Regulation of Steroidogenesis by ACTH in a Superfusion System for Isolated Adrenal Cells

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Abstract
Isolated adrenal cells in suspension have been continuously superfused for several hours using a counter-streaming centrifuge technique. Cells were held in a conical tube rotated in a horizontal plane at low speed (10–40 g) and medium introduced at the apex of the tube was allowed to flow towards the neck of the tube and the axis of rotation. The cells were retained in suspension in a conical tube by counterbalancing the outward centrifugal force on each cell against the opposing viscous force of the liquid stream. The effects of injections of single doses and continuous infusions of ACTH were examined and the dynamic responses studied. The latent period of response to ACTH was estimated at 2–3 min, and the time required to achieve maximal rate of steroidogenesis at about 12 min. Following a single pulse of ACTH, the steroidogenic response decayed exponentially with a half-life of about 10 min. A decline in steroid output during later time periods of continuous infusions of ACTH to superfused adrenal tissue fragments has been previously observed. The possibility that this decline was due to a feed-back inhibitory effect resulting from corticosteroid accumulation within the blocks of superfused tissue has been eliminated, following the observation that a similar late decline (half-life: 41 min) in corticosteroid output rate occurred using superfused isolated adrenal cells continuously infused with ACTH. This technique, combining the advantages of the isolated cell suspension and the superfusion system, provides a valuable tool for studying the dynamic functioning in vitro of endocrine control mechanisms and is applicable to a. wide variety of discrete cell types for examining their acute responses in suspension to infusions of regulatory factors. (Endocrinology93: 700, 1973)

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