The andrenocortical homolog in the lake sturgeon, acipenser fulvescens rafinesque.

The adrenocortical homolog in the chondrostean fish, Acipenser fulvescens, is confined within yellow corpuscles located at the dorsal junction of the two kidneys near the cardinal veins. The concentration and distribution of this tissue in chondrosteans appear to be a condition intermediate between that of cyclostomes and teleosts. The homology of this tissue to adrenocortical tissue of higher vertebrates is demonstrated in its delta5-3beta-hydroxysteroid dehydrogenase activity and the ultrastructure of the cells. The cells contain large lipid droplets and an abundance of smooth endoplasmic reticulum and mitochondria. The abundance of smooth endoplasmic reticulum, a large Golgi apparatus and an extensive elaboration of the plasma membrane suggest the high degree of steroidogenic activity of these cells. Apposed plasma membranes make contacts through the unique cell contacts described in the adrenocortical cells of mammals (Friend and Gilula, '72). The Golgi apparatus is described as a most conspicuous component of the cytoplasm and is presented as further evidence for the important involvement of this organelle in corticosteroidogenesis in vertebrates. These morphological observations are discussed in relation to the known secretory products of this tissue in the sturgeon, and it is suggested that there is a need for further examination of the corticosteroids produced by lower vertebrates.