According to salivary gland endocrine theory the hormone like substance, known as parotin and extracted from the parotid gland, is biologically active in lowering the serum calcium level and promoting calcification of the teeth and bones. The parotid gland extract is also known to activate anterior pituitary function and eleborates an antagonistic action to the parathyroid gland extract and thyroid gland. Recent studies, however, suggest that calcium homeostasis is mainly regulated by two endocrine hormones, that is, parathormone of the parathyroid gland and calcitonin of the ultimobranchial gland. The promotion or inhibition of their secretions is determined by the level of calcium in circulation. There was no evidence that the anterior pituitary gland or other parts of the central nervous system had any direct effect on their secretions.
Recent study suggested that adrenal cortical steroid, which was known to influence bone growth and calcium metabolism, could inhibit the action of both parathormone and calcitonin. Other studies on the regulation of salivary secretion reported that the diencephalon, especially hypothalamus served as an integrate area of salivation and there was a positive correlation between the salivary flow and calcium concentration of the saliva and serum.
The author, hereby, made an experimental study to find out the sites of the central nervous system in which might exert central regulatory effect on calcium metabolise: through the parotid gland extract. The Korean :-:hite male rabbits weighing 1.8 kg were used for this study. Before experiment no meals were given for at least 24 hours. Normal physiological saline was employed for the control study. The purified parotid gland extract, parotin, was at first injected intravenousely (1 mglkg and 2 mg/kg, respectively) and then into various areas of the central nervous system e.g. pre-optic area, anterior hypothalamus, posterior hypothalamus, mid-hypothalamus, median eminence, mammillary body, hippocampus, caudate nucleus, amygdala, putamen, midbrain and salivary nucleus by using stereotaxic apparatus in amount of 0.05 ml. (0.25 mgt bilaterally. Serum calcium was estimated with atomic absorption spectrophotometer.
The results were summarized as fcilows
1. The serum calcium was decreased i0-14.% by intravenous injection r- the parotid gland extract.
2. A marked decrease of serum calcium was observed by injection of the parotid gland extract
into the pre-optic area (14%´ reduction rate) and anterior hypothalamus (16% reduction rate.)
3. A slight but insignificant decrease of serum calcium was observed by injection of the parotid gland extract into the posterior hypothalamus (8916 raductor rate), mammillary body (9%) and hippocampus (8%)
4. No noticeable change of serum calcium was observed by injection of the parotid gland extract into the mid-hypothalamus, median eminence, caudate nucleus, amygdala, putamen, mid-brain and salivary nucleus.
With the results of the above the author could conclude that the anterior hypothalamus and the pre-optic area might be the central regulatory sites of calcium metabolism through the action of parotid gland extract.
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