PHARMACOLOGICAL EVIDENCE FOR THE INVOLVEMENT OF Na<sup>+</sup> CHANNELS IN THE RELEASE OF CATECHOLAMINES FROM PERFUSED ADRENAL GLANDS

I Experiments were carried out on perfused adrenal glands of guinea-pig to determine whether veratridine caused the exocytotic release of catecholamine by comparing its effect with that of splanchnic nerve stimulation and secretagogues such as acetylcholine and excess K+.2 Veratridine (100 gM) and excess K+ (56 mM) caused secretion of catecholamine and dopamine-f)-hydroxylase (DBH) activity in the venous effluents in the presence of atropine (30 gM) and hexamethonium (2 mM). Splanchnic nerve stimulation in the presence or absence of physostigmine (100 nM) and infusion of acetylcholine in the presence of physostigmine had the same effect. In all the responses, the release of DBH tended to last for a longer period than that of catecholamine. 3 The ratio of catecholamine to DBH activity appearing in the venous effluents was approximately 9, regardless of the method of stimulation. This value was close to the ratio of catecholamines to the 'soluble' DBH activity found in the chromaffin granules. 4 All the types of stimulation used caused a proportional release of adenine nucleotides and catecholamines in the effluents. The adenine nucleotides were mainly adenosine 5'-phosphate. 5 The ratio of catecholamine to adenine nucleotides was approximately 11, regardless of the method of stimulation. 6 It is suggested that the release of catecholamine induced by veratridine occurs by exocytosis in adrenal glands of guinea-pig.

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“…As already reported (Ito et al, 1978; Diference in the time course of release of catecholamine and dopamine /3-hydroxylate activity…”

Section: Resultssupporting

confidence: 53%

“…Both adrenal glands were perfused and isolated following the general procedure described previously (Ito et al, 1978; Friedman & Kaufman (1965).…”

Section: Methodsmentioning

confidence: 99%

Exocytotic Release of Catecholamine From Perfused Adrenal Gland of Guinea‐pig Induced by Veratridine

Nakazato

Ohga

1980

British J Pharmacology

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“…Table 2). In agreement with previous results (Teraoka et al, 1991) (20 mM (Douglas & Rubin, 1961;Ito et al, 1978;1979;Kilpatrick et al, 1981;Knight & Baker, 1983;Knight & Kesteven, 1983;Wakade & Wakade, 1983). However, the mechanism underlying the depolarization is different between stimulants, ACh and veratridine cause depolarization resulting mainly from the activation of nicotinic receptor channels and voltage-dependent, tetrodotoxin-sensitive Na' channels, respectively.…”

Section: Resultssupporting

confidence: 81%

Inhibitory effects of caffeine on secretagogue‐induced catecholamine secretion from adrenal chromaffin cells of the guinea‐pig

Nakazato

Tani

Sugawara

et al. 1994

British J Pharmacology

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1 The inhibitory action of caffeine on catecholamine secretion induced by secretagogues was investigated in perfused adrenal glands and dispersed chromaffin cells of the guinea-pig. 2 Caffeine (10 mM) caused a reversible inhibition of catecholamine secretion evoked by acetylcholine (ACh, 50 jiM), KCl (56 mM, high K+) and veratridine (100 gtM) and that induced by muscarinic receptor activation in the absence of extracellular Ca2' in perfused adrenal glands.3 In dispersed chromaffin cells, caffeine caused a dose-dependent inhibition of the secretory responses to 100 jiM ACh and veratridine. Forskolin (30 gtM), dibutyryl cyclic AMP (1 mM) and 8-bromo cyclic AMP (1 mM) did not mimic the action of caffeine. 4 In the voltage-clamp, whole-cell recording mode (at a holding potential of -60 mV or -70 mV), ACh (100I1M) evoked an inward current, and depolarizing pulses elicited inward Na+, Ca2" and outward K+ currents. All these responses were partially inhibited by caffeine (20 mM).5 ACh rapidly increased the intracellular concentration of Ca2" ([Ca2+D in fura-2-loaded cells in either the presence or the absence of external Ca2", though its magnitude was decreased by about 50% in Ca2+-free conditions. Caffeine (20 mM) inhibited these ACh-induced increases in [Ca2J]i.6 In permeabilized chromaffin cells, caffeine (20 mM) caused an inhibition of catecholamine secretion evoked by Ca2" (1O pM). 7 These results suggest that caffeine inhibits evoked catecholamine secretion through mechanisms such as the blockade of voltage-dependent Na+ and Ca2+ currents and ACh receptor current, and reduction of the release of intracellularly stored Ca2`and/or Ca2+-sensitivity of the secretory apparatus.

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“…Catecholamine secretion produced by these secretagogues required Ca ions in the incubation medium in which the cells were suspended. The results indicate that isolated adrenal chromaffin cells possess ACh receptors and Na+ channels, activation of which mediates Ca-dependent catecholamine secretion similar to the perfused adrenal glands of guinea-pig (Ito, Nakazato & Ohga, 1978.…”

Section: Resultsmentioning

confidence: 86%

“…Although the release of DBH -is considered to be an index of the exocytotic release of catecholamine from adrenal gland (Viveros et al 1968) and sympathetic neurones (De Potter, De Schaepdryver, Moerman & Smith, 1969), it has been reported that the time course of catecholamine secretion was different from that of concomitant DBH secretion in both tissues (Cubeddu et al 1974; Dixon et al 1975;Jacobs et al 158 S. ITO 1978;Edwards et al 1980;Ito et al 1980;Muscholl et al 1980). It may be possible that delayed output of DBH, compared with catecholamine secretion, results from a delayed washout of DBH from the release site into the circulation because of the presence of diffusion barriers for this large protein.…”

Section: Resultsmentioning

confidence: 99%

Time course of release of catecholamine and other granular contents from perifused adrenal chromaffin cells of guinea‐pig.

Ito¹

1983

The Journal of Physiology

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SUMMARY1. Experiments were carried out to investigate the time course of the release of catecholamine, dopamine-,8-hydroxylase (DBH) and adenine nucleotides from isolated chromaffin cells of guinea-pig adrenal gland.2. When the isolated chromaffin cells were incubated with medium containing acetylcholine (ACh) (0-1 mM), veratridine (0-1 mM) or scorpion (Leiurus quinquestriatus) venom, (10 ,ug/ml.), catecholamine was released into the medium. Catecholamine secretion induced by veratridine or scorpion venom was inhibited by tetrodotoxin (1 gM) but not by atropine (0-1 mM) plus hexamethonium (041 mM). On the other hand, the secretary response to ACh was abolished by the cholinergic blocking drugs but not by tetrodotoxin.3. DBH was released together with catecholamine into the medium in which cells were suspended with these drugs. The ratio of catecholamine (n-mole) to DBH activity (n-mole/hr) appearing in the supernatant was 7-08 + 055, 6-60 + 0X27 and 8X91 + 0 47 for ACh, veratridine and scorpion venom, respectively. These values were close to that found in the lysate of chromaffin granules obtained from guinea-pig adrenal glands (7-37 + 0-39).4. The application of ACh or veratridine to perifused chromaffin cells was found to cause a parallel increase in catecholamine and DBH secretion in the perifusion medium without corresponding amounts of phenylethanolamine-N-methyltransferase leakage. However, DBH secretion tended to last for a longer period than catecholamine secretion.5. Adenine nucleotides were released from perifused chromaffin cells together with catecholamine, by ACh and veratridine. ATP added to the perifusion medium was metabolized to ADP and AMP, of which the ratio (ATP, 21-6 %; ADP, 34 %; AMP, 17-9 %) was close to those of adenine nucleotides released from the cells.6. The secretion ofadenine nucleotides induced by both secretagogues ceased much faster than the catecholamine secretion, so that the molar ratio of catecholamine to adenine nucleotides was gradually increased during and after stimulation. 7. The results indicate that catecholamine secretion is accompanied with a simultaneous release of DBH and ATP from adrenal chromaffin cells. Therefore, it is suggested that the delayed output of DBH, unlike catecholamine secretion, in perfused adrenal glands results from the presence of a diffusion barrier for this protein. The releasable secretary granules of isolated chromaffin cells are suggested to be heterogeneous with respect to the ratio of catecholamine to ATP.

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PHARMACOLOGICAL EVIDENCE FOR THE INVOLVEMENT OF Na⁺ CHANNELS IN THE RELEASE OF CATECHOLAMINES FROM PERFUSED ADRENAL GLANDS

Cited by 31 publications

References 4 publications

Exocytotic Release of Catecholamine From Perfused Adrenal Gland of Guinea‐pig Induced by Veratridine

Exocytotic Release of Catecholamine From Perfused Adrenal Gland of Guinea‐pig Induced by Veratridine

Inhibitory effects of caffeine on secretagogue‐induced catecholamine secretion from adrenal chromaffin cells of the guinea‐pig

Time course of release of catecholamine and other granular contents from perifused adrenal chromaffin cells of guinea‐pig.

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PHARMACOLOGICAL EVIDENCE FOR THE INVOLVEMENT OF Na+ CHANNELS IN THE RELEASE OF CATECHOLAMINES FROM PERFUSED ADRENAL GLANDS

Cited by 31 publications

References 4 publications

Exocytotic Release of Catecholamine From Perfused Adrenal Gland of Guinea‐pig Induced by Veratridine

Exocytotic Release of Catecholamine From Perfused Adrenal Gland of Guinea‐pig Induced by Veratridine

Inhibitory effects of caffeine on secretagogue‐induced catecholamine secretion from adrenal chromaffin cells of the guinea‐pig

Time course of release of catecholamine and other granular contents from perifused adrenal chromaffin cells of guinea‐pig.

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PHARMACOLOGICAL EVIDENCE FOR THE INVOLVEMENT OF Na⁺ CHANNELS IN THE RELEASE OF CATECHOLAMINES FROM PERFUSED ADRENAL GLANDS