffin and ganglion cells establish their immunophenotype early in embryogenesis. They suggest that "large" and "small" cells are progenitors of the chromaffin and the ganglion cells, respectively, of the mature adrenal medulla.

Arachidonic acid liberated by diacylglycerol lipase is essential for the release mechanism in chromaffin cells from bovine adrenal medulla

Chromaffin cells from bovine adrenal medulla secrete catecholamines on stimulation with acetylcholine. In addition to the activation of the phosphatidylinositol cycle, arachidonic acid is generated, which was thought to be the result of phospholipase A2 activation. We have demonstrated in isolated plasma membranes of these cells that arachidonic acid is generated by a two-step reaction of diacylglycerol and monoacylglycerol lipase splitting diacylglycerol, which originates from the action of phospholipase C on phosphatidylinositols. No phospholipase A2 activity could be detected in plasma membranes so far. External addition of arachidonic acid increases the release in the absence and in the presence of agonist. Inhibition of the diacylglycerol lipase by RHC 80267 suppresses the catecholamine release, which is restored on addition of arachidonic acid. This effect, however, is reversed by lipoxygenase inhibitors, indicating that it is not arachidonic acid itself, but one of its lipoxygenase products, that is essential for inducing exocytosis.

Substrate dependency of neurite outgrowth from adult human chromaffin cells. Inhibitory effects of human brain tissue

Attempts to treat Parkinson's disease with grafts of chromaffin cells to the caudate nucleus have recently generated considerable interest. However, it is not known whether chromaffin cells can innervate the human central nervous system. We have directly addressed this question by measuring neurite outgrowth in cultures of normal adult human chromaffin cells on frozen sections of caudate nucleus and other substrates, a technique previously employed in animal studies. Chromaffin cells from radical nephrectomies were plated on frozen sections of caudate nucleus and heart, and on polylysine-coated slides, and were maintained for up to 3 weeks in medium with nerve growth factor to induce neurite outgrowth and cytosine arabinoside to prevent proliferation of other cell types. Additional cultures maintained for up to 3 weeks in nerve growth factor without tissue sections were trypsinized to remove processes and replated on frozen sections or polylysine to evaluate process regeneration. Processes were quantitated after visualization by glyoxylic acid-induced fluorescence. No more than 14% of cell clusters formed processes longer than 100 microns on caudate nucleus, versus 24% on heart and up to 84% on polylysine (all p less than .01). Comparable patterns were obtained for neurite regeneration. Our findings suggest that human brain tissue is for the most part inhospitable to neurites produced by sympathoadrenal cells, and that even tissues normally innervated by such cells are less hospitable than synthetic substrates. These findings might have important implications for future studies related to chromaffin cell transplantation.

Studies on the effect of insulin-like growth factor-I on catecholamine secretion from chromaffin cells

Chromaffin cells cultured in serum-free medium secreted a smaller percentage of their catecholamine stores in response to stimulation by high K+ (55 mM) than did cells cultured in serum-containing medium. Addition of insulin-like growth factor-I (IGF-I) to serum-free medium restored high K(+)-stimulated catecholamine secretion to the levels seen in serum-treated cultures. In contrast, addition of IGF-I to serum-containing medium had little effect on catecholamine secretion. These results suggest that serum contains IGF-I or another factor that maintains the secretory responsiveness of chromaffin cells. IGF-I not only enhanced high K(+)-stimulated catecholamine secretion, but also augmented secretion elicited by the nicotinic agonist dimethyl-phenylpiperazinium, the dihydropyridine agonist Bay K 8644, and Ba2+. IGF-I did not affect the dependence of catecholamine secretion on extracellular Ca2+ concentration nor did it affect the time course of secretion. Experiments using 45Ca2+ demonstrated that IGF-I treatment enhanced Ca2+ uptake into the cells. When cells were permeabilized by treatment with digitonin, Ca2(+)-dependent catecholamine secretion was slightly, but consistently, greater from IGF-I-treated cells than from untreated cells. Our results suggest that IGF-I may enhance catecholamine secretion partly by increasing Ca2+ entry into the cells and partly by affecting a step distal to Ca2+ entry.

Separation and culture of living adrenaline- and noradrenaline-containing cells from bovine adrenal medullae

Separation of viable adrenaline-containing from noradrenaline-containing chromaffin cells in large amounts has been achieved. The procedure involves collagenase digestion of bovine adrenomedullary tissue, isolation of cells through gentle filtration, separation of chromaffin from nonchromaffin cells on discontinuous gradients of the radiopaque contrast Renografin, and separation of adrenaline-enriched from noradrenaline-enriched fractions after centrifugation on self-generated Percoll gradients. Collection of 1-ml Percoll fractions gave two clear-cut catecholamine peaks. The denser peak was enriched in adrenaline and phenylethanolamine-N-methyltransferase (PNMT), suggesting that over 90% of cells were adrenergic. The lighter peak was preferentially enriched in noradrenaline but not in PNMT. With this information, we could collect by gentle aspiration two main fraction layers of larger volumes; one at the bottom of the Percoll gradient, which contained essentially adrenaline-storing cells and the other at the top of the gradient, enriched in noradrenaline cells. Those cells could be maintained viable for at least 1 week in primary monolayer cultures, as shown by neutral red staining and trypan blue exclusion. This method will allow the identification of chemical components, receptors, or ionic channels present in one specific type of cell, to determine their relevance to the regulation of the differential secretion of specific materials present in one but not in the other cell type and to ascertain whether the released materials from one cell type affect the functions of the other.

Effect of quinine on the release of catecholamines from bovine cultured chromaffin cells

1. The effects of quinine on catecholamine release from cultured bovine chromaffin cells were studied. 2. Quinine (25-400 microM) produced a dose-related inhibition of catecholamine release in response to depolarizing concentrations (12.5-50 mM) of K+. 3. The inhibition of the secretory response to high K+ produced by quinine decreased with the increase in the extracellular concentration of Ca2+. 4. Stimulation of cultured chromaffin cells with 50 mM K+ produced a significant increase in Ca2+ influx. In the presence of 100 microM quinine a 54% inhibition of the K(+)-induced Ca2+ influx was observed. 5. Quinine treatment of chromaffin cell cultures produced a small but significant decrease in membrane resting potential and a less pronounced depolarization in response to 50 mM K+. 6. The results suggest that the inhibition of the K(+)-evoked release of catecholamines produced by quinine is at least partly due to a decrease in Ca2+ influx. Ca2+ influx is lower because quinine reduces the sensitivity of the membrane potential to changes in extracellular K+ but direct effects of quinine on Ca2+ channels cannot be excluded.

Serum gastrin concentration affects the self replication rate of the enterochromaffin like cells in the rat stomach

The influence of antrectomy and antrum exclusion on the enterochromaffin like cell kinetics in the gastric mucosa of the rat was studied using a combination of histamine immunocytochemistry and autoradiography after in vivo labelling with tritiated thymidine. In all experimental groups, the enterochromaffin like cells were found to incorporate the DNA precursor, thus indicating an ability to divide. The serum gastrin concentration was raised by antrum exclusion and reduced by antrectomy. After antrum exclusion, the enterochromaffin like cell proliferation rate increased as indicated by a doubling of the labelling index and by the resulting enterochromaffin like cell hyperplasia (after six weeks). After antrectomy, the enterochromaffin like cell labelling index decreased to reach 25% of the control value; at this time the enterochromaffin like cell density had not decreased significantly. The observed correlation between the enterochromaffin like cell labelling indices and the serum gastrin concentration supports the hypothesis that enterochromaffin like cell proliferation is influenced by serum gastrin.

Different patterns of agonist-stimulated increases of 3H-inositol phosphate isomers and cytosolic Ca2+ in bovine adrenal chromaffin cells: comparison of the effects of histamine and angiotensin II

Bovine adrenal chromaffin cells (BCC) were used to compare histamine- and angiotensin II-induced changes of inositol mono-, bis-, and trisphosphate (InsP1, InsP2, and InsP3, respectively) isomers, intracellular free Ca2+ ([Ca2+]i), and the pathways of inositol phosphate metabolism. Both agonists elevated [Ca2+]i by 200 nM 3-4 s after addition, but afterwards the histamine response was much more prolonged. Histamine and angiotensin II also produced similar four- to fivefold increases of Ins(1,4,5)P3 that peaked within 5 s. Over the first minute of stimulation, however, Ins(1,4,5)P3 formation was monophasic after angiotensin II, but biphasic after histamine, evidence supporting differential regulation of angiotensin II- and histamine-stimulated signal transduction. The metabolism of Ins(1,4,5)P3 by BCC homogenates was found to proceed via (a) sequential dephosphorylation to Ins(1,4)P2 and Ins(4)P, and (b) phosphorylation to inositol 1,3,4,5-tetrakisphosphate, followed by dephosphorylation to Ins(1,3,4)P3, Ins(1,3)P2, and Ins(3,4)P2, and finally to Ins(1 or 3)P. In whole cells, Ins(1 or 3)P only increased after histamine treatment. Additionally, Ins(1,3)P2 was the only other InsP2 besides Ins(1,4)P2 to accumulate within 1 min of agonist treatment [Ins(3,4)P2 did not increase]. These results support a correlation between the time course of Ins(1,4,5)P3 formation and the time course of [Ca2+]i transients and illustrate that Ca2(+)-mobilizing agonists can produce distinguishable patterns of inositol phosphate formation and [Ca2+]i changes in BCC. Different patterns of second-messenger formation are likely to be important in signal recognition and may encode agonist-specific information.

Identification of a functional glucocorticoid response element in the phenylethanolamine N-methyltransferase promoter using fusion genes introduced into chromaffin cells in primary culture

The rat gene encoding phenylethanolamine N-methyltransferase (PNMT) was cloned and a consensus sequence for a glucocorticoid response element (GRE) was found at -513 bp, 5' to the transcriptional start site. In order to define the function of this element, fusion genes containing the PNMT promoter and a chloramphenicol acetyltransferase (CAT) reporter gene were constructed. These constructs did not express after transfection into any of 7 continuous cell lines, none of which endogenously produce PNMT. A system for transfecting chromaffin cells in primary culture was therefore devised using constructs containing 200 bp of the proenkephalin (ENK) promoter, whose expression characteristics are well known. pENK beta GAL-1, containing the ENK promoter with a lac Z reporter, was introduced into these cells and beta-galactosidase activity was visualized in situ. Approximately 90% of cells transfected were chromaffin; transfection efficiency was 5%. High levels of CAT activity were measured in chromaffin cells transfected with pENKAT12, possessing a CAT reporter. In contrast to tumor cell lines, pENKAT12 induction in these cells by forskolin and phorbol esters did not require a phosphodiesterase inhibitor. In this chromaffin system, both basal and regulated expression of the PNMT fusion genes were detected. Dexamethasone (dex) induced expression of pPNMT3000 and pPNMT900, containing the putative GRE and 3000 bp or 863 bp of PNMT promoter sequence, 4- to 10-fold. Expression of pPNMT300 and pPNMT100, which lack the GRE and contain 273 bp or 99 bp of PNMT promoter sequence, was unaffected by dex. Addition of the PNMT region spanning -490 to -863 bp conferred full dex responsiveness to a thymidine kinase promoter. Deletion of the putative GRE sequence by site-directed mutagenesis abolished the dex response. These data identify the sequence at -513 bp in the rat PNMT gene as a functional, positively acting GRE. Primary cultures of bovine chromaffin cells provide a biologically relevant expression system for transcriptional studies of catecholamine genes and their related neuropeptides.