Involvement of 3',5'-cyclic adenosine monophosphate in the increase of tyrosine hydroxylase activity elicited by cold exposure

Nicotinic Cholinergic Regulation of Tyrosine Hydroxylase Gene Expression and Catecholamine Synthesis in Isolated Bovine Adrenal Chromaffin Cells

Isolated bovine adrenal chromaffin cells were used to study the nicotinic regulation of tyrosine hydroxylase (TH) gene expression. Continuous exposure of the cells to carbachol or the nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP) produces a time- and concentration-dependent increase in TH enzyme activity, whereas muscarine has no effect. DMPP at 1 microM (EC50 = 0.3 microM) elicits a two- to threefold elevation of both TH activity and TH immunoreactive protein level after 3-5 days in the presence of 2.5 mM calcium; the increase in enzyme levels is significantly less at lower extracellular calcium levels. The rate of hydroxylation of tyrosine to dopamine (DA) in intact cells, an index of endogenous TH activity, increases in parallel with the rise in TH levels. The TH mRNA level is elevated before the increase in protein levels. As determined by nuclear run-on assays, TH gene transcription is stimulated two- to threefold within 30 min of addition of 1 microM DMPP to the cells; transcription returns to basal levels by 2 h. Nitrendipine (20 microM) blocks the stimulation of transcription by DMPP. Pretreatment of the cells with cycloheximide (5 microM) does not prevent the DMPP stimulation of transcription. Forskolin (10 microM) also increases TH transcription (fourfold in 15 min) by a mechanism that is not blocked by cycloheximide. These results show that nicotinic receptor stimulation increases TH mRNA synthesis, TH protein levels, and TH activity in a calcium-dependent manner. Furthermore, the nicotinic influence on TH gene expression does not appear to require the synthesis of a protein factor for its effects. That in situ DA synthesis rates are elevated consequent to the rise in TH levels demonstrates that TH induction serves as a mechanism for enhancing the catecholamine-synthesizing capacity of the chromaffin cell on a long-term basis.

Nicotine-induced regulation of tyrosine hydroxylase activity in adrenal gland of transgenic mouse carrying human tyrosine hydroxylase gene

We investigated the effect of subcutaneous injection of nicotine on in vitro tyrosine hydroxylase (TH) activity in adrenal gland and brain of the transgenic mice carrying an 11-kb fragment containing the entire human TH gene. Injection of 5 mg nicotine/kg (as free base) for 3 days caused a statistically significant increase in vitro TH activity in the adrenal gland, whereas brain TH activity was not affected at all. The adrenal gland of non-transgenic C57BL/6J mice treated in the same way as for transgenic mice tended to enhance TH activity, although not to a significant level. This observation might indicate the possibility that the machinery used by nicotine in regulating the properties or expression of TH in the adrenal gland should be similar between transgenic and non-transgenic mice.

Epinephrine-induced decrease in repetitive extrasystole threshold is reversed by tyrosine in conscious dogs

Previous studies indicate that availability of L-tyrosine, the precursor for catecholaminergic neurotransmitters, reduced psychological and physiological effects of stressful situations including hypotension, cold and behavioral stress. The current study examined the effect of L-tyrosine administration on cardiac vulnerability to arrhythmia induced by an infusion of epinephrine in conscious dogs. Heart rate, mean arterial pressure and cardiac electrophysiologic parameters, i.e., effective refractory period and repetitive extrasystole threshold, were measured during infusion of epinephrine (0.3 micrograms/kg/min x 30 min), before and after L-tyrosine (B mg/kg iv bolus). Epinephrine administration significantly increased heart rate by 39% (p less than 0.05), and decreased repetitive extrasystole threshold by 33% (p less than 0.05). Mean arterial pressure and effective refractory period were unchanged. Following L-tyrosine, repetitive extrasystole threshold was restored to baseline levels. Tyrosine may thus ameliorate stress-induced increases in ventricular vulnerability to arrhythmias in conscious animals.

Effect of carbachol and 56 mm-potassium chloride on the cyclic AMP-mediated induction of tyrosine hydroxylase in neuroblastoma cells in culture

Tyrosine hydroxylase (TH) activity is increased two- to threefold in neuroblastoma cell line NBP2 maintained in culture for 48 h in the presence of either the inhibitor of cyclic AMP-phosphodiesterase (PDE), 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (RO 20-1724), or the activator of adenylate cyclase, prostaglandin E1 (PGE1). Cyclic AMP levels are elevated 70-80% and 30-40% throughout the 48-h treatment with RO 20-1724 and PGE1, respectively. Carbachol does not affect either basal TH activity or cyclic AMP levels in the cells. However, the cholinergic agonist delays the induction of TH elicited by either RO 20-1724 or PGE1. This delay is prevented by atropine. The elevation in cyclic AMP levels elicited by either RO 20-1724 or PGE1 is blocked for 1 h or 15 min, respectively, after treatment with carbachol. Cyclic AMP levels then begin to rise until they reach those levels observed in the presence of RO 20-1724 or PGE1 alone by 12 h or 1 h of treatment, respectively. Time course studies demonstrate that this transient inhibition of the elevation of cyclic AMP is associated with a 48-h delay in the induction of TH elicited by either RO 20-1724 or PGE1. In contrast, the induction elicited by 8-bromo cyclic AMP is unaffected by carbachol. A depolarizing concentration (56 mM) of KCl produces a 24-h delay in the induction of TH elicited by RO 20-1724, without affecting the concomitant elevation of cyclic AMP produced by the PDE inhibitor. Furthermore, 56 mM-KCl inhibits the induction of TH elicited by 8-bromo cyclic AMP. It thus appears that carbachol delays the induction of TH by transiently inhibiting the elevation of cyclic AMP, whereas potassium depolarization delays the induction of TH by inhibiting a process with a site of action that is distal to the elevation of cyclic AMP.

Effects of db cAMP on tyrosine hydroxylase activity of ganglia and nerve endings

Preincubation of intact superior cervical ganglia or nictitating membrane for 2 h with dibutyryl cyclic AMP (db cAMP) increased the hydroxylation of tyrosine. This effect was not blocked by the protein synthesis inhibitor, cycloheximide. The Km of tyrosine hydroxylase for the substrate, tyrosine, and for the cofactor, reduced pteridine, were decreased by db cAMP. There were no changes in the Vmax of the enzyme. The inhibitory potency of noradrenaline on the hydroxylation of tyrosine was also decreased. Thus an inductive effect may be ruled out. The activation of the enzyme was only observed when the tissues were preincubated with the db cAMP and not when the cyclic nucleotide was added to the isolated enzyme. Preincubation of cervical ganglia for 4 h with db cAMP increased activity of decarboxylase and monoamine oxidase in tissue homogenates without changing the tyrosine hydroxylase activity.

Acetylcholine and cAMP in adrenal medulla:indirect effect

Catecholamine release and cAMP accumulation were studied in bovine adrenal medulla slices in vitro. Acetylcholine (10(-4) M) and salbutamol (10(-6) M) caused increased release of catecholamines and accumulation of cAMP. Incubation in Ca2+ -free medium abolished the release of catecholamines and the increase of cAMP caused by acetylcholine but not that caused by salbutamol. In a membrane fraction of adrenal medulla acetylcholine (10(-4) M) had no effect on adenylate cyclase activity but salbutamol (10(-6) M) caused substantial activation of adenylate cyclase. It is suggested that acetylcholine has no direct effect on adenylate cyclase or cAMP in adrenal medulla and the accumulation of cAMP observed in slices incubated with acetylcholine is due to the effect of catecholamines, released by acetylcholine, on the medullary cells.

Histamine, cyclic AMP, and gastric secretion in the dog

Canine gastric mucosal cyclic AMP content was determined at 1, 5, 30, 60, and 120 min after commencing a 2-hr continuous intravenous infusion of histamine of sufficient dose to elicit a brisk acid secretory response from the dog stomach. The increase in acid output was significant at 30 min and stabilized at the stimulated level for the duration of histamine infusion. By contrast, there was no significant increase in mucosal cyclic AMP content at any time of measurement. Our findings indicate that the acid secretory response of the canine stomach to histamine does not require prior accumulation of cyclic AMP in the mucosal tissue.

Evolution in vivo of the synthesis rate of catecholamines in various peripheral organs of the rat during cold exposure

The synthesis of catecholamines (CA) has been studied in the heart, spleen, submaxillary glands and adrenals of rats exposed to 4 degrees C for 2.5, 24 or 48 h. The synthesis rate has been estimated 30 min after an i.v. injection of 3H tyrosine (TY) by the evaluation of the ratio: 3H-CA specific activity/3H-TY specific activity. In the sub-maxillary glands, cold exposure reduced the noradrenaline (NA) synthesis by 40% at times 24 and 48 h. In the spleen, NA synthesis was multiplied by a factor 1.6 at times 2.5 and 24 h and 2.8 at time 48 h. In the heart, it was increased by a factor 1.3 after 2.5 h, 2.8 after 24 h and 5.5 after 48 h: an important fall in cardiac NA level was observed during the first 24 h of cold exposure indicating that the synthesis capability was unsufficient to compensate the cold-induced NA release. In the adrenals, adrenaline + NA synthesis was not significantly enhanced during the first 24 h of cold exposure and increased by a factor 2.4 at time 48 h. The important increases in CA synthesis which are observed during the 24-48 h interval are likely consecutive to the induction of tyrosine hydroxylase which has been reported in the rat exposed to cold.

Association between the increase of cAMP content and the trans-synaptic induction of tyrosine hydroxylase in rat adrenal medulla. Studies with dexamethasone and reserpine

When dexamethasone 0.25 or 2.5 mumole/kg i.p. was injected 2 h before reserpine (16 mumol/kg i.p.) the time course of the increase in cAMP content of rat adrenal medulla was changed. Reserpine alone caused a monophasic increase lasting between 1-2 h; reserpine after dexamethasone caused a biphasic increase: the immediate response, lasting between 15 and 30 min, was followed by a secondary increase beginning 2-3 h after reserpine and lasting for several hours. The overall increase in cAMP content elicited by reserpine during the 8 h following injection remained unchanged or was even increased, depending on the dose of dexamethasone. Pretreatment with dexamethasone, which delayed the increase in cAMP, also delayed the activation and translocation of protein kinase and the induction of tyrosine hydroxylase caused by reserpine in adrenal medulla. The action of reserpine on the cAMP content of adrenal medulla required an intact innervation and did not appear to be related to increased secretion of ACTH from pituitary. In denervated adrenals reserpine failed to increase the cAMP content of the medulla but not that of the cortex.

Effect of recurrent stress on postnatal increase of tyrosine hydroxylase

Tyrosine hydroxylase is present at birth and reaches adult levels in the hypothalamus usually during the second month. Recurrent stimulation of intrahypothalamic noradrenergic structures shortened this period of maturation in a statistically significant manner.

Cyclic AMP, cyclic GMP, and glucocorticoids as potential metabolic regulators of epidermal proliferation and differentiation

The two cyclic nucleotides, cyclic AMP and cyclic GMP, appear to be central to the metabolic regulation of cell proliferation and differentiation in various cells. Moreover, in many systems glucocorticoids appear to act in concert with or parallel to cyclic AMP. The available evidence suggests that these three molecular species--cyclic AMP, cyclic GMP, and glucocorticoids--may be essential to the normal regulation of epidermal proliferation and differentiation. In 1970, we suggested that perturbed epidermal homeostasis, exemplified by psoriasis, might be associated with low cellular levels of cyclic AMP and, in 1972, with high levels of cyclic GMP as well. Subsequent measurements of these two cyclic nucleotides in our laboratory showed a probable reduction in the cyclic AMP/cyclic GMP ratio in lesional psoriatic tissue. This led to the hypothesis that the cardinal features of psoriatic epidermis--glycogen accumulation, excessive proliferation, and reduced cell specialization--are the results of this reduced ratio. A corollary of this hypothesis was that a psoriatic lesion could not begin or exist without this altered cyclic nucleotide ratio. Recently, four different agents--lithium, a beta adrenergic blocking agent, antimalarials, and iodide--have been found to exacerbate psoriasis and to reduce the formation of cyclic AMP in various tissues. Consequently we believe that cyclic nucleotides are of central importance in the pathogenesis of the epidermal component of psoriasis.

The effect of hydrocortisone and adrenocorticotrophic hormone on monoamine oxidase and tyrosine hydroxylase in explant cultures of embryonic chick sympathetic ganglia

Sympathetic ganglia from 13- to 15-day-old embryonic chicks were cultured for up to 2 days in Leighton tubes. The influence of hydrocortisone and ACTH added to the culture medium on the enzymes monoamine oxidase (MAO) and tyrosine hydroxylase was studied. Hydrocortisone (5 times 10(-5)M) had no effect on tyrosine hydroxylase but increased MAO activity by up to 46 percent over control values under conditions of low or zero nerve growth factor (NGF) concentration. ACTH also increased ganglionic MAO activity, the effect again depending on NGF concentration. This time the maximal response (an increase of 50 percent over controls) was seen at high NGF concentrations. This response was similar to the effect of 1 mM dibutyryl cyclic AMP, and was blocked by 1 times 10-5 M propranolol and 10 muM prostaglandin E(1). ACTH only slightly increased tyrosine hydroxylase activity and this effect was due to a small (18 percent) increase in sympathetic neurone number. Guanosine 5-diphosphate (0.5 mM) was found to increase tyrosine hydroxylase activity by 57 percent and this effect was blocked by the presence of ACTH.

The adrenal medulla: a model for studies of hormonal and neuronal storage and release mechanisms

We have observed that phospholipids and protein of the catecholamine (CA) storage granules, i.e. the chromaffin granules, interact in an in vitro system to form liposomal particles, which in many respects resemble the intact matrix of the bovine chromaffin granule. A model has been suggested which consists of an aqueous phase, containing the acidic chromogranins and intact dopamine-beta-hydroxylase (DBH) ATP and CA, embedded in a liquid crystal of the matrix phospholipids. Ca2+ may play a significant role in the sequence of functional transitions of such an organelle, not only in the accumulation of Ca2+, as during the secretory phase of the intact cell, but also as the agent inducing a separation of the outer membrane bilayer from the matrix phase to be released, as during exocytosis. Furthermore, a liposome model of the matrix may also tentatively explain the occurrence of intact matrices in the interstitium of stimulated glands. Recent evidence for the identity between chromogranin A and DBH subunits have been summarized and a possible role for the inactive subunits in the ionic binding of ATP and CA in the aqueous phase of the matrix is discussed. A role of Ca2+ and cyclic AMP in the mediation of beta-adrenergic modulation is postulated on the basis of our recent work on acetylcholine-induced release of CA from perfused and stimulated bovine adrenals. We conclude that such a beta-adrenergic modulation is secondary to that of the cholinergic response. Hence, this activation is able to enhance the output induced by mild cholinergic stimulation although insufficient to evoke a CA release by itself.

Ornithine decarboxylase activity: control by cyclic nucleotides

Both exposure to cold and administration of aminophylline result in rapid increases in cyclic adenosine monophosphate (cyclic AMP) in the adrenal medulla and adrenal cortex. These increases are followed by dramatic increases in ornithine decarboxylase activity is due to new enzyme systhesis. The data suggest that the decarboxylase activity is regulated by an increase in cyclic AMP.

Effect of hypophysectomy on cAMP changes in rat adrenal medulla evoked by catecholamines and carbamylcholine

It was the aim of this study to investigate the mechanisms responsible for changes in 3',5'-cyclic adenosine monophosphate (cAMP) in the rat adrenal medulla occuring after administration of carbamylcholine, histamine, ACTH and various phenylethylamines. Carbamylcholine, ACTH, histamine, noradrenaline and dopamine produced marked (500-900%) increases in adrenal cAMP which were very similar in both adrenal cortex and medulla both with respect to time-course and relative extent. Interestingly isoprenaline and adrenaline did not influence cAMP levels even at excessively high doses. In all cases studied transsection of the splanchnic fibers supplying the adrenals reduced the increase in medullary cAMP by not more than 25--30%, suggesting that cAMP levels in the adrenal medulla are predominantly regulated by non-neuronal mechanisms. This assumption was strongly supported by the observation that hypophysectomy completely abolished the 500--600% increase in cAMP produced by 50 mumol/kg of dopamine and reduced the 700% increase resulting from 4.4 mumol/kg of carbamylcholine to 70%. In spite of the marked increase in cAMP produced by single and repeated doses of dopamine in the adrenal medulla there was no subsequent induction of tyrosine hydroxylase (TH). Moreover carbamylcholine (8.2 mumol/kg) evoked TH induction only in innervated adrenals whereas after denervation, in spite of the large (+ 500%) and prolonged (more than 90 min) increase in cAMP, no TH induction could be observed. It is concluded that adrenal medullary cAMP is predominantly regulated by the pituitary gland via the adrenal cortex and only to a much smaller extent--if at all--by direct cholinergic mechanisms, which are responsible for the initiation of TH induction.

Biosynthesis of tyrosine hydroxylase in rat adrenal medulla after exposure to cold

Exposure of rats to cold increases the content of tyrosine hydroxylase [EC 1.14.16.2; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating)] in adrenal medulla, causing a long-lasting enhancement of the enzymatic activity. We have used an antibody specific to tyrosine hydroxylase to study the molecular mechanisms involved in the trans-synaptic induction of adrenal tyrosine hydroxylase. The rate of [(3)H]-leucine incorporation into adrenal tyrosine hydroxylase was measured by specific immunoprecipitation at various times after exposure to cold (4 hr). This enhanced rate of incorporation was evident between 11 and 30 hr after the beginning of exposure to cold, but not at 7 and 50 hr. The increase of (3)H incorporation preceded the maximal enhancement of adrenal tyrosine hydroxylase activity, which occurred about 30 hr after stimulation. Neither the activity of tyrosine hydroxylase nor the rate of (3)H incorporation into tyrosine hydroxylase in cervical sympathetic ganglia was changed by 4 hr of exposure to cold. The rate of degradation of tyrosine hydroxylase was estimated at 26 and 50 hr after the beginning of cold stress, as determined by the technique of double-isotope labeling. The data indicate that the tyrosine hydroxylase degradation rate was not reduced by exposure to cold. Thus, the induction of adrenal tyrosine hydroxylase appears to be due to an increased rate of its synthesis.

The long-term regulation of tyrosine hydroxylase activity in cultured sympathetic ganglia: role of ganglionic noradrenaline content

1 An organ culture system is described for the in vitro maintenance of superior cervical sympathetic ganglia taken from mice of any age. The relation of tyrosine hydroxylase (T-OH) activity to ganglionic noradrenaline (NA) content has been investigated under various culture conditions.2 Depolarizing stimuli such as raised extracellular potassium and ouabain evoked increases of approximately 70% in the T-OH activity of cultured ganglia over a 48 h period. Exposure to a high concentration of potassium (high K(+)) for 30 min at the start of a 48 h culture was sufficient to elicit significant increases in T-OH activity.3 Depolarization-induced rises in T-OH activity were observed after culture in the presence or absence of nerve growth factor.4 The NA content of ganglia, cultured for 48 h in the presence of high K(+), ouabain, reserpine, clorgyline and alpha-methyl-p-tyrosine, showed no constant relation to their T-OH activity.5 Dibutyryl cyclic adenosine 3'-5'-monophosphate (dibutyryl cyclic AMP) mimicked high K(+) in its effect on ganglionic T-OH activity and NA content. Theophylline enhanced the potassium effects.6 Rises in the T-OH activity of ganglia cultured in the presence of high K(+) and dibutyryl cyclic AMP were abolished if the protein synthesis inhibitors cycloheximide or actinomycin D were present in the culture medium.7 It is concluded that the link between prolonged depolarization and rises in T-OH activity does not seem to depend upon changes in ganglionic NA content. In the intact animals, trans-synaptic modulation may take the form of a depolarization-induced rise in the cyclic AMP content of sympathetic ganglionic neurones leading to nuclear mediated synthesis of T-OH.

Location of an isoproterenol-responsive cyclic AMP pool in adrenergic nerve cell bodies and its relationship to tyrosine 3-monooxygenase induction

To decide whether adenosine 3':5'-cyclic monophosphate (cyclic AMP) plays a role as a second messenger in the trans-synaptic induction of tyrosine 3-monooxygenase (EC 1.14.16.2), it is desirable to discriminate between neuronal and extraneuronal changes in cyclic AMP concentration. Treatment of newborn rats with nerve growth factor antiserum or 6-hydroxydopamine, leading to destruction of 61-85% of the adrenergic nerve cell bodies in the superior cervical ganglion, led to a decrease in cyclic AMP of only 16-28%. This observation demonstrates that a relatively small portion of cyclic AMP is localized in the adrenergic neurons. However, administration of isoproterenol produced an increase (12-fold) in cyclic AMP only in this neuronal pool. Neither single nor repeated injections of isoproterenol led to induction of tyrosine monoxygenase. This, together with previous observations that experimental conditions leading to induction of the enzyme do not produce significant increases of cyclic AMP in the whole ganglion, is taken as an indication that cyclic AMP is not acting as a second messenger in the trans-synaptic induction of tyrosine monooxygenase in the rat superior cervical ganglion. In the rat adrenal medulla, treatment with reserpine led to both a shortlasting (60-90 min) increase in cyclic AMP and a subsequent induction of tyrosine monooxygenase. However, the increase in cyclic AMP was almost completely prevented (40 compared to 320%) by pretreatment of the rats with propranolol while the induction of tyrosine monooxygenase was not diminished. This observation also argues against an exclusive key-function of cyclic AMP in trans-synaptic induction of tyrosine monooxygenase in the adrenal medulla.

Cyclic adenosine monophosphate: selective increase in caudate nucleus after administration of L-dopa

Treatment with the dopamine precursor L-dopa produced a significant accumulation of adenosine 3',5'-monophosphate (cyclic AMP) in the caudate nucleus of the rat. In contrast, there was no change in the amount of cyclic AMP in the cerebellum. Accumulation of cyclic AMP in the caudate nucleus after administration of L-dopa was prevented by prior treatment with the decarboxylase inhibitor RO 4-4602. These observations and those in other laboratories support the assumption that dopamine formed from L-dopa selectively activates striatal adenylate cyclase. The in vivo activation of adenylate cyclase after treatment with L-dopa may be a useful model for studying neurological and psychiatric disorders that are thought to involve the dopaminergic system of the brain.