title: Circadian rhythm of the thyroid mast cells in untreated and methylthiouracil-treated rats.
abstract: Recent investigation have shown that mast cells of the rat thyroid participate in the regulation of thyroid function. Serotonin released from the mast cells influenced by thyrotropin promotes iodothyronine secretion by its effect on the thyroid follicle cells. The present histophysiological studies on the circadian rhythm in the normal rat thyroid reveal a close correlation between the number of the thyroid mast cells and the thyroid function. It has been shown that in the morning, when thyroid function is decreased, the number of the mast cells is low, but at noon it shows an increase an then is highest in the evening, when the thyroid activity is most intense. This phenomenon suggests a relationship between the mast cell function and the thyroid feedback mechanism. In methylthiouracil-treated rats inhibition of the thyroid iodothyronine production and change of the feedback mechanism function induce development of a hypertrophic goitre in which degranulation of the mast cells accompanied by release of their bioamines induce dilatation of blood vessels and increase in the thyroid blood flow. Simultaneously the circadian rhythm of the thyroid mast cell occurrence is changed, i.e. their number found in the morning gradually decreases by the evening.
authors.forename: G
authors.initials: G
authors.lastname: Mödlinger
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008407:Mast Cells / Q000187:drug effects* / Q000502:physiology; D008779:Methylthiouracil / Q000494:pharmacology*; D051381:Rats; D013961:Thyroid Gland / Q000166:cytology* / Q000187:drug effects
chemical_list: D008779:Methylthiouracil