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

Abstract

The effects of 5-hydroxytryptamine (5-HT) upon amylase secretion by rat parotid glands were studied in three groups of animals: (a) intact control rats (euthyroid rats); (b) hypothyroid rats obtained by surgical thyroidectomy 2 wk before the experiments; and (c) hyperthyroid rats obtained by the administration of sodium l-triiodothyronine for 2 wk before the experiments. Hyperthyroid rats showed significantly higher baseline amylase release than control rats. When the glands were stimulated with 5-HT (30 micro m), amylase release was significantly lower in the hypothyroid group and higher in the hyperthyroid rats than in control group. Addition of cholinergic, adrenergic or substance P antagonists did not modify 5-HT-stimulated amylase activity. The effects of 5-HT were partly but significantly blocked by the addition of 10 micro m methysergide (HT1/2/7 receptor blocker) in the three groups of rats. In contrast, 10 micro m ketanserine (HT2A receptor blocker) partly blocked the response to 5-HT only in the hyperthyroid animals. It was concluded that 5-HT induces amylase secretion by rat parotid glands through specific serotoninergic receptors, and that thyroid status modulates the 5-HT effect.

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.…”

Comparative study of the effect of experimentally induced hyperthyroidism and hypothyroidism on the parotid gland in adult male albino rats

“…There are problems in eating, speaking, and swallowing and frequent disturbances in taste perception [8,19] . 5-HT-induced amylase secretion in rat's parotid gland was modulated by thyroid status [22] . Many studies have correlated between salivary gland dysfunction and autoimmune thyroiditis [7] .…”

Intraluminal volume homeostasis

“…In mammals like humans they also secrete digestive enzymes such as amylases. 19 Immunohistochemical analysis of rat submaxillary salivary glands showed the presence of 5-HT in the epithelial cells of excretory ducts and acini. 20 The same cells that were positive for 5-HT were also found to contain basolateral membrane of mouse and human mammary epithelial cells 8,9 as depicted in the model in Figure 1.…”