[Submaxillary glands in an endocrine context].

The evidence for interrelationships between the submandibular salivary glands (SMG) and the endocrine system is reviewed. Firstly, it has been clearly demonstrated that various hormones participate in the molecular control of exocrine enzyme synthesis in the SMG, and more particularly within the cells of the convoluted granular tubules of the gland. Testosterone was thus shown to stimulate the synthesis of a series of SMG enzymes via its specific cellular receptors and the genetic machinery of protein synthesis, while the active thyroid hormone T3, together with the glucocorticosteroids act synergistically with testosterone. In addition, experimental evidence is accumulating, ascribing to the SMG an endocrine function. More specifically, two important hormonal factors appear to originate in the SMG: the nerve growth factor (NGF), a polypeptide of 140.000 d which is highly concentrated in the SMG and plays a major role in the ontogenetic development and in the functions of spinal and sympathetic ganglia; and the epidermal growth factor (EGF), a 6.045 d peptide displaying a variety of biological actions including promotion of epidermal development, eruption of the incisors, stimulation of pituitary secretion of ACTH and GH, and inhibition of gastric and of thyroid hormone secretion. As previously observed for the SMG exocrine enzymes production, the two endocrine secretions of the SMG are also controlled by various classical hormones such as testosterone, thyroid hormones and adrenocorticosteroids. Finally, a more complex regulatory loop involving the SMG hormones was recently described, including a retrograde axonal transport of NGF from the SMG to the superior cervical ganglion (SCG) where it participates in transmitter syntheses, and, beyond the SCG, in the control of various targets of the SCG such as the pineal gland and other neuroendocrine regulations. Summing up, the buccal segment presently appears as a mixed glandular section with both exocrine and endocrine functions in the same line as the lower segments of the digestive tract, i.e. stomach, duodenum, liver and pancreas.