Stimulus—secretion coupling in a neurosecretory organ: the role of calcium in the release of vasopressin from the neurohypophysis

Douglas, W. W.; Poisner, Alan M.

doi:10.1113/jphysiol.1964.sp007399

Cited by 471 publications

(166 citation statements)

References 24 publications

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“…a calcium channel similar to the "late" calcium channel described in the squid axon (Baker et al, 1973) inasmuch as Mn 2+, Co 2+, and D600 were shown to block the potassium-induced calcium uptake and hormone release (Dreifuss et al, 1973). Furthermore, potassium-induced depolarization of the neural lobe in Na-free media gives rise to the release of a large amount of vasopressin (Douglas and Poisner, 1964 a). This suggests that during depolarization of the membrane, calcium channels in the terminal are activated, resulting in a calcium influx and hormone release.…”

Section: Discussionmentioning

confidence: 99%

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Effects of veratridine on Ca fluxes and the release of oxytocin and vasopressin from the isolated rat neurohypophysis.

Nordmann¹,

Dyball²

1978

The Journal of General Physiology

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A B S T R A C T Uptake of radioactive calcium, 4~Ca efflux, and hormone release from the isolated rat neurohypophysis were monitored in vitro after the addition of veratridine to the incubation medium. Veratridine dramatically increased hormone release, but the release rate was not sustained and had declined by about 90% after 2 h. Removal of external Na § prevented hormone release as did addition to the incubation medium of tetrodotoxin or the calcium antagonists D600 and Mn z+ ions. Veratridine increased 45Ca uptake into the isolated neurohypophysis and the increase could be prevented by addition of tetrodotoxin or D600 to the medium. Efflux of 4SCa was not changed by addition of veratridine. The results underline the importance of both Na + and Ca +2 channels in the regulation of secretion of neurosecretory products.

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Section: Discussionmentioning

confidence: 99%

“…Douglas and Poisner (1964 a) showed that depolarized neurohypophyses release neurohormones only in the presence of external calcium ions. They also showed that hormone release is associated with an uptake of extracellular calcium (Douglas and Poisner, 1964 b).…”

Section: Discussionmentioning

confidence: 99%

Effects of veratridine on Ca fluxes and the release of oxytocin and vasopressin from the isolated rat neurohypophysis.

Nordmann¹,

Dyball²

1978

The Journal of General Physiology

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“…In this process Ca z+ ions were believed to play an important role since Ca 2+ ions are required in the extracellular fluid to stimulate a secretory cell successfully [25,27,35,37,52]. Later from flux measurements in different systems it was concluded that an increase of intracellular Ca 2 + may be necessary for the transformation of the stimulus into release of secretory products [13,23,24,26,36,48,49].…”

Section: Discussionmentioning

confidence: 99%

Fusion of secretory vesicles isolated from rat liver

Gratzl

Dahl

1978

J. Membrain Biol.

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Summary. Secretory vesicles isolated from rat liver were found to fuse after exposure to Ca 2 +. Vesicle fusion is characterized by the occurrence of twinned vesicles with a continuous cleavage plane between two vesicles in freeze-fracture electron microscopy. The number of fused vesicles increases with increasing Ca 2 +-concentrations and is half maximal around 10 -6 M. Other divalent cations (Ba 2+, Sr 2+, and Mg 2+) were ineffective. Mg 2+ inhibits Ca2+-induced fusion. Therefore, the fusion of secretory vesicles in vitro is Ca z+ specific and exhibits properties similar to the exocytotic process of various secretory cells.Various substances affecting secretion in vivo (microtubular inhibitors, local anesthetics, ionophores) were tested for their effect on membrane fusion in our system.The fusion of isolated secretory vesicles from liver was found to differ from that of pure phospholipid membranes in its temperature dependence, in its much lower requirement for Ca 2+, and in its Cag+-specificity. Chemical and enzymatic modifications of the vesicle membrane indicate that glycoproteins may account for these differences.Membrane fusion is an essential event in a variety of cell functions such as cell fusion, uptake of extracellular material (endocytosis) and release of cell products (exocytosis). Elucidation of the molecular mechanism of membrane fusion has been hampered by the lack of suitable systems for studying this process. Studies with intact cells have not yielded data which lead to ready interpretation concerning subcellular processes. On the other hand, studies with artificial membranes may be only tangentially related to the fusion of biological membranes.Recently our group investigated the fusion of isolated biological membranes [16,17,31,33,69,74]. We observed that Ca 2+ specifically induces the fusion of isolated secretory vesicles in a buffered sucrose medium.Intervesicular fusion of secretory vesicles, as well as the interaction between the cell membrane and the vesicle membrane, was observed in a variety of secretory cells [2,3,6,18,29,39,53,65]. Douglas [20] showed that in "compound exocytosis" by mast cells an external stimulus initiates fusion between secretory vesicle membranes and the

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“…These molecules are carried down their axons to be released into the capillary circulation of the posterior pituitary gland (e.g. Douglas & Poisner 1964, Bargmann 1966. From there, they enter the general circulation to reach their distant target organs -the kidney and the reproductive smooth muscle.…”

Section: Introductionmentioning

confidence: 99%

60 YEARS OF NEUROENDOCRINOLOGY: MEMOIR: Geoffrey Harris and my brush with his unit

Raisman

2015

Journal of Endocrinology

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Geoffrey Harris is chiefly known for his demonstration of the control of the pituitary gland by the portal vessels coming from the hypothalamus. This does not do justice to his extraordinary contribution to biology. Harris' life's work was central in demonstrating the brain/body interactions by which animals and humans adapt to their environment, and above all the control of that most crucial and proximate of all evolutionary eventsreproduction. In this brief review, I have tried to put Geoffrey Harris' work in the context of the scientific thinking at the time when he began his work, and above all, the contribution of his mentor, FHA Marshall, on whose towering shoulders Harris rose. But this is mainly my personal story, in which I have tried to show the debt that my work owed to Harris and especially to my dear friend, the late Keith Brown-Grant in Harris' team. I myself was never an endocrinologist, but over a short period in the early 1970s, under the influence of such inspirational mentors, and using purely anatomical methods, I was able to demonstrate sexual dimorphism and hormone-dependent sexual differentiation in the connections of the preoptic area, regeneration of the median eminence, the ultrastructure of apoptosis, the requirement for the suprachiasmatic nuclei in reproductive rhythms, the existence of non-rod or cone photoreceptors in the albino rat retina and, later, the expression of vasopressin by solitary (one in 600) magnocellular neurons in the polydipsic di/di Brattleboro mutant rat; this phenomenon was subsequently shown to be due to aC1 reading frameshift. I end this brief overview by mentioning some of the abiding and fascinating mysteries of the endocrine memory of the brain that arise from Harris' work on the control of the endocrines, and by pointing out how the current interest in chronobiology emphasises what a Cinderella the endocrine mechanisms have become in current brain imaging studies.

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Stimulus—secretion coupling in a neurosecretory organ: the role of calcium in the release of vasopressin from the neurohypophysis

Cited by 471 publications

References 24 publications

Effects of veratridine on Ca fluxes and the release of oxytocin and vasopressin from the isolated rat neurohypophysis.

Effects of veratridine on Ca fluxes and the release of oxytocin and vasopressin from the isolated rat neurohypophysis.

Fusion of secretory vesicles isolated from rat liver

60 YEARS OF NEUROENDOCRINOLOGY: MEMOIR: Geoffrey Harris and my brush with his unit

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