Ionomycin stimulates secretion of catecholamines from cat adrenal gland and spleen

Ionomycin, a polyether antibiotic, stimulated the secretion of catecholamines and dopamine beta-hydroxylase from perfused adrenal glands and [3H]norepinephrine ([3H]NE) from spleens of the cat. Release was calcium dependent, and strontium or barium did not substitute for calcium. Ionomycin failed to release [3H]NE from reserpinized spleens. High magnesium did not interfere in the ionomycin response, but lanthanum and manganese blocked it. Ionomycin response that was pH dependent was not affected by potassium depolarization. The secretory response to ionomycin was enhanced when both glycolysis and oxidative metabolism were inhibited. It is concluded that ionomycin introduces calcium into the chromaffin cells and adrenergic nerve terminals to cause the secretory response and that a rise in intracellular calcium may be an adequate stimulus for secretion.

Adrenergic nerve-blocking activity of a new guanidine derivative

The effects of 4-7-exo-methylene-hexahydroisoindoline-ethyl guanidine hemisulfate (no. 865-123) on norepinephrine release were investigated in the perfused spleen on the cat. No. 865-123 irreversibly blocked the release of norepinephrine evoked by nerve stimulation. Tetraethylammonium, 4-amino-pyridine and guanidine readily reversed this inhibitory effect, and the norepinephrine output was nearly tripled after repeated stimulation of the nerves. On subsequent perfusion with Krebs' solution without any drugs, the inhibitory effect of no. 865-123 partially reappeared. Perfusion pressure responses followed the same pattern as release except during the final perfusion period with Krebs' solution. It is suggested that tetraethylammonium, 4-aminopyridine and guanidine allow greater than normal amounts of calcium to accumulate inside the adrenergic nerve terminals during an action potential to reverse no. 865-123 blockade of norepinephrine release.

Potentiation of K+-evoked catecholamine release in the cat adrenal gland treated with ouabain

1 A vigorous catecholamine secretory response was evoked by small increments (2-10 mM) of the extracellular concentration of K+ ([K+])o) in cat adrenal glands treated with ouabain (10(-4) M), and perfused with Krebs-bicarbonate solution at room temperature. 2 The secretory response depends on [K+]o; increments of [K+]o as small as 2 mM for 2 min evoked a clear secretory response; at 10-17.7 mM K+, the maximal secretory response was observed. In normal glands, not treated with ouabain, no increase of the rate of catecholamine output was observed by raising [K+]o up to 17.7 mM for 2 min. 3 The K+ secretory response was time-dependent, requiring at least 1 min to be initiated; on continued exposure to 10 mM [K+]o, the enhanced response remained for at least 1 h. 4 In low [Na+]o, the K+-secretory response was unchanged. However, in 0-Ca2+, high-Mg2+ solutions, or in the presence of D600, an organic Ca2+ antagonist, it was abolished. 5 The K+-induced secretory response was not altered in the presence of tetrodoxin or tetraethylammonium. 6 It is concluded that ouabain potentiated the catecholamine secretory response to raised [K+]o by increasing the amount of Ca2+ available to the secretory machinery through (a) mobilization of an enhanced pool of membrane-bound Ca2+, (b) activation of membrane Ca2+ inward current; or (c) decrease of intracellular Ca2+ buffering systems. The activation by ouabain of a membrane Na+-Ca2+ exchange system is not involved in this K+-secretory response. It is suggested that the plasma membrane ATPase enzyme system, by changing the affinity of its Ca2+ binding sites, might control the availability of this cation to the secretory machinery and, therefore, modulate catecholamine secretion in the adrenal gland.

Correlation between catecholamine release and sodium pump inhibition in the perfused adrenal gland of the cat

1 Ca(2+) reintroduction to retrogradely perfused and ouabain (10(-4) M)-treated cat adrenal glands caused a catecholamine secretory response which was greater the longer the time of exposure to the cardiac glycoside. Such a response was proportional to the external Na(+) concentration [Na(+)](o).2 A qualitatively similar, yet smaller response was observed when glands were perfused with Krebs solution lacking K(+) ions; thus, K(+) deprivation mimicked the secretory effects of ouabain. Catecholamine secretion evoked by Ca(2+) reintroduction in K(+)-free solution (0-K(+)) was also proportional to [Na(+)](o) and greater the longer the time of exposure of the gland to 0-K(+) solution.3 The ionophore X537A also mimicked the ouabain effects, since Ca(2+) reintroduction to glands treated with this agent (25 muM) caused a sharp secretory response. When added together with X537A, ouabain (10(-4) M) did not modify the response to the ionophore.4 N-ethylmaleimide (NEM), another Na(+), K(+)-ATPase inhibitor, did not evoke the release of catecholamines; on the contrary, NEM (10(-4) M) inhibited the catecholamine secretory response to high [K(+)](o), acetylcholine, Ca(2+) reintroduction and ouabain.5 Ouabain (10(-4) M) inhibited the uptake of (86)Rb into adreno-medullary tissue by 60%. Maximal inhibition had already occurred 2 min after adding the drug, indicating a lack of temporal correlation between ATPase inhibition and the ouabain secretory response, which took longer (about 30-40 min) to reach its peak. NEM (10(-4) M) blocked (86)Rb uptake in a similar manner.6 The results are further evidence in favour of the presence of a Na(+)-Ca(2+) exchange system in the chromaffin cell membrane, probably involved in the control of [Ca(2+)](i) and in the modulation of catecholamine secretion. This system is activated by increasing [Na(+)](i), either directly (ionophore X537A, increased [Na(+)](o)) or indirectly (Na(+) pump inhibition). However, the simple inhibition of Na(+) pumping does not always lead to a catecholamine secretory response; such is the case for NEM.

[Infections causes of congenital abnormalities]

Revisão sumária das causas infecciosas das anomalias congênitas englobando as malformações, que correspondem a estruturas anormais orgânicas ou tissulares decorrentes de erros primários de morfogenese embrionaria e deformações, que se instalam no período fetal da vida intrauterina, correspondentes a alterações de forma e estrutura de órgãos primitivamente bem constituidos.

Contractile effect of vanadate and other vanadium compounds on the rat vas deferens

Sodium metavanadate (NaVO3), vanadium pentoxide (V2O5) and vanadyl sulphate (VOSO4), evoked rhythmic and tonic contractions of the normal and reserpinized rat isolated vas deferens. Contractions were not observed by the use of vanadium trichloride (VCl3) The order of potency of these compounds, for their maximum contractile effects was NaVO3 greater than V2O5 greater than VOSO4 greater than VCl3. Differences in pD2 values were less than 0.5 long units in relation to the first compound. Vanadium-induced contractions were blocked by Ca2+ deprivation, nifedipine, Mg2+, Mn2+, Ni2+ and Co2+, indicating the involvement of a loosely bound or extracellular calcium-dependent mechanism. It is still unclear whether this calcium translocation was related, or not, to changes in Na+, K+-ATPase activity. Since ouabain blocked the action of vanadyl or vanadate non-competitively, it is concluded that vanadium compounds and ouabain induce their effects by interacting with different sites in vas deferens, both of which may or may not be located on the (Na+, K+)ATPase enzyme complex.

Tracheoesophageal fistula and anomalies of thoracic vessels: their occurrence in a case of congenital rubella

Virologic, gross, and microscopic studies of rubella embryopathy were performed. The presence of esophageal atresia with tracheal fistula allied with anomalies of the thoracic vessels were seen. We believe that both the mechanical action of the anomalous vessels on the developing organ, and the vascular degenerative aortic lesions, which are identical to those described in rubella syndrome, are probable causes of the esophageal malformation.

Intrauterine infection with mumps virus

The histopathologic study of 3 cases of gestational mumps is presented. The tissue studies was obtained from a spontaneous abortion (case 1) and from 2 therapeutic abortions (cases 2 and 3). Severe placental and fetal lesions were observed, indicating a probable association with maternal mumps. The main placental lesion was a diffuse proliferative necrotic villitis with severe lesions in the fetal vascular circuit, probably the cause of death. In the fetal viscera, areas of necrosis and mineralization were observed. Viral inclusions identical to those described in mumps infection were observed in the chorionic and fetal tissues.

The effects of the calcium ionophore, A23187, on the axoplasmic transport of dopamine beta-hydroxylase

1 The effects of the ionophore, A23187, on the intra-axonal transport of dopamine beta-hydroxylase (DBH) were investigated in the cat hypogastric nerve-inferior mesenteric ganglion preparation by monitoring, in vitro, the enzyme accumulation above a ligature, 2 to 2.5 cm distal to the ganglion. 2 DBH accumulation in the proximal segment immediately above the ligature (P1) increased linearly up to 6 h, during incubation in normal Krebs solution at 37 degrees C. The ionophore, A23187, interfered with the enzyme accumulation, but did not modify the previously accumulated DBH activity present in P1. 3 The blocking effects of A23187 on DBH transport were greatly impaired in the absence of extracellular calcium ions; an excess of calcium in the bathing solution (7.5 mM) itself blocked the enzyme transport by 50%. 4 A23187 did not significantly modify the levels of adenosine triphosphate (ATP) in the segments P1 and P2 of the nerve proximal to the ligature. 5 Nerves incubated in an A23187-containing medium showed many mitochondria of normal shape and fine structure; however, typical microtubules or filaments were not seen in these preparations. 6 The results suggest that the ionophore A23187, by considerably raising the axoplasmic ionized calcium levels, interferes with the assembling of microtubules. In this manner, the ionophore would inhibit the transport of adrenergic vesicles and therefore of DBH along the axon. The results also provide additional evidence in favour of the view that for the transport system to work adequately, it is necessary to maintain the intra-axoplasmic ionized calcium concentration between certain critical levels.

Action of nicotine on sympathetic nerve terminals

Interaction between 4-aminophrydine (4-AP) and nicotine on sympathetic nerve terminals was studied in the isolated cat spleen slices, labeled with [3H]norepinephrine ([3H]NE). Incubation of slices for 5 min at 37 degrees C in low (50 microM) and high (2 mM) concentrations of nicotine released 0.8 +/- 0.08 and 2.73 +/- 0.39% of tissue [3H]NE. Tetrodotoxin (TTX) blocked the response to low nicotine but not to high nicotine. Low nicotine did not release [3H]NE in the absence of calcium. Response to high nicotine which persisted in calcium-free solution was blocked by ethylene glycol bis(beta-aminoethyl ether)N,N'-tetra-acetic acid. 4-AP (1 mM) not only enhanced the response to low nicotine but it effectively antagonized the suppressant effects of TTX and calcium-free solution on release induced by low nitotine. Restoration of release by 4-AP from TTX-blocked preparations occurred in the absence of calcium in the perfusion medium, but lanthanum (1 mM) blocked it. Restoration of release from spleen slices incubated in calcium-free Krebs' solution by 4-AP was blocked by lanthanum and prolonged incubation in calcium-free ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraaectic acid solution. It is concluded that at lower doses nicotine, by acting on nicotinic receptors, depolarizes the sympathetic nerve terminals to set off propagated action potentials which are responsible for NE release, and that 4-AP restores nicotine response in the presence of TTX or in the absence of calcium by mobilizing calcium both from extracellular and intracellular sources.

On the release of catecholamines and dopamine-beta-hydroxylase evoked by ouabain in the perfused cat adrenal gland

1 Secretion of catecholamines (CA) and dopamine-beta-hydroxylase (DBH) activity from the retrogradely perfused cat adrenal gland was studied following ouabain infusion. Perfusion with ouabain (10(-4) M) for 10 min caused a gradual release of CA in the effluent which reached its peak 30 min after the ouabain pulse, and was maintained constant for at least 1 h. The effect of ouabain seemed to be irreversible. 2 Mecamylamine, while blocking the CA secretory effects of acetylcholine (ACh) perfusion, did not affect the secretion of CA evoked by ouabain. In denervated adrenal glands, ouabain-induced CA secretion was similar to that in the contralateral, innervated gland. However, physostigmine perfusion potentiated the CA secretory effects of ouabain. 3 The release of CA evoked by ouabain was accompanied by a proportional release of DBH activity. The time course of appearance of DBH activity followed the pattern of CA release. 4 The CA and DBH outputs in response to a pulse of ouabain were suppressed in the absence of calcium. Calcium reintroduction to a calcium-free perfused, ouabain-treated gland not only restored but greatly potentiated the release of CA and DBH. The amplitude of the secretory response to calcium reintroduction in ouabain-treated glands was proportional to the extracellular calcium concentration, and was antagonized by an external sodium-deficient medium. 5 These data demonstrate that ouabain releases CA from the perfused cat adrenal gland by a calcium-dependent exocytotic mechanism. The secretory effect of ouabain is not secondary to the release of ACh from cholinergic nerve terminals present in the adrenal gland, but due to a direct action on the chromaffin cell itself. In addition, the results suggest that this action is exerted through redistribution of monovalent cations secondary to the inhibition by the glycoside of the sodium pump. Such monovalent cation redistribution may cause a rise of intracellular ionized calcium levels through the activation of an internal sodium-dependent calcium influx system probably located in the chromaffin cell membrane.

Release of noradrenaline from cat spleen slices by potassium

1 When cat spleen slices were exposed to a potassium-enriched (140 mM) Krebs solution, 367 +/- 31 ng g-1 5 min-1 of noradrenaline (NA) was released into the bathing medium. 2 Phenylephrine and clonidine (10(-7) to 10(-3) M) did not significantly modify the potassium-evoked NA release; acetylcholine decreased it in a dose-dependent manner. 3 Phenoxybenzamine increased NA release by 50% but phentolamine did not alter it; high concentrations of this drug greatly decreased NA release. Cocaine increased the NA release by about 30%. 4 It is suggested that the failure of sympathomimetic amines to depress, and of alpha-adrenoceptor blocking agents to enhance the release of NA by high potassium concentrations may be related to prolonged depolarization of the nerve terminals, which may desensitize presynaptic alpha-receptors. The fact that the same drugs are able to modify NA release during electrical nerve stimulation may be ascribed to the much shorter periods of depolarization occurring under these conditions.

Amnion nodosum and congenital ichthyosis

Histologic characteristics of the placentas in four cases of amnion nodosum and congenital ichthyosis, a rare association, are presented. Two cases were missed abortions of a single multiparous woman, supporting the hypothesis that in congenital ichthyosis amnion and skin share an abnormal genetic trait. As the amnion showed no hyperkeratosis, it is likely that the amniotic lesions are related to an increased deposition of keratotic plugs on the amnion. Oligohydramnios was verified in two cases; urinary tract malformations were absent in all. The histologic characteristics of the placentas were similar. Noteworthy was the aspect of the chorionic vessels, whose lumens were reduced or obliterated. Perhaps this feature contributed to the poor nutrition of the amnion, a fact assumed by some authors to explain lesions of amnion nodosum. As these vascular alterations are common after fetal death, it is only in the placenta of the newborn that the vascular changes, compatible with rubella vasculitis, may have altered the nutrition of the amnion.

Depletion and recovery of catecholamines in the rat adrenal medulla and its relationship with dopamine beta-hydroxylase

Exposure of rats to a stressing atmosphere containing 20% CO 2 for 5 h did not affect the level of adrenal catecholamines (CA) or dopamine β-hydroxylase (DBH) activity. Rats given reserpine showed a 40% decrease in adrenal CA in 5 h and a 90% decrease in 24 h, whereas rats given reserpine and then exposed to CO 2 for 5 h showed a decrease of 95% in adrenal CA at the end of the 5 h exposure as well as at 24 h. DBH activity was not altered either at 5 or 24 h after treatment with reserpine or reserpine plus CO 2 . Pretreatment with mecamylamine prior to the combined treatment with reserpine plus CO 2 prevented the maximum depleting effect of such treatment on adrenal CA. Following combined treatment with reser­pine plus CO 2 in unilaterally splanchnicotomized rats, levels of CA were unchanged in the adrenal gland with the nerve supply interrupted, while the content of CA in the right contralateral innervated gland was maximally depressed. Exposure of rats to CO 2 for 5 h immediately or 24 h after reserpine resulted in an additional lowering of adrenal CA when compared to the levels of CA in rats treated with reserpine alone. However, exposure to CO 2 48 h or more after reserpine injection resulted in no additional lowering of CA. The pattern of recovery of rat adrenal CA following depletion with reserpine plus CO 2 showed that levels of CA remained depressed from 5 to 48 h, followed by a modest recovery at 72 h and essentially complete recovery in about 6 days. In contrast, the recovery pattern following depletion with reserpine alone showed that levels of CA recovered to about half of normal 48 h and were essentially normal in 4–5 days. After treatment with reserpine alone, DBH activity was unchanged from the control level up to 1 day but it increased on the second day and remained high for 4–5 days, After reserpine + CO 2 , DBH activity was unchanged up to one day but it decreased below the control level on the second and third day.

Release of noradrenaline from the cat spleen by nerve stimulation and potassium

1. Release of noradrenaline from the perfused cat spleen, or from isolated spleen slices, in response to prolonged nerve stimulation or maintained depolarization by potassium was measured. 2. Prolonged stimulation of the splenic nerves at 2, 10 and 30 Hz for 10 min evoked release, which was maximum during the first 2 min, and then declined during the remaining period of stimulation. When noradrenaline release was induced by high potassium from the perfused spleen or from isolated slices, it followed a similar time course to nerve stimulation. Similar results were obtained from phenoxybenzamine-treated spleens, using both modes of stimulation. 3. Stimulation of the splenic nerves in calcium-free Krebs solution did not release noradrenaline. If calcium was introduced at a later stage during stimulation, the release was markedly diminished. In phenoxybenzamine- or phentolamine-treated spleens, stimulation of the nerves in the presence of calcium evoked a secretory response which was comparable to the one produced by introduction of calcium after a few minutes of nerve stimulation. 4. Simultaneous application of calcium plus high potassium always produced a much greater secretion of noradrenaline than application of calcium after a few minutes of potassium depolarization. Release of noradrenaline by potassium from phenoxybenzamine-treated spleens was also much greater if calcium and potassium were added simultaneously than addition of calcium after a few minutes of potassium depolarization. 5. In the presence of maintained depolarization by potasssium, tyramine was effective in causing release of noradrenaline.

Effect of castration on the smooth muscle cells of the internal sex organs of the rat: influence of the smooth muscle on the sympathetic neurons innervating the vas deferens, seminal vesicle and coagulating gland

Wet weights of vas deferens, seminal vesicle and coagulating gland were reduced by almost 80 to 90% 10 weeks after castration. Endogenous norepinephrine content and dopamine-beta-hydroxylas activity of these tissues were also reduced to the same degree. One week after castration there was approximately a 50% loss in the weight of all three organs. However, this was accompanied by an equal reduction in norepinephrine content and dopamine-beta-hydroxylase activity only in the vas deferens. Two weeks later the degree of reductions in wet weight, norepinephrine content and dopamine-beta-hydroxylase activity was almost identical for all three organs. Treatment of 40-day castrate rats with testosterone (10 mg/kg s.c.) not only restored the wet weights of the internal sex organs to normal but their norepinephrine content and dopamine-beta-hydroxylase activity as well. Castration of immature rats (10-14 days old) resulted in retardation of growth of the vas deferens and seminal vesicle by 90-95%, and similar reductions in norepinephrin content and dopamine-beta-hydroxylase activity, when compared to the tissues of control littermates on the 90th postoperative day. Histological examination of normal and castrate rats indicated that, along with a reduction in epithelial cells, the smooth muscle cells of the vas deferens, seminal vesicle and coagulating gland was markedly reduce in size as well. Administration of testosterone completely reversed these changes. Furthermore, deoxyribonucleic acid content of the seminal vesicle and coagulating gland was reduced by 50% after castration and then restored to control level after testosterone treatment. Taken together, it seems that atrophy of the internal sex organs following castration is a combined effect of reduction in size and number of smooth muscle cells. Therefore, it is concluded that any alteration in the size of smooth muscle cells or loss of such cells of the internal sex organs indirectly influences their sympathetic nerves in such a manner that norepinephrine concentrations, and thereby the density of innervation, are maintained at normal levels.

On the mechanism of release of norepinephrine from cat spleen slices by sodium deprivation and calcium pretreatment

Endogenous norepinephrine (NE) content of cat spleen slices was markedly depleted by incubating them in a sodium-free solution for 2 hours at 37 degrees C. Dopamine beta-hydroxylase (DBH) activity was not changed by this treatment. During incubation of the slices in sodium-free solution for 30 minutes at 37 degrees C, there was a marked release of NE into the medium without a concomitant release of DBH. Incubation of the slices in a potassium-rich solution (140 mM) resulted in the release of both NE and DBH into the medium. In control slices, the soluble form of DBH accounted for nearly 30 percent of the total DBH activity. The proportion of soluble DBH was not appreciably affected when slices were incubated in sodium-free medium for 2 hours at 37 degrees C. It is concluded that release of NE from sympathetic nerves by sodium deprivation probably occurs by a process other than exocytosis. Additional information is presented concerning the DBH levels in spleen slices which were depleted by their endogenous NE content by preincubation in calcium-rich solution and then in normal Krebs' solution or by a simultaneous inhibition of both glycolytic and oxidative metabolism.

A calcium ionophore stimulating the secretion of catecholamines from the cat adrenal

1. Experiments were performed on perfused cat adrenal glands to examine the effect of a calcium ionophore A-23187 in the secretion of catecholamines. 2. Ionophore (1-10 muM) caused a dose-dependent release of catecholamines and the output was about 100-fold greater at 10 mum than at 1 mum. 3. Release of catecholamines by the ionophore was dependent on the calcium concentration of the perfusion medium. Omission of calcium blocked the response to the ionophore while excess calcium facilitated it. 4. Magnesium antagonized the secretory response to the ionophore. Excess calcium overcame the inhibitory effect of magnesium. 5. The ionophore did not modify release of catecholamines by induced splanchnic nerve stimulation. 6. The results suggest that the ionophore, like depolarization, introduces calcium into the chromaffin cell to cause release of catecholamines.

Release of catecholamines and dopamine beta-hydroxylase from the perfused adrenal gland of the cat

1. Secretion of catecholamines (CA) and dopamine beta-hydroxylase (DBH) activity from the perfused cat adrenal gland was studied following splanchnic nerve stimulation or infusion of acetylcholine (ACh). 2. Splanchnic nerve stimulation (30 Hz) or perfusion with a low concentration of ACh (10-minus5 M) caused a marked release of CA in the venous effluent, but release of DBH activity was minimal while a higher concentration of ACh (10-minus 4 M) enhanced the release of CA and DBH. 3. The ratio of DBH/CA released in the perfusate by splanchnic nerve stimulation or ACh infusion was only a small fraction of the ratio in the soluble lysate of purified chromaffin vesicles. 4. Following reserpine treatment, adrenal CA levels fell to 25% of the control value in 24 hr, remained depressed on days 2, 3, 4 and 5 at 5% of the control and recovered to 60% of the control value on the 6th day. DBH activity was unchanged from the control value at 24 hr after treatment, then rose as high as 5 times the control on the 5th day and was still twice the control value on the 6th day. 5. CA secretion in response to ACh (10-minus 4 M) perfusion was reduced to 30% of the control value on the first day after reserpine treatment, while DBH secretion was unchanged. On the 2nd day, CA secretion was depressed further to 5% of the control and remained at this low level up to 5 days after treatment while DBH secretion was twice the control value at 48 hr and then on days 3, 4 and 5 rose up to 5 times the control value. On the 6th day, secretion of CA recovered to 30% of the control while DBH secretion was now twice the control. 6. Isopycnic sucrose density (discontinuous) gradient centrifugation of vesicles from adrenal glands of control cats, and of cats given reserpine 1 or 2 days perviously, indicated that new vesicles or vesicles depleted of CA by reserpine had a lower equilibrium density than the original population of vesicles. 7. These results suggest that the release of CA is quantal in nature, but the release of DBH is not necessarily coupled with it. Release of DBH by ACh from reserpinized glands suggests that the vesicles which were once involved in secretion may be re-used for synthesis and storage of CA.

Metabolic and ionic requirements for the axoplasmic transport of dopamine beta-hydroxylase

1. Metabolic and ionic requirements for the intra-axonal transport of dopamine beta-hydroxylase (DBH) were investigated in the cat hypogastric nerve-inferior mesenteric ganglion preparation in vitro by monitoring the enzyme accumulation above a crush, 2-2.5 cm distal to the ganglion.2. DBH accumulation in the proximal segment immediately above the crush increased linearly up to 6 h, during incubation in normal Krebs solution at 37 degrees C. The rate of transport of the enzyme was about 4 mm/h.3. Removal of the ganglion, electrical stimulation or reserpine pretreatment (1-6 days before the experiment) did not modify the rate of DBH accumulation.4. Anoxia and glucose deprivation, singly, did not affect accumulation of DBH; however, the combined treatment of anoxia plus glucose deprivation, or dinitrophenol plus glucose deprivation, very markedly interfered with accumulation.5. Removal of sodium or potassium from Krebs solution markedly inhibited the transport of DBH. Preincubation of the nerve in a high-calcium Krebs solution at 4 degrees C, and then reincubation at 37 degrees C, prevented the enzyme accumulation.6. N-ethylmaleimide, ouabain and oligomycin markedly inhibited the transport of DBH.7. The results suggest that transport of DBH, and therefore of noradrenaline storage vesicles, within the hypogastic nerve is dependent on metabolic energy derived from either glycolysis or oxidative phosphorylation. It is also suggested that the sodium-potassium-activated ATPase may play an important role in the intra-axonal transport of storage vesicles.

Thymic hypoplasia due to congenital rubella

Images

Release of noradrenaline from slices of cat spleen by pre-treatment with calcium, strontium and barium

1. Spleen slices pre-incubated for different periods at 4 degrees C in Krebs solution containing varying concentrations of calcium, up to 96 mM, lost their endogenous noradrenaline stores when reincubated in normal Krebs solution at 37 degrees C for 2 hr. Rate of loss of noradrenaline was roughly related to the calcium concentration of the pre-incubation medium and the pre-exposure time.2. Pre-treatment with isotonic barium or strontium (96 mM) Krebs solution also induced release of noradrenaline from spleen slices when re-exposed to normal Krebs solution. Barium was more effective than either calcium or strontium.3. The enhanced release induced by calcium pre-treatment occurred in the absence of calcium, with or without EGTA.4. Tissue calcium concentration of spleen slices was 0.68 m-mole/kg. Pre-treatment of slices with normal or 96 mM calcium-Krebs solution for 4 hr at 4 degrees C increased the calcium concentration to 2.57 and 9.9 m-mole/kg, respectively.5. Ouabain, which caused a dose-dependent release of noradrenaline, did not modify the release induced by calcium pre-treatment.6. Spleen slices prepared from cats anaesthetized with sodium pentobarbitone instead of ether were resistant to noradrenaline depletion by calcium pre-treatment.7. Evoked release of [(3)H]noradrenaline by high potassium from calcium-pre-treated slices did not occur in the absence of external calcium, even though the calcium pre-treatment enhanced the tissue concentration of this ion by nearly tenfold.8. Net uptake of noradrenaline in normal and in treated slices whose noradrenaline content was severely reduced by barium pre-treatment or sodium withdrawal was comparable.9. Specific activity of released and endogenous [(3)H]noradrenaline increased as the tissue stores of noradrenaline were reduced.10. It is suggested that the spontaneous loss of tissue noradrenaline after pre-treatment with high-calcium solution was due to inhibition of sodium-potassium-activated ATPase by intracellular accumulation of calcium ions. Evidence is presented to suggest that vesicles depleted of their endogenous transmitter by pre-treatment with calcium, strontium or barium, or by sodium withdrawal, are re-used for the storage and release of exogenous noradrenaline.

Release of noradrenaline from the cat spleen by sodium deprivation

1. The endogenous noradrenaline content of cat spleen slices was markedly reduced when the slices were incubated at 37 degrees C in a medium in which sodium was replaced by sucrose, lithium, choline or potassium. Depletion of tissue noradrenaline was accounted for by its release into the incubating medium. At an external sodium concentration of 20 mM, about 50% depletion was obtained in 2 hours.2. The enhanced release induced by sodium deprivation occurred in the absence of calcium, with or without ethyleneglycol-bis (beta-aminoethyl ether) N,N' tetraacetic acid. Manganese potentiated release, while magnesium was without effect.3. Ouabain caused a dose-dependent release of noradrenaline which was partially calcium-dependent. Removal of potassium from the incubation medium caused some release, which was potentiated in 25 mM sodium Krebs solution or by ouabain.4. At 4 degrees C, the release did not occur in sodium-free medium.5. Dinitrophenol did not affect the loss of noradrenaline caused by sodium withdrawal. Iodoacetic acid and N-ethylmaleimide caused a time-dependent depletion of noradrenaline. Tetracaine caused release and partly opposed the release caused by sodium deprivation. Tetrodotoxin had no effect. Guanethidine, but not phenoxybenzamine, released noradrenaline and potentiated the release induced by sodium withdrawal.6. The rate of release of (3)H-noradrenaline from reserpine-treated spleen slices was not altered by sodium withdrawal.7. Uptake-retention of (3)H-noradrenaline in slices depleted of their endogenous noradrenaline content by sodium deprivation was about 60% of the control slices. This was effectively blocked by cocaine. Release of (3)H-noradrenaline evoked by high potassium from both control and treated slices was calcium-dependent.8. It is suggested that sodium-potassium-activated ATPase maintains the integrity of the axonal membrane, and any procedure which depresses the activity of the enzyme or the sodium-potassium pump would cause transmitter release by causing temporary disturbance in the membrane. Evidence is presented to suggest that vesicles depleted of their endogenous noradrenaline content by sodium deprivation are re-used for the storage and release of transmitter.

Congenital toxoplasmosis in two successive sibs

Images