Effects of thyroid function on submaxillary gland sensitivity to autonomic nervous drugs

Abstract

The effect of changes in thyroid function on the action of autonomic drugs upon the secretion of saliva by the submaxillary glands was studied in male Wistar rats. Hyperthyroidism was induced by the sc administration every 12 h of 10 micrograms/100 g bw of L-triiodothyronine; hypothyroidism was induced by surgical thyroidectomy 2 weeks before the experiments. The dose-response curves to increasing doses of isoprenaline, norepinephrine or methacholine showed in hyperthyroid animals increased salivary secretion, while in hypothyroid animals the dose-response to the drug was reduced. The threshold dose for isoprenaline was reduced in hyperthyroid animals and increased in hypothyroid ones. The threshold dose for norepinephrine did not change in hyperthyroid or hypothyroid animals while that for metacholine was decreased in hyperthyroid ones. When norepinephrine was given to alpha-blocked animals (with phentolamine) the difference in the dose-response curves between hyperthyroid and control animals was increased. But when norepinephrine was given to beta-blocked animals (with propranolol) the difference between the dose-response curves of hyperthyroid and control animals disappeared. The results above presented show that the sensitivity of the submaxillary salivary glands of rats to some adrenergic and cholinergic drugs was altered by the thyroid hormone. The effect was greater in the responses mediated by beta receptors. The structural changes in these glands may have some role in these effects.

Modulation by thyroid hormones of rat parotid amylase secretion stimulated by 5‐hydroxytryptamine

“…This is in consonance with the recently reported presence of 5-HT 4b and 5-HT 7a receptors in the rat submandibular gland (9), both receptor subtypes being coupled to the cAMP pathway (28). We showed previously that thyroid hormones modulate rat submandibular secretion that was stimulated by different agonists (19)(20)(21)(22). This fact and the well-known interaction between thyroid hormones and 5-HT cells (11)(12)(13)(14) prompted us to study the effect of thyroid status upon 5-HT-stimulated amylase secretion in parotid glands.…”

“…We showed previously that thyroid hormones modulate rat submandibular secretion that was stimulated by different agonists (19–22). This fact and the well‐known interaction between thyroid hormones and 5‐HT cells (11–14) prompted us to study the effect of thyroid status upon 5‐HT‐stimulated amylase secretion in parotid glands.…”

“…We showed previously that thyroid hormone (T 3 ) modulates rat salivary gland secretion stimulated by cholinergic and β‐adrenergic drugs (19, 20), substance P (21) or vasoactive intestinal peptide (22). In this context we investigated the modulatory action of thyroid hormones upon 5‐HT‐induced salivary secretion.…”

Effects of Exogenous Thyroid Hormone on the Postnatal Morphogenesis of the Rat Parotid Gland

“…The vacuoles that developed in the Medium and High dose T 4 pups are similar to the “watery vacuoles” described in rat parotid gland after strong secretory stimulation (Garrett,1978; Garrett et al,1978). Exogenous thyroxine has been shown to induce hypersecretion by rat salivary glands by means of adrenergic nerve (Tumilasci et al,1982; Medina et al,1984), 5‐hydroxytryptamine (Ostuni et al,2003), substance P (Tumilasci et al,1986a), and vasoactive intestinal peptide (Tumilasci et al,1986b) routes, and indirectly by increased Na+, K+ ‐dependent adenosine triphosphatase activity (Saito et al,1982). The observed appearance of vacuoles and reduction of acinar size thus are most likely due to salivary hypersecretion caused by the induced hyperthyroidism.…”

Stereological study on the submandibular gland in hypothyroid ratsNote

“…Some authors have indicated that enlarged salivary glands are common in patients with hypothyroidism but this finding is not widely appreciated (1). Most research done on these cases has focused on functional and physiological aspects of thyroid hormones on the gland (2)(3)(4)(5)(6)(7)(8) whilst there has been little work on submandibular gland morphology. The present study describes, using morphometric methods the effects of hypothyroidism on submandibular sali-vary gland structure, including acini (serous and mucous acini), major intralobular ducts (granular and striated ducts), interlobular connective tissue and excretory duct, which lie in the connective tissue (9 -12).…”