Corticosteroidogenesis in the isolated Mongolian gerbil adrenal gland during continuous and discontinuous superfusion

Corticosteroid (C) release by adrenals of male Mongolian gerbils (Meriones unguiculatus) has been studied during continuous and discontinuous (flow stop) superfusion. Flow stops of superfusion for 1, 5, 10 or 20 min resulted in a significant accumulation of C within adrenal tissue and superfusion flask. Amounts of C in the first 2-min samples after re-start of superfusion were positively correlated with the amounts secreted during continuous superfusion (5 min: r = 0.97, 10 min: r = 0.97, 15 min: r = 0.74, 20 min: r = 0.84, all p less than 0.001) and with the length of flow stops (1-20 min: r = 0.92, p less than 0.001). However, C concentrations in superfusates were significantly lower than values calculated from secretion during continuous superfusion and the length of flow stops (0 min = 100%, 1 min: 92%, 5 min: 65%, 10 min: 49%, 15 min: 39%, 20 min: 35%). As is evident from the very similar C amounts secreted by adrenals incubated for 15 min without or with 95%O2/5%CO2 (234 vs 256% of basal secretion), flow stop-induced inhibition of corticosteroidogenesis was not due to a lack of oxygen during flow stops. The results demonstrate that superfusion of sliced adrenal tissue gives insights into regulatory mechanisms, including the rapid changes of corticosteroidogenesis during short-lasting flow stops, which cannot be studied in static incubation of either tissue slices or isolated cells. The possibility that the observed decline in steroidogenesis during flow stops may be due to a local feedback inhibition resulting from C accumulating in the microenvironment of adrenal cells is discussed.