Rapid and Fine Adjustment of Corticosteroidogenesis Operating in the Adrenal Gland of the Mongolian Gerbil (Meriones unguiculatus) Superfused In-Vitro

Summary

Corticosteroid release from adrenals of male adult Mongolian gerbils (Meriones unguiculatus) has been studied during continuous and discontinuous in-vitro superfusion. Corticosteroid output from glands of untreated animals with plasma corticosteroid levels below 300 ng/ml was 3.3 ± 0.3 ng/adrenal pair/min and decreased only slightly with the length of superfusion (60 min: 3.1 ± 0.3 ng/adrenal pair/min). In-vitro secretion was significantly higher from-adrenals of animals which had corticosteroid plasma levels of over 300 ng/ml, underwent clonic-tonic seizures, or were injected with 6 IU/animal (1—24) ACTH. On the other hand, injection of 2 × 50 μg dexamethasone markedly decreased corticosteroid plasma levels but had no significant effect on in-vitro secretion of corticosteroids.

In contrast to the slow and small, but long-lasting stimulation of corticosteroid secretion elicited by (1—24) ACTH, secretion could be changed within much shorter time periods, either by the addition of plasma proteins to superfusion medium or by stops of superfusion flow. While a significant stimulation of corticosteroid output occurred after the addition of 1% or 10% BSA or rat plasma, stops of superfusion flow for 1,5 or 10 min resulted in a strong inhibition of steroidogenesis, as is evident from corticosteroid amounts found in the first 1-min samples after re-start of superfusion. Within 4—5 min after re-start of superfusion, secretion returned to basal values. Corticosteroid amounts secreted from adrenals superfused in-vitro were significantly higher than those secreted from adrenals incubated in-vitro. In addition, prolonged incubation suppressed corticosteroidogenesis (30 min: 100%, 60 min: 64%, 90 min: 56%, 120 min: 59%).

The results demonstrate that superfusion of sliced adrenal tissue gives insights into aspects of adrenal function, including the rapid changes in synthesis and secretion after flow stops which cannot be investigated by incubation of either tissue slices or isolated cells. The possibility that the observed decline in corticosteroidogenesis during flow stops may be due to a feedback inhibition resulting from corticosteroids accumulating within slices is discussed.

Key words

Mongolian gerbil - Corticosteroidogenesis - (1—24) ACTH - Flow stop