Functional Morphology of the Teleost Pituitary Gland

Abstract

The current state of our knowledge of the morphology and histo- and cytophysiology of the teleost pituitary gland is presented. The zonation that characterizes the adenohypophysis is based on the regional distribution of specific cell types. As a result there is also a functional zonation indicated by specific hormones emanating from clearly identifiable parts of the gland. These observations make the teleost hypophysis ideal for the study of problems that may be basic to all vertebrates. The ultrastructure of hypophysial cells is presented and related to observations at the light microscope level. The manner in which secretory granules are released from specific cells is compared, and the problem of evaluating “cell activity” discussed. The application of immunohistochemical techniques to the study of the teleost pituitary gland is reviewed, and its use as a tool of investigation for future studies evaluated. These methods have helped to elucidate the cellular source of teleost pituitary hormones and have confirmed the findings of the histophysiologists.