Sex difference of functional and structural alterations in the myocardium of rats with hypothyroidism

• Published in: Fiziolohichnyi zhurnal (Kiev, Ukraine : 1994) Ukraine : 1994), 2013, Vol.59 (2), p.18-22
• Main Authors: Khara, M R, Pavlovych, S I, Mykhaĭliuk, V M
• Format: Article
• Language: Ukrainian
• Subjects: Acetylcholine - metabolism; Acetylcholine - pharmacology; Animals; Bradycardia - metabolism; Bradycardia - pathology; Bradycardia - physiopathology; Disease Models, Animal; Female; Heart Ventricles - drug effects; Heart Ventricles - innervation; Heart Ventricles - pathology; Heart Ventricles - physiopathology; Hypothyroidism - metabolism; Hypothyroidism - pathology; Hypothyroidism - physiopathology; Male; Methimazole - pharmacology; Myocardium - metabolism; Myocardium - pathology; Myocytes, Cardiac - metabolism; Myocytes, Cardiac - pathology; Orchiectomy; Ovariectomy; Rats; Receptors, Cholinergic - metabolism; Sex Characteristics; Sinoatrial Node - drug effects; Sinoatrial Node - metabolism; Sinoatrial Node - physiopathology; Vagus Nerve - physiopathology; Vagus Nerve Stimulation; Ventricular Function - drug effects; Ventricular Function - physiology
• ISSN: 2522-9028

In experiments on sexually mature rats we studied specific cholinergic regulations of the heart and the degree of its structural damage in hypothyroidism, depending on gender and hormone-productive activity of the gonads. Hypothyroidism in sexually mature males and females was modelled with mercazolil intragastric administration (75 mg/kg) daily during 15 days. We also studied the intensity of bradycardia, which occurred in response to electrical stimulation of vagus nerve and intravenous acetylcholine administration. The degree of structural heart damage was assessed by the percentage of damaged cardiomyocytes in the ventricles of myocardium. It was found that one of the mechanisms of bradycardia in merkazolil-induced hypothyroidism is an increase of the sensitivity of sinus node cholinergic receptors and release of more quanta of acetylcholine from stimulated nerves vagus endings, what was more intense in females. The intensity of bradycardia in hypothyroidism was more significant in gonadectomized animals than in individuals with preserved gonads. The mechanisms of its occurrence in males consist of release of greater amount of acetylcholine from the endings of the nerves vagus, and in females it was the result of significant increase of the sensitivity of sinus node cholinergic receptors. Regardless of the gonads activity, structural damage of the myocardium in merkazolil-induced hypothyroidism was more intensive in female rats.