Biomaterial Database

Individual rabbit cardiac myocytes have different thresholds for alpha myosin heavy chain regulation by thyroid hormone. 1989

Z Y Lin, and M P Wenderoth, and B R Eisenberg

Department of Physiology and Biophysics, University of Illinois College of Medicine, Chicago 60612.

Myocytes in adult rabbit ventricle express and alpha and a beta form of myosin heavy chain (MHC). The alpha-MHC distribution detected with indirect immunofluorescence has been found in different proportions in adjacent myocytes producing a mosaic staining pattern. The basis for cell-specific expression of the alpha-MHC isoform is not known. Since thyroid hormone is a major regulator of myosin gene expression, we varied the plasma thyroid level and followed the alpha-MHC content within a population of myocytes. Ventricular myocytes were induced to become 100% beta-MHC by placing the rabbits on a 0.15% propylthiouracil diet for 70 days. L-triiodothyronine (LT3) over a dose range of 1 to 10 micrograms/kg/day was delivered by an osmotic minipump for 5 days, with actual serum levels confirmed by LT3 radioimmunoassay to be in the range of from 115 to 1,230 ng/dl. The amount of alpha-MHC that returned was estimated in randomly selected cells by measuring the relative intensity of the fluorescence-tagged secondary antibody. The normal mosaic pattern of alpha-MHC expression in the left ventricle returned with an LT3 dose of 2-5 micrograms/kg/day. The first myocytes to express alpha-MHC were in the subepicardium and did so at a LT3 serum level of 115 of ng/dl. All myocytes of the ventricular wall expressed alpha-MHC at serum levels above 1,230 ng/dl. These data are interpreted to show that the variation of myosin isoform content seen in the adult heart is indicative of heterogeneity of thyroid sensitivity, with the threshold for serum LT3 being between 115 and 370 ng/dl.

UI	MeSH Term	Description	Entries
D009206	Myocardium	The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.	Muscle, Cardiac,Muscle, Heart,Cardiac Muscle,Myocardia,Cardiac Muscles,Heart Muscle,Heart Muscles,Muscles, Cardiac,Muscles, Heart
D009218	Myosins	A diverse superfamily of proteins that function as translocating proteins. They share the common characteristics of being able to bind ACTINS and hydrolyze MgATP. Myosins generally consist of heavy chains which are involved in locomotion, and light chains which are involved in regulation. Within the structure of myosin heavy chain are three domains: the head, the neck and the tail. The head region of the heavy chain contains the actin binding domain and MgATPase domain which provides energy for locomotion. The neck region is involved in binding the light-chains. The tail region provides the anchoring point that maintains the position of the heavy chain. The superfamily of myosins is organized into structural classes based upon the type and arrangement of the subunits they contain.	Myosin ATPase,ATPase, Actin-Activated,ATPase, Actomyosin,ATPase, Myosin,Actin-Activated ATPase,Actomyosin ATPase,Actomyosin Adenosinetriphosphatase,Adenosine Triphosphatase, Myosin,Adenosinetriphosphatase, Actomyosin,Adenosinetriphosphatase, Myosin,Myosin,Myosin Adenosinetriphosphatase,ATPase, Actin Activated,Actin Activated ATPase,Myosin Adenosine Triphosphatase
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D005260	Female		Females
D005786	Gene Expression Regulation	Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.	Gene Action Regulation,Regulation of Gene Expression,Expression Regulation, Gene,Regulation, Gene Action,Regulation, Gene Expression
D006321	Heart	The hollow, muscular organ that maintains the circulation of the blood.	Hearts
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013961	Thyroid Gland	A highly vascularized endocrine gland consisting of two lobes joined by a thin band of tissue with one lobe on each side of the TRACHEA. It secretes THYROID HORMONES from the follicular cells and CALCITONIN from the parafollicular cells thereby regulating METABOLISM and CALCIUM level in blood, respectively.	Thyroid,Gland, Thyroid,Glands, Thyroid,Thyroid Glands,Thyroids
D014284	Triiodothyronine	A T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5' position of the outer ring of the iodothyronine nucleus. The hormone finally delivered and used by the tissues is mainly T3.	Liothyronine,T3 Thyroid Hormone,3,3',5-Triiodothyronine,Cytomel,Liothyronine Sodium,Thyroid Hormone, T3