Observations on the localization of recently synthesized catecholamines in chromaffin cells after the injection of L-(2,5,6-3H)dopa

Carbon-Fiber Nanoelectrodes for Real-Time Discrimination of Vesicle Cargo in the Native Cellular Environment

Carbon-fiber microelectrodes have proven to be an indispensable tool for monitoring exocytosis events using amperometry. When positioned adjacent to a cell, a traditional microdisc electrode is well suited for quantification of discrete exocytotic release events. However, the size of the electrode does not allow for intracellular electrochemical measurements, and the amperometric approach cannot distinguish between the catecholamines that are released. In this work, carbon nanoelectrodes were developed to permit selective electrochemical sampling of nanoscale vesicles in the cell cytosol. Classical voltammetric techniques and electron microscopy were used to characterize the nanoelectrodes, which were ∼5 μm long and sharpened to a nanometer-scale tip that could be wholly inserted into individual neuroendocrine cells. The nanoelectrodes were coupled with fast-scan cyclic voltammetry to distinguish secretory granules containing epinephrine from other catecholamine-containing granules encountered in the native cellular environment. Both vesicle subtypes were encountered in most cells, despite prior demonstration of populations of chromaffin cells that preferentially release one of these catecholamines. There was substantial cell-to-cell variability in relative epinephrine content, and vesicles containing epinephrine generally stored more catecholamine than the other vesicles. The carbon nanoelectrode technology thus enabled analysis of picoliter-scale biological volumes, revealing key differences between chromaffin cells at the level of the dense-core granule.

Neural regulation of adrenal chromaffin cell function in the mouse: fate and distribution of [3H]dopamine in denervated adrenal medulla

The distribution and time course of appearance and decline of radioactivity in denervated adrenal medulla of mice injected with [3H]dopamine was examined by autoradiography. Radioactivity irradiated from [3H]dopamine was increased from 7.5 min to 30 min, then decreased rapidly in both adrenaline-storing (A) cells and noradrenaline-storing (NA) cells of either intact or denervated adrenals. In subcortical A cells, the incorporation of radioactivity was increased by denervation while in NA cells and in A cells in the center of the medulla, the increment was not significant. In the denervated adrenals, the decline of [3H]dopamine-derived radioactivity was slower than that in the intact gland. The denervation increased the gradient in radioactivity from the surface to the center of the medulla. The present results suggest that the sensitivity to neuronal suppression of dopamine uptake in subcortical A cells is different from that in A and NA cells in the rest of the gland. The results also indicate a functional heterogeneity within a single type of chromaffin cells.

Uptake of [3H]2-deoxy-D-glucose and [3H]dopamine in adrenal chromaffin cells of the mouse

Deoxyglucose method was applied to adrenal chromaffin cells. It was shown that dichromate-fixation could fix [3H]deoxyglucose in tissue sections. Dichromate-fixation has two advantages as compared with glutaraldehyde-fixation: (1) two types of adrenal chromaffin cells, adrenaline-storing (A) cell and noradrenaline-storing (NA) cells, are distinguishable, (2) more [3H]deoxyglucose is retained in sections than in those fixed with glutaraldehyde. No difference was demonstrated in the uptake of deoxyglucose between A and NA cells while A cells incorporated more [3H]dopamine than NA cells. This indicates that such difference was not due to the different rate of glucose utilization.

On the uptake and storage of 5-hydroxytryptamine, 5-hydroxytryptophan and catecholamines by adrenal chromaffin cells and nerve endings

Light-microscopic autoradiographs of the adrenal medulla at various intervals after the intravenous injection of [3H] 5-HTP, [3H] 5-HT, [3H] noradrenaline and [3H] adrenaline have been studied. The distribution of silver grains following [3H] 5-HTP uptake was found to be uniform over each of the two main cell populations, adrenaline-storing (A) cells and noradrenaline-storing (NA) cells in the adrenal medulla, but A cells were twice as active as NA cells in incorporating the isotope, a situation very similar to that found after [3H] dopa uptake. 5-HT administration resulted in a pattern resembling the distribution of [3H] noradrenaline uptake, with A cells being 4 or 5 times more active than NA cells and a gradient of activity from the periphery of the medulla inwards. However, the time-course for the loss of radioactivity was not the same for both amines: levels of 5-HT activity were not significantly reduced after one week whereas the degree of [3H] noradrenaline labelling after one week was less than 10% of that at one hour. Thus 5-HT may be bound to sites in the adrenal medulla normally occupied by noradrenaline but it would appear that the release mechanism is different. There was no evidence of 5-HT uptake by adrenal nerve endings.

Multiple endocrine neoplasia syndromes

The multiple endocrine neoplasia (MEN) syndromes are characterized by autosomal dominant inheritance with a high degree of penetrance but varying expression. This review gives a classification of these syndromes and a short summary of the historical background. The pathogenesis of the disease and its possible origin in the APUD cell system are discussed together with the mechanisms underlying normal and ectopic hormone production by MEN tumors on the basis of recent findings in molecular endocrinology. The natural history and the clinical manifestations of the different syndromes are described. The sensitivity and discriminative capacity of the tests used to detect the syndromes in an early stage are compared. The choice of therapy and criteria for the timing and extensiveness of treatment are also considered. Lastly, problems associated with the ethical and legal aspects of screening, central registration, and monitoring of relatives at risk are described.

Neural regulation of adrenal chromaffin cell function in the mouse--stress effect on the distribution of [3H]dopamine in denervated adrenal medulla

Effects of adrenal denervation and stress on the distribution of radioactivity in the adrenal medulla after [3H]dopamine injection was studied by light microscopic autoradiography. Denervation of the adrenal gland abolished the stress (restraint plus water immersion) induced degranulation of adrenal chromaffin cells and decreased uptake of [3H]dopamine. Denervated chromaffin cell of stress mice incorporated as high radioactivity as those of no stress mice. Adrenal denervation increased the uptake in adrenaline-storing (A) cells but not in noradrenaline-storing (NA) cells. The characteristic distribution of radioactivity (high radioactivity along the cortico-medullary junction) was reinforced by adrenal denervation. Under stress conditions, increase in pituitary adrenocortical system did not enhance the uptake of [3H]dopamine in chromaffin cell while increase in nerve activity suppressed the uptake. Spontaneous activity of the splanchnic nerve to adrenal chromaffin cells suppresses the uptake of [3H]dopamine. The neural influence is stronger on A cells than on NA cells. Chromaffin cells in the subcortical zone are more intensely controlled by the neural influence than those in the central zone.

On the uptake of exogenous catecholamines by adrenal chromaffin cells and nerve endings

Light-microscopic autoradiography has revealed characteristic labelling patterns in adrenal medullary cells following the intravenous administration of different catecholamines. The uptake patterns for [3H] dopa, [3H] dopamine, [3H] noradrenaline and [3H] adrenaline ahve been compared. In all cases A cells were more active than NA cells and cells situated in the zone nearest the cortex demonstrated a markedly higher rate of uptake than central cells. It was concluded that adjacent chromaffin cells with very similar morphology may differ as much as 50 fold in their capacities to incorporate exogenous amines. The adrenergic nature of te innervation of the vessels of the adrenal cortex and capsule in the mouse was confirmed.

Bilateral occurrence of pheochromocytoma in patients with the multiple endocrine neoplasia syndrome type 2A (Sipple's syndrome)

Two kindreds with the multiple endocrine neoplasia type 2A syndrome were studied. Of one of these we examined 150 members, 20 of whom were treated with thyroidectomy for medullary carcinoma and nine with bilateral adrenalectomy for pheochromocytoma. Of the second kindred 50 members were examined, seven of whom were thyroidectomized and seven treated with bilateral adrenalectomy. Pheochromocytomas were invariably found on both sides, even in four cases in which the adrenals on one side appeared to be completely normal, not only at preoperative roentgenologic examination but also on inspection during the operation. The microscopic finding of micronodules and a cluster of abnormal medullary cells identical with those found in pheochromocytomas in one of the apparently normal adrenals represents a first stage in the development of diffuse medullary hyperplasia as well as nodular hyperplasia. This is in accordance with the fact that in the MEN type 2A syndrome pheochromocytomas are always multicentric and multiple in origin. On the basis of these findings we conclude that all patients with the MEN 2A syndrome who show symptoms and signs of active pheochromocytoma should be subjected to bilateral adrenalectomy, even when one or both of the adrenals appear to be normal at roentgenologic investigation.