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

"In vitro" effect of GM1 ganglioside on adrenal chromaffin cells

Exposure of "in vitro" grown immature and adult adrenal chromaffin cells to concentrations of 10(-3) or 10(-5) M but not 10(-7) M GM1 ganglioside, resulted in significant increase in cell diameter, coupled with reduction of adhesion to substrate within 48 hrs of exposure. None of the GM1 concentrations, with or without serum supplementation, did significantly increase neuritogenesis in chromaffin cells. Immature chromaffin cells underwent neuritogenesis when grown in co-cultures with actively growing astroglia from striatum or cerebral cortex, an effect that was potentiated by NGF administration and blocked by anti-NGF. In neither of the former conditions did 10(-6) M GM1 prove to increase the number of neurite emitting cells nor their mean neuritic length further. It is speculated that GM1 does not perform the neuritogenic role described for central neurons in chromaffin cells, nor does it potentiate NGF effect on neuritogenesis observed in other peripheral neurons.

Diadenosine 5',5"-P1,P4-tetraphosphate (Ap4A), ATP and catecholamine content in bovine adrenal medulla, chromaffin granules and chromaffin cells

The level of diadenosine 5',5"-P1-P4-tetraphosphate (diadenosine tetraphosphate or Ap4A), catecholamines, ATP and other nucleotides has been investigated in perchloric acid extracts of bovine adrenal medulla, chromaffin granules and cultured chromaffin cells. As a control, the amount of Ap4A and ATP has also been measured in human blood platelets. The following values (nmol/mg protein) were found in adrenal medulla: Ap4A, 0.019 +/- 0.004; ATP, 109 +/- 11; ADP, 23.8 +/- 5.8; AMP, 11.3 +/- 1.5; p4A, 0.18 +/- 0.08; catecholamines, 460 +/- 57. The level of Ap4A, catecholamines and ATP (nmol/mg protein) found in chromaffin granules and in chromaffin cells were, respectively: (0.15 +/- 0.07; 2175 +/- 99; 531 +/- 66) and (0.22 +/- 0.14; 1143 +/- 277; 222 +/- 53). In all the cases investigated, the ratio catecholamines/ATP and catecholamines/Ap4A were around 5 and in the order of 10(3), respectively. The amount of Ap4A found here, in bovine adrenal medulla, chromaffin granules and chromaffin cells, is two orders of magnitude lower than previously reported.

omega-Agatoxin-IVA-sensitive calcium channels in bovine chromaffin cells

A large component of the whole-cell currents through Ca2+ channels in bovine adrenomedullary chromaffin cells has been shown to be insensitive to both L-type and N-type Ca2+ channel blockers, suggesting the existence of a third type of Ca2+ channel. In the present paper, omega-agatoxin-IVA (AgTx), a selective blocker of P-type Ca2+ channels in mammalian neurons, has been used to investigate the presence of this subtype of Ca2+ channel in bovine chromaffin cells. Barium currents (IBa) through Ca2+ channels were recorded in whole-cell patch-clamped bovine chromaffin cells. IBa was blocked by AgTx in a dose-dependent and irreversible manner. At the maximal concentration used (1 microM), AgTx inhibited IBa by 49.5 +/- 3%. Such a blockade was also present when bovine chromaffin cells were pretreated with 10 microM furnidipine, a novel 1,4-dihydropyridine L-type channel blocker, and after treatment with 1 microM of the N-type channel blocker, omega-conotoxin GVIA (CgTx). A combination of these three types of Ca2+ channel blockers suppressed the macroscopic Ba2+ currents by 88%. We conclude that bovine chromaffin cells, in addition to N- and L-type Ca2+ channels, possess a P-like component in their whole-cell currents through the Ca2+ channels.

The mechanism of Ba(2+)-induced exocytosis from single chromaffin cells

Dialysis of Ba2+ into voltage-clamped single bovine chromaffin cells produced a concentration-dependent increase in cell capacitance, reflecting an enhanced rate of exocytotic events. Between 0.1 and 1 mM, Ba2+ linearly increased both the rate and the total amount of exocytosis. In unclamped cells also, extracellular Ba2+ induced the release of catecholamines, as assayed with a carbon-fibre electrode in the amperometric mode. Additionally, extracellular application of Ba2+ increased the apparent internal Ca2+ concentration ([Ca2+]app) in fura-2-loaded chromaffin cells. These observations were made both in the presence and absence of external Ca2+ (Cao2+), as well as after depletion of the intracellular Ca2+ stores with ionomycin. Under current-clamp conditions, Ba2+ induced pronounced depolarization of the cells. These results are compatible with the following conclusions: by blocking K+ channels, Ba2+ causes depolarization of chromaffin cells. This results in opening of voltage-gated Ca2+ channels and Ba2+ entry into the cytosol. Ba2+ then directly triggers exocytotic events, although it induces exocytosis only at concentrations more than a 100-fold higher than Ca2+. Various effects contribute to the generally observed greater secretory responses with Ba2+ as compared with Ca2+; these are the depolarizing effects of extracellular Ba2+, its greater entry through non-inactivating Ca2+ channels and its poor intracellular buffering largely arising from its weak affinity for plasmalemmal Ca2+ extrusion mechanisms. In some cases, Ba2+ additionally induces release of Ca2+ from internal stores, as evidenced by its effect on fura-2 fluorescence at different wavelengths.

A Ca-dependent early step in the release of catecholamines from adrenal chromaffin cells

Intense stimuli, such as trains of depolarizing pulses or the caffeine-induced release of calcium from intracellular stores, readily depress the secretory response in neuroendocrine cells. Secretory responses are restored by rest periods of minutes in duration. This recovery was accelerated when the concentration of cytosolic calcium was moderately increased and probably resulted from calcium-dependent replenishment of a pool of release-ready granules. Continuously increased concentrations of calcium led the over-filling of such a pool. Subsequently, secretory responses to stronger calcium stimuli were augmented. Hormone-induced calcium transients with a plateau phase of increased concentration of calcium may enhance the secretory response in this way.

R56865 inhibits catecholamine release from bovine chromaffin cells by blocking calcium channels

1. The effects of R56865 (a new class of cardioprotective agent which prevents Na+ and Ca2+ overload in cardiac myocytes) on catecholamine release, whole-cell current through Ca2+ channels (IBa) and cytosolic Ca2+ concentrations, [Ca2+]i, have been studied in bovine chromaffin cells. 2. R56865 caused a time- and concentration-dependent blockade of catecholamine release from superfused cells stimulated intermittently with 5 s pulses of 59 mM K+. After 5 min superfusion, a 3 microM concentration inhibited secretion by 20%; the blockade increased gradually with perfusion time, to reach 85% after 40 min. The IC50 to block secretion after 5 min periods of exposure to increasing concentrations of R56865 was around 3.1 microM. The blocking effects of R56865 were reversible after 5-15 min wash out. In high Ca2+ solution (10 mM Ca2+), the degree of blockade of secretion diminished by 20% in comparison with 1 mM Ca2+. 3. In electroporated cells, R56865 (10 microM) did not modify the secretory response induced by the application of 10 microM free Ca2+. 4. R56865 blocked the peak IBa current in a concentration- and time-dependent manner; its IC50 was very similar to that obtained for secretion (3 microM). The compound not only reduced the size of the peak current but also promoted its inactivation; when the effects of R56865 were measured at the most inactivated part of the current, its IC50 was 1 microM. Both the inactivation and the reduction of the peak currents were reversible upon washing out the drug. 5. In fura-2-loaded single chromaffin cells the basal [Ca2+]i of around 100 nM was elevated to a peak of1.5 microM by the application of a 5 s pulse of 59 mM K+. R56865 (10 microM) did not affect the basal [Ca2+]but blocked by 90% the K+-evoked increase. This effect was fully reversible after 5-10 min of wash out.6. The results are compatible with the idea that R56865 blocks Ca2+ entry into K+-depolarized chromaffin cells by promoting the inactivation of voltage-dependent Ca2+ channels; this would lead to the limitation of the rise in [Ca2+]i and of the release of catecholamines. The restriction of catecholamine release may favour indirectly the known direct beneficial cardioprotective actions of R56865.

The nicotinic acetylcholine receptor of the bovine chromaffin cell, a new target for dihydropyridines

The effects of 1,4-dihydropyridine derivatives on divalent cation transients and catecholamine release stimulated by either high K+ or the nicotinic receptor agonist dimethyl-phenyl-piperazinium (DMPP) have been compared in bovine adrenal chromaffin cells. The activation of Ca2+ entry pathways was followed by measuring 45Ca2+ or Mn2+ uptake, or by the changes of [Ca2+]i in fura-2-loaded chromaffin cells. Various dihydropyridine Ca2+ channel blockers (nimodipine, PCA50938, nifedipine, nitrendipine, furnidipine) abolished the DMPP-mediated effects, but prevented only partially the activation by high [K+]0 of 45Ca2+ uptake. The IC50 for DMPP-induced activation was around 1 microM. The L-type Ca2+ channel activator Bay K 8644 potentiated the uptake of 45Ca2+ induced by K+ depolarization at concentrations between 10 nM and 1 microM, but completely inhibited the uptake of 45Ca2+ by DMPP (IC50, 0.9 microM). Both high [K+]0 and DMPP produced membrane depolarization as measured using bis-oxonol. The DMPP-evoked, but not the K(+)-evoked membrane depolarization was prevented by Na+ removal, suggesting that the depolarization was due to Na+ entry through the acetylcholine receptor ionophore. Nimodipine at 10 microM abolished the depolarization induced by DMPP, leaving the K(+)-evoked depolarization unaffected. Tetrodotoxin (2 microM) did not affect the DMPP- or high K(+)-mediated cell depolarization. Whole-cell inward current evoked by 100 microM DMPP (IDMPP) was measured in cells voltage-clamped at -80 mV. Nimodipine (10 microM) reduced IDMPP by 36%; Bay K 8644 (10 microM) inhibited IDMPP by 67%. DMPP-evoked catecholamine release from superfused chromaffin cells was reduced by over 90% with 10 microM nimodipine; in contrast, K(+)-evoked release was decreased by 20%.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP modulation of calcium channels in chromaffin cells

1. The effects of externally applied micromolar concentrations of adenosine 5'-triphosphate (ATP) on Ca2+ currents (ICa) were studied in whole-cell clamped adrenaline-secreting chromaffin cells. 2. Ca2+ currents in chromaffin cells activated at about -40 mV, reached a maximum at 0 mV and had an apparent reversal potential at +50 to +60 mV, indicating the existence of only high voltage-activated Ca2+ channels. 3. ATP blocked Ca2+ current rapidly, reversibly and in a concentration-dependent manner (10(-9)-10(-4) M). 4. ATP did not completely block Ca2+ current even at the highest concentrations used (100 microM). The remaining component of Ca2+ current was characterized by slower activation and inactivation kinetics. 5. ATP blocked ICa even in the presence of nisoldipine and/or omega-conotoxin GVIA, suggesting that its modulatory role is not specific for L- and/or N-type Ca2+ channels. 6. Other adenine nucleotides also blocked the Ca2+ current partially. The order of potencies was ATP > or = ADP > AMP >> adenosine, indicating that the ATP effects are most probably mediated by a P2-type purinergic receptor. 7. Dialysis of the cells with an intracellular solution containing 1 mM guanosine 5'-O-thiodiphosphate (GDP-beta-S) or pre-incubation of the cells with pertussis toxin (PTX) blocked the inhibitory effects of ATP. 8. Intracellular application of the non-hydrolysable GTP analogue guanosine 5'-O-(3'-thiotriphosphate) (GTP-gamma-S; 50 microM) also decreased ICa in a manner similar to that seen for ATP and significantly reduced the ATP inhibitory effect. 9. Conditioning pulses to potentials positive to +80 mV partly reversed the inhibitory effects of ATP on the Ca2+ current. The prepulse-induced enhancement of ICa depended on [GTP]i-related G protein activity such that concentrations larger than 200 microM GTP, or GTP-gamma-S (50 microM) were required for significant prepulse potentiation of the Ca2+ current, while dialysis with GDP-beta-S prevented it. 10. We conclude that the ATP, co-released with catecholamines in the intact adrenal gland, may inhibit the secretory process by down-regulating the Ca2+ channel via a P2-type purinergic receptor coupled to a PTX-sensitive G protein.

Histamine evokes greater increases in phosphatidylinositol metabolism and catecholamine secretion in epinephrine-containing than in norepinephrine-containing chromaffin cells

Chromaffin cells have H1 histamine receptors. Histamine, acting at these receptors, increases the metabolism of inositol-containing phospholipids and stimulates catecholamine secretion from chromaffin cells. We have investigated the effects of histamine and other agents on the accumulation of inositol monophosphate (InsP1) and catecholamine secretion in purified cultures of norepinephrine-containing and epinephrine-containing bovine chromaffin cells. Histamine-stimulated InsP1 accumulation in epinephrine cells was three times greater than that in norepinephrine cells. In contrast, bradykinin caused roughly equivalent increases in InsP1 accumulation in the two chromaffin cell subtypes. Histamine-stimulated catecholamine secretion was also greater in epinephrine cells than in norepinephrine cells, whereas high K+, bradykinin, phorbol 12,13-dibutyrate, and angiotensin II all caused greater secretion from norepinephrine cells than from epinephrine cells. The density of H1 receptors in epinephrine cells was approximately three times greater than that in norepinephrine cells. The greater density of H1 receptors on epinephrine cells may account for the greater effects of histamine on InsP1 accumulation and catecholamine secretion in these cells.

Separation between cytosolic calcium and secretion in chromaffin cells superfused with calcium ramps

This paper describes experiments in which cytosolic Ca2+ concentrations ([Ca2+]i) and catecholamine release were measured in two populations of chromaffin cells stimulated with a solution enriched in K+ (100 mM). Once depolarized, external Ca2+ or Ba2+ ions were offered to cells either as a single 2.5 mM step or as a ramp that linearly increased the concentration from 0 to 2.5 mM over a 10-min period. A clear separation between the changes of the [Ca2+]i and the time course of secretion was observed. Specifically, secretion and [Ca2+]i rose in parallel when a Ca2+ step was used to reach a peak in a few seconds; however, while secretion declined to the basal level, [Ca2+]i remained elevated at a plateau of 400 nM. With a Ca2+ ramp, only a transient small peak of secretion was observed, yet the [Ca2+]i remained elevated throughout the 10-min stimulation period. The separation between secretion and [Ca2+]i was observed even when voltage-dependent Ca2+ channels were expected to remain open (mild depolarization in the presence of 1 microM Bay K 8644). By using Ba2+ steps or ramps, sustained noninactivating secretory responses were obtained. The results suggest that the rate and extent of secretion are not a simple function of the [Ca2+]i at a given time; they are compatible with the following conclusions: (i) A steep extracellular-to-cytosolic Ca2+ gradient is required to produce a sharp increase in the [Ca2+]i at exocytotic sites capable of evoking a fast but transient secretory response. (ii) As a result of Cai(2+)-dependent inactivation of Ca2+ channels, those high [Ca2+]i are possible only at early times after cell depolarization. (iii) The Cai(2+)-dependent supply of storage granules to the secretory machinery cooperates with the supply of Ca2+ through Ca2+ channels to regulate the rate and extent of secretion.

Nicotinic agonists, phorbol esters, and growth factors activate two extracellular signal-regulated kinases, ERK1 and ERK2, in bovine chromaffin cells

Treatment of bovine chromaffin cells with nicotinic agonists, phorbol esters, and growth factors increases protein kinase activity toward microtubule-associated protein-2 and myelin basic protein (MBP) in vitro. To characterize the kinases that are activated by these agents, we separated chromaffin cell proteins by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels into which MBP had been incorporated, allowed the proteins to renature, and then assayed MBP kinase activity by incubating the gels with [gamma-32P]ATP. Chromaffin cells contain a family of kinases that phosphorylate MBP in vitro. Two of these kinases, of M(r) 46,000 and 42,000 (PK46 and PK42), were activated by treatment of the cells with dimethylphenylpiperazinium (DMPP), phorbol 12,13-dibutyrate (PDBu), or insulin-like growth factor I (IGF-I). Activation of PK46 and PK42 by DMPP was dependent on extracellular Ca2+, whereas the effects of PDBu and IGF-I were Ca2+ independent. Down-regulation of protein kinase C by incubation of the cells with PDBu abolished the activation of PK46 and PK42 by DMPP, PDBu, and IGF-I. Staurosporine, a protein kinase C inhibitor, prevented the activation of PK46 and PK42 by DMPP and PDBu but did not block the activation of these kinases by IGF-I. Immunoblotting experiments with antiphosphotyrosine (anti-PTyr) antibodies demonstrated that agents that increased the kinase activities of PK46 and PK42 also increased the apparent PTyr content of M(r) 46,000 and 42,000 proteins. PK46 and PK42 comigrated with proteins that reacted with antibodies against extracellular signal-regulated kinases (ERKs). Thus, PK46 and PK42 appear to be the bovine homologues of ERK1 and ERK2.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscarinic acetylcholine receptor enhances phosphatidylcholine hydrolysis via phospholipase D in bovine chromaffin cells in culture

Although it is well-established that inositol-containing lipids serve as precursors of intracellular second messenger molecules in chromaffin cells, we describe some findings that show the formation of diacylglycerol from phosphatidylcholine in response to agonist-mediated stimulation. Stimulation of chromaffin cells by acetylcholine produced a high turnover of phosphatidylcholine, as suggested by the release of [3H]choline derived from [3H]-phosphatidylcholine in experiments performed with [3H]choline chloride-prelabeled cells. An enhanced breakdown of phosphatidylcholine was also inferred from the finding of an increased formation of [3H]diacylglycerol in chromaffin cells prelabeled with [3H]glycerol. The diacylglycerol mass that accumulated after stimulation showed a distinct temporal course and seemed to exceed the mass that has been reported to be derived from phosphatidylinositol. In keeping with the purported origin from phosphatidylcholine, diacylglycerol showed a high content in [3H]oleate molecular species. Phospholipase D activity measurements and experiments performed in the presence of propranolol (an inhibitor of phosphatidic acid:phosphohydrolase) suggested that phosphatidylcholine is hydrolyzed by a phospholipase D activity, producing phosphatidic acid, which is subsequently degraded to diacylglycerol, rather than by a phospholipase C. Incubation of chromaffin cells in the presence of atropine before addition of acetylcholine showed complete inhibition of the increased formation of [3H]-diacylglycerol, whereas d-tubocurarine failed to do so. Taken together, these results suggest that acetylcholine activates phosphatidylcholine breakdown and diacylglycerol formation in chromaffin cells via a muscarinic-type receptor.

Phorbol esters cause preferential secretion of norepinephrine from bovine chromaffin cells

Differential secretion of norepinephrine and epinephrine was studied in cultured bovine chromaffin cells. Nicotinic agonists and 55 mM K+ evoked a slightly greater release of norepinephrine than of epinephrine: The percentage of norepinephrine secreted was 1.5 to two times greater than the percentage of epinephrine secreted. In contrast, when the cells were treated with phorbol 12,13-dibutyrate, the percentage of norepinephrine released was six to eight times greater than that of epinephrine released. Similar results were obtained in experiments with cultures highly enriched in either norepinephrine-containing cells or epinephrine-containing cells. In response to 55 mM K+, catecholamine release from norepinephrine-containing cells was two times greater than that from epinephrine-containing cells. In response to phorbol 12,13-dibutyrate, secretion from norepinephrine-containing cells was 13 times greater than that from epinephrine-containing cells. These results suggest that protein kinase C plays a specific role in the regulation of catecholamine secretion from norepinephrine-containing cells.

Muscarinic receptors in separate populations of noradrenaline- and adrenaline-containing chromaffin cells

We have performed binding experiments of (a)[3H]quinuclidinyl benzilate to partially purified membranes from noradrenaline- and adrenaline-containing chromaffin cells and (b) [3H]N-methyl-quinuclidinyl benzilate to acutely isolated, or 48-h cultured, chromaffin cells subpopulations. Using this approach, we obtained enough evidence to conclude (1st) that muscarinic receptors are present in both noradrenaline- and adrenaline containing cells; (2nd) that noradrenaline cells contain in fact 2-3 fold higher density of those receptors; and (3rd) that those receptors undergo plastic changes upon chronic culturing of the cells.

Alamethicin channel permeation by Ca2+, Mn2+ and Ni2+ in bovine chromaffin cells

Alamethicin causes a concentration-dependent increase of [Ca2+]i in suspensions of bovine adrenal chromaffin cells loaded with fura-2. The basal levels of Cai2+ (234 +/- 37 nM; n = 4) increased to a maximum of 2347 +/- 791 nM (n = 3) with 100 micrograms/ml alamethicin. In the presence of 1 mM Cae2+ the increase reached a plateau within about 2-5 s. This increase was due to Ca2+ entry into chromaffin cells, since in the absence of Cae2+ alamethicin did not modify [Ca2+]i. This contrasts with ionomycin (1 microM) which produced a Cai2+ transient even in the absence of Cae2+. Mn2+ ions also entered chromaffin cells in the presence of alamethicin, as measured by the quenching of fura-2 fluorescence following excitation at 360 nm. Resting chromaffin cells had a measurable permeability to Mn2+ which was drastically increased by cell depolarization by K+ (50 mM) addition. This suggests that Mn2+ is able to permeate voltage-dependent Ca2+ channels. Ni2+ uptake into either resting or K(+)-stimulated chromaffin cells was undetectable, but addition of alamethicin induced rapid uptake of this cation. The alamethicin-induced entry of Ni2+ was decreased by 50 mM K+. Overall, the results are compatible with the formation by alamethicin of ion channels in chromaffin cell plasma membranes.

Separation of two pathways for calcium entry into chromaffin cells

1. The effects of various drugs on 45Ca + 40Ca uptake into cultured bovine adrenal chromaffin cells evoked by 1,1-dimethyl-4-phenylpiperazinium (DMPP) or high K, were studied. In the presence of 1 mM external 40Ca, with 45Ca as a radiotracer, unstimulated cells took up an average of 0.13 fmol/cell 40Ca and 772 c.p.m./10(6) cells of 45Ca (n = 76). Upon stimulation with DMPP (100 microM for 60 s) or K (59 mM for 60 s), Ca uptake increased to 0.92 and 1 fmol/cell, respectively. 2. Flunarizine behaved as a potent blocker of both DMPP- and K-evoked Ca uptake (IC50 of 1.76 and 1.49 microM, respectively for DMPP and K). A similar picture emerged with Cd ions, though Cd exhibited an IC50 against K (1.86 microM) slightly lower than the IC50 against DMPP (8.14 microM). 3. Clear cut differences were observed with amiloride, guanethidine, nimodipine and nisoldipine which behaved as selective blockers of DMPP-mediated Ca uptake responses: IC50 values to block DMPP effects were 290, 27, 1.1 and 1.63 microM respectively for amiloride, guanethidine, nimodipine and nisoldipine. Amiloride blocked K-evoked Ca uptake by only 35% and guanethidine did not affect it. Nisoldipine inhibited K-evoked Ca uptake only partially at low concentrations (about 30%); a second blocking component was observed at the highest concentration used (10 microM). At 10 microM, nimodipine blocked K-evoked Ca uptake by 50%. 4. Thus, it seems that the nicotinic receptor mediated Ca uptake pathway can be pharmacologically separated from the K-activated pathway. The results are compatible with the hypothesis that in cultured bovine adrenal chromaffin cells, stimulation of nicotinic receptors recruits a single type of Ca channel which is sensitive to flunarizine, Cd, amiloride, guanethidine, nimodipine and nisoldipine. The results also suggest that K depolarization might be recruiting in addition to this channel, another Ca channel which is highly sensitive to Cd and flunarizine, resistant to nisoldipine, nimodipine and amiloride, and insensitive to guanethidine.