Functional and structural differences between cultured outer and inner layer cells of bovine adrenal cortex.

Outer and inner layer cells of bovine adrenal cortex were cultured separately to compare cellular structural characteristics and functional differences. Outer layer cells were polygonal in shape with radially distributed lipid droplets in the cytoplasm, and produced mainly aldosterone and cortisol. The aldosterone production increased upon stimulation with angiotensin II or dibutyryl-cAMP. In contrast, inner layer cells were spindle-shaped and had fine diffused lipid droplets. They produced four times as much cortisol as outer layer cells but no aldosterone. Cortisol production increased with ACTH or dibutyryl-cAMP stimulation. When stimulated by ACTH or by dibutyryl-cAMP, both types of adrenocortical cells showed "cellular retraction" whereby the number of cytoplasmic lipid droplets decreased and microvilli on the cellular surface increased. At the same time, the transverse distribution of actin fibers disappeared and the microtubules changed their distribution pattern from circular to radial. Stimulation by angiotensin II, on the other hand, brought no marked structural changes. These results indicate that, in functional terms, the outer layer cells and the inner layer cells in this culture system reflect zona glomerulosa and zona fasciculata-reticularis, respectively.