Bromocriptine-induced removal of endoplasmic membranes from prolactinoma cells

Landolt, Alex M.; Osterwalder, V.; Landolt, T. A.

doi:10.1007/bf02007698

Cited by 12 publications

(11 citation statements)

References 16 publications

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“…In a detailed study, Landolt et al [14] forwarded evidence in support of the former hypothesis. However, the in crease in lysosomal volume density, demonstrated in all but 1 of our cases, suggests that autophagy may play a role in the observed cellular involution.…”

Section: Discussionmentioning

confidence: 62%

“…In addition, light microscopic morphome try demonstrates that the overall reduction in cell size is largely attributable to reduced cytoplasmic volume. Sim ilar findings have been obtained in vivo [5][6][7][8][9], leading to the assumption that cytoplasmic depletion is probably a consequence of a reduction in the size of ER and Golgi apparatus [6,14], The present study reveals that ER and Golgi apparatus are the only organelles with consistently reduced cytoplasmic volume densities after treatment. Since dopaminergic agonists, such as bromocriptine, in hibit the synthesis as well as the release of prolactin in rat prolactin cell adenomas [15,16], it is reasonable to assume that similar effects are exerted on human prolac tin cell adenomas.…”

Section: Discussionmentioning

confidence: 65%

“…Morphometric analysis of prolactin cell adenomas treated with bromo criptine in vivo reveals no change [6] or a reduction [17] in lysosomal material. Landolt et al [14] claim that cell size reduction is the result of increased discharge of lysosomal material from the cell to the intercellular space. This, however, does not exclude the possibility that lysosomal degradation of cytoplasmic components may be a contributing factor to the ensuing cell involu tion and there is considerable in vivo proof of lyso somal accumulation in cells treated with bromocriptine for more than 7 days [2,5,8].…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Bromocriptine on Secretion and Morphology of Human Prolactin Cell Adenomas in vitro

Duffy

Sylvia²,

Kovács³

1988

Horm Res

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The direct effect of short-term bromocriptine administration on human prolactin cell adenomas in vitro was studied by light and electron microscopy and correlated with the effect on hormone release. The light microscopic and, for the first time, ultrastructural characteristics of adenomatous prolactin cells in control and treated cultures were analyzed morphometrically and the changes induced by bromocriptine were quantified. Following 72 h treatment which lowered levels of prolactin release, there was a marked reduction in cell size, cytoplasmic volume and cytoplasmic volume densities of endoplasmic reticulum and Golgi apparatus. In contrast, the percentage of cytoplasm occupied by lysosomes increased. There was no consistent change in number and diameter of secretory granules. These findings indicate that prolactin cell involution is a direct effect of bromocriptine and suggest that reduction in endoplasmic reticulum and Golgi complex is largely responsible for the decreased cell size. Lysosomal degradation of cytoplasmic components may play a role in this process.

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Section: Discussionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 65%

Section: Discussionmentioning

confidence: 99%

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Effect of Bromocriptine on Secretion and Morphology of Human Prolactin Cell Adenomas in vitro

Duffy

Sylvia²,

Kovács³

1988

Horm Res

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“…A further ef fect of bromocriptine was the virtual elimination of cells with electron-dense cytoplasm and greatly dilated ER ('dark' cells) which were a prominent feature during es trogen withdrawal. Bromocriptine-induced loss of ER has been described in prolactin cells [26,27], but the re duction in numbers of 'dark' cells after 2 h exposure to bromocriptine is difficult to explain. The role of these cells is unknown [28].…”

Section: Discussionmentioning

confidence: 99%

Apoptosis in the Anterior Pituitary Gland of the Rat: Studies with Estrogen and Bromocriptine

Drewett¹,

Jacobi²,

Willgoss³

et al. 1993

Neuroendocrinology

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Apoptosis was investigated by electron and light microscopy in the anterior pituitary gland of the male Fischer rat in which hyperplasia of prolactin-secreting cells had been induced by estrogen implanted subcutaneously for 6 weeks. Counts by light microscopy of apoptotic cells and cells containing phagocytosed apoptotic bodies increased during a period of 44 h after estrogen withdrawal. Necrosis was present but was not prominent. Administration of bromocriptine after estrogen withdrawal increased apoptotic counts to nearly double those in the absence of bromocriptine. Bromocriptine caused some increase in necrosis. Apoptosis occurred in prolactin-secreting cells identified by immunostaining and in other cells. Phagocytosed apoptotic bodies were seen in folliculo-stellate and not in other cells. It is concluded that apoptosis occurs in the anterior pituitary gland and is induced by bromocriptine. Phagocytosis of apoptotic bodies is a function of the folliculo-stellate cells.

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“…Several reports have suggested that tumor regression induced by bromocriptine therapy is at least partially due to a reduction in cell size of prolactinoma cells [46, 47, 48]. The reduction in cell size by bromocriptine may be attributable to a rapid involution of rough endoplasmic reticulum and Golgi apparatus, as demonstrated by ultrastructural studies [46, 47, 49]. It is tempting to speculate that the dopaminergic action on cell shape and actin organization, as shown in serum-free culture in the present study, is responsible for the reduction in cell size of bromocriptine-treated human prolactinoma cells although it is not yet investigated by other cultures with serum-containing medium whether the dopaminergic action on cell shape can be reproduced universally in vitro.…”

Section: Discussionmentioning

confidence: 99%

D<sub>2</sub> Dopamine-Receptor-Mediated Inhibition of Proliferation of Rat Lactotropes in Culture Is Accompanied by Changes in Cell Shape

Hashi²,

Hoshi³

et al. 1998

Neuroendocrinology

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Dopaminergic agonists are effective in vivo in inhibiting lactotrope proliferation and prolactin (PRL)-secreting pituitary tumors. The purpose of the present study was to demonstrate in vitro actions of dopaminergic agents on proliferation and cell shape of rat lactotropes. Anterior pituitary cells cultured with serum-free, chemically defined medium were treated with dopaminergic agents and were labeled with 5-bromo-2′-deoxyuridine (BrdU) for 3 h before the end of culture. BrdU-labeling indices indicative of the proliferation rate of lactotropes were determined by double immunofluorescence staining for BrdU and PRL. Treatment with dopamine for 21 h decreased BrdU-labeling indices of lactotropes in a dose-dependent manner with a nadir at 3 × 10^–7 M. The inhibitory action of 10^–5 M dopamine appeared 15 h after the initiation of treatment and became pronounced with time up to 33 h. The dopamine action was mimicked by treatment with the D₂ receptor agonist bromocriptine at concentrations over 10^–9 M. Phase-contrast microscopy revealed that the flat polygonal cell shape of cultured lactotropes had changed to a round refractive cell shape after treatment with dopamine or bromocriptine, and that these changes in cell shape exactly paralleled those in the BrdU-labeling index. The changes in cell shape of lactotropes were accompanied by changes in subcellular distribution of actin filaments. Pretreatment with 10^–7 M eticlopride, a D₂ receptor antagonist, blocked the dopamine- or bromocriptine-induced changes in both BrdU-labeling index and cell shape. These results suggest that (1) the in vitro experimental system established in the present study is a good model for studying the mechanism of the antiproliferative action of dopamine and (2) D₂-receptor-mediated inhibition of proliferation of lactotropes in serum-free culture is closely related to changes in actin organization and cell shape.

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Bromocriptine-induced removal of endoplasmic membranes from prolactinoma cells

Cited by 12 publications

References 16 publications

Effect of Bromocriptine on Secretion and Morphology of Human Prolactin Cell Adenomas in vitro

Effect of Bromocriptine on Secretion and Morphology of Human Prolactin Cell Adenomas in vitro

Apoptosis in the Anterior Pituitary Gland of the Rat: Studies with Estrogen and Bromocriptine

D<sub>2</sub> Dopamine-Receptor-Mediated Inhibition of Proliferation of Rat Lactotropes in Culture Is Accompanied by Changes in Cell Shape

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