Physiological factors affecting secretion of parotid hormone.

A parotid hormone (PH) that stimulates a dentinal fluid transport (DFT) mechanism in rat teeth is part of the hypothalamic parotid gland endocrine axis (HPEA). Infusion of a porcine hypothalamus-thalamic tissue extract (PHTE) into anesthetized rats stimulates the DFT mechanism in intact animals but is ineffective in parotidectomized rats. Infusion of PHTE into intact conscious pigs raises the plasma titer of immunoreactive PH (iPH) five- to eightfold. Parotidectomy prevents the response. The feeding of pig chow is a potent stimulus for iPH secretion: an 11-fold increase is reached within 10-20 min, and the response is directly related to the length of the feeding stimulus. No response is obtained after parotidectomy. The secretion of saliva and iPH from the parotids occurs independently of each other, suggesting different control mechanisms for each function. The immediate secretion of iPH in response to feeding and its relationship to DFT stimulation may represent a systemic physiological process by which resistance of teeth to decay is enhanced at a time when the acidogenic potential of the oral microbes is maximum.