Fine structure of adrenocortical cells in adult male rhesus monkeys

Adrenals of ten mature male rhesus monkeys were studied by electron microscopy. Mitochondria had lamelliform cristae in the zona glomerulosa and tubular cristae in the zona fasciculata and zona reticularis. Agranular reticulum of tubular form was scarce in the zona glomerulosa but present in great abundance in the fasciculata and reticularis. The Golgi complex was prominent in the cells of the zona glomerulosa but poorly developed in the cells of the inner cortical zones. Zona fasciculata cells contained large, highly ordered “stacks” of granular endoplasmic reticulum which showed multiple connections with the random network of tubular agranular reticulum. In the reticularis, granular endoplasmic reticulum was present in more disordered, whorl-like arrays. Lipid droplets in the inner cortical regions were enveloped by tubules of agranular endoplasmic reticulum. Occasional sections showed these tubules ending blindly at or near the surface of the lipid droplets. This association was strongly suggestive of a functional relationship. Dense bodies varied in size and complexity of structure throughout the cortex. They were smallest and simplest in form in the zona glomerulosa; those in the zona reticularis were the largest and most complex.