In vitro modification of rat adrenal zona fasciculata/reticularis function by the zona glomerulosa.

Following earlier findings, the possibility that the zona glomerulosa of the rat adrenal cortex may modify inner zone function was investigated. In a series of in vitro experiments designed to test this hypothesis it was found that: 1. Inner zone preparations gave significantly more steroid than either glomerulosa tissue incubated alone, or (for the first 40 min of a two hour incubation), an equivalent amount of whole adrenal tissue. Whole tissue yields were greater than glomerulosa alone only at the 120 min point. At no time did the whole tissue output approach the total anticipated by addition of separate inner zone and glomerulosa yields. 2. In 20 min incubations, inner zone steriod output generally could be depressed by the addition of a glomerulosa preincubation medium (PIM), or a steroid extract of a glomerulosa PIM, or by the addition of 100 ng aldosterone. Inner zone PIM had less effect. 3. Higher concentrations of aldosterone gave increased inhibition of inner zone corticosteroid production. The results indicated that only a part of the total corticosterone output was aldosterone sensitive in this way. 4. More specific analysis of the steroids showed that yields of corticosterone from endogenous precursors were depressed by aldosterone, but deoxycorticosterone and 18-hydroxydeoxycorticosterone were not. In the same incubations the presence of aldosterone had no effect on the formation of these three products from [3H]pregnenolone. In total the results suggest that the presence of the glomerulosa may affect inner zone function by inhibiting the secretion of corticosterone formed from endogenous precursors. It is possible that aldosterone is the agent of this effect.