Co-Culture of Amphibian Adrenal Cells: A Model of Medullary Control of Corticosteroidogenesis
Shepherd, Stacie Peacock
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Permalink
https://hdl.handle.net/2142/82540
Description
Title
Co-Culture of Amphibian Adrenal Cells: A Model of Medullary Control of Corticosteroidogenesis
Author(s)
Shepherd, Stacie Peacock
Issue Date
1999
Doctoral Committee Chair(s)
Holzwarth, Matilde
Department of Study
Neuroscience
Discipline
Neuroscience
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Language
eng
Abstract
Chromaffin-adrenocortical cellular interactions have become recognized as an important component of adrenocortical regulation, however, the mechanisms by which chromaffin cells modulate adrenocortical function are not well understood. To study chromaffin-adrenocortical cellular interactions directly, we developed primary frog (Rana pipiens) adrenal co-cultures. In these co-cultures, chromaffin cells extend processes that project toward or onto adrenocortical cells, mimicking their organization in vivo and indicating a potential for interaction between the two cell types. Furthermore, cultured chromaffin cells secrete norepinephrine, epinephrine and serotonin and respond to carbamylcholine, potassium, and veratridine stimulation; adrenocortical cells secrete a1dosterone and corticosterone and retain ACTH-responsiveness. To test whether chromaffin cells affect adrenocortical steroidogenesis, we used veratridine to selectively activate chromaffin cells. Prolonged chromaffin cell activation (24--96 hr) using 50 muM veratridine increased the number of contacts between chromaffin and adrenocortical cells and increased corticosterone secretion on days 3 (950%), and 4 (350%). alpha 2- and beta1,2-adrenergic and dopaminergic antagonists decrease corticosterone and aldosterone secretion while alpha2- and beta1,2-adrenergic agonists increase steroid secretion, suggesting that catecholamines mediate chromaffin-adrenocortical cellular interactions via these adrenergic receptor subtypes. Adrenocortical cell Fos protein expression was increased by chromaffin cell activation with 2 mM carbamylcholine (37%) or 50 muM veratridine (25%), demonstrating that chromaffin cell activation affects adrenocortical cells at the transcriptional level. The dynamic behavior of chromaffin and adrenocortical cells was assessed using time lapse microscopy. The effects of chromaffin cell activation on chromaffin cell morphology were evident within 30 minutes of verutridine treatment and included the establishment of growth cones, varicosities and rounded soma. Additionally, significant neurite outgrowth and branching, most often toward adrenocortical cells, was routinely observed, in contrast to control cultures. In both control and veratridine-treated cultures, substantial migration of adrenocortical cells towards chromaffin cells occurred, suggesting the presence of a trophic factor originating in the neuronal cells. Our results provide further evidence for reciprocal interactions between chromaffin and adrenocortical cells that affect cellular differentiation and modulation of steroid secretion. Furthermore, chromaffin and adrenocortical cells show activity-related plasticity that is likely to be important during development and in maintaining homeostasis.
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