Beta-adrenoceptors in the rat parotid gland enlarged by salivariectomy and bulk diet. Effects of denervation.

The numbers of beta-adrenergic receptors and level of cyclic AMP (cAMP) of the parotid gland of adult female rats were determined 4 weeks after introduction of a regimen that induced a 2-fold increase in gland weight. This regimen consisted of ablation of the submandibular-sublingual glands and substitution of the normal chow diet with a bulk diet consisting of 50% inert cellulose and 50% ground solid chow. There was a 2.4-fold increase in number (density) of beta-adrenoceptors in the enlarged parotid gland when comparison was made with parotid glands of control rats. The beta-adrenoceptor present in the enlarged and normal glands was of the beta 1 subtype. Removal of either autonomic pathway at the time of partial salivariectomy and dietary substitution was followed by a small reduction in number of beta-adrenoceptors (4-9% with either denervation), but when both nerves were removed the reduction was 25%; in magnitude, these changes were generally similar to those observed with denervated parotid glands of chow-fed rats. The norepinephrine concentration of the enlarged gland was much less than that of normal glands (reduced 38%); sympathectomy of normal or enlarged parotid glands resulted in a marked lowering of norepinephrine concentrations (to 1-5% of control levels); parasympathectomy had no effect on norepinephrine concentration of enlarged parotid glands but caused a decrease in that of the parotid of normal size. Apparently, the number of beta-adrenoceptors depends on the degree of activity of both the parasympathetic and sympathetic nerves to the parotid.(ABSTRACT TRUNCATED AT 250 WORDS)