Enhancement of adrenomedullary catecholamine release by adrenal cortex in fetus

Catecholamines (CA) release from ovine fetal adrenomedullary cells was greatly enhanced by coincubation with adrenocortical cells. Total CA release was significantly elevated at 2 and 6 h of preincubation by seven- and twofold, respectively. With continuous coincubation of the two cell types, the enhancement of release was found to occur as early as 30 min and maintained for at least 6 h. A similar enhancement effect was observed when adrenomedullary cells were incubated in adrenocortical cell incubation medium (ACM). The stimulation of release was demonstrated for each of the three CA: dopamine, norepinephrine, and epinephrine. The effect of adrenocortical cells differed from that of adrenal steroids, because cortisol selectively stimulated the release of epinephrine only by one- to threefold after a latency of 6 to 9 h, whereas dehydroepiandrosterone had no effect on the release of the three CA at any time tested. Finally, the CA stimulatory activity in ACM was acid and heat stable, not extractable by ether but inactivated by proteolytic digestion. These results suggest that the adrenal cortex of the near-term ovine fetus secretes a factor that stimulates the release and perhaps synthesis of CA from the adrenal medulla.