now this seems explainable
MikeS said:
The protein systhesis in heart muscle certainly is not for hypertrophy, as it is in skeletal muscles-in which the action is accelerated by androgen receptors
and testosterone. The smooth muscle and heart muscle were not designed for hypertrophy in the way skeletal (type II) muscles are.
then how does the heart grow? Guess u have to analyze the growth process of muscle and then see if it associates with growth in different types of muscle tissue. The obvious culprit for any tissue anabolism is IGF-1 this is the final product that stimulates growth in tissues.
Androgen Receptors Mediate Hypertrophy in Cardiac Myocytes
James D. Marsh, MD; Michael H. Lehmann, MD; Rebecca H. Ritchie, PhD; Judith K. Gwathmey, VMD, PhD; Glenn E. Green, MD; ; Rick J. Schiebinger, MD
From the Program in Molecular and Cellular Cardiology, Departments of Medicine and Otolaryngology, Harper Hospital, Detroit, Mich; the VA Medical Center, Boston University Medical Center, Boston, Mass (J.K.G.); and the Arrhythmia Center/Sinai Hospital (M.H.L.) and Wayne State University School of Medicine, Detroit, Mich (J.D.M.).
Correspondence to James D. Marsh, MD, Wayne State University School of Medicine, 421 E Canfield Ave, Detroit, MI 48201. E-mail
[email protected]
Abstract
Background—The role of androgens in producing cardiac hypertrophy by direct action on cardiac myocytes is uncertain. Accordingly, we tested the hypothesis that cardiac myocytes in adult men and women express an androgen receptor gene and that myocytes respond to androgens by a hypertrophic response.
Methods and Results—We used reverse transcription–polymerase chain reaction methods to demonstrate androgen receptor transcripts in multiple tissues and [3H]phenylalanine incorporation and atrial natriuretic peptide secretion as markers of hypertrophy in cultured rat myocytes. Messenger RNA encoding androgen receptors was detected in myocytes of male and female adult rats, neonatal rat myocytes, rat heart, dog heart, and infant and adult human heart. Both testosterone and dihydrotestosterone produced a robust receptor-specific hypertrophic response in myocytes, determined by indices of protein synthesis and atrial natriuretic peptide secretion.
Conclusions—
Androgen receptors are present in cardiac myocytes from multiple species, including normal men and women, in a context that permits androgens to modulate the cardiac phenotype and produce hypertrophy by direct, receptor-specific mechanisms. There are clinical implications for therapeutic or illicit use of androgens in humans.
found this one too
Immunohistochemical localization of androgen receptors with mono- and polyclonal antibodies to androgen receptor
H Takeda, G Chodak, S Mutchnik, T Nakamoto, and C Chang
Rat, human, and mouse tissues were stained immunohistochemically using mono- and polyclonal androgen receptor antibodies. Monoclonal antibodies were raised in rats and used to stain human and mouse tissues; polyclonal antibodies were raised in rabbits and used to stain rat tissues. Frozen tissue sections were incubated with the appropriate androgen receptor antibody and staining was completed by the indirect avidin-biotin peroxidase method. A comprehensive survey of rat and mouse tissues was performed. Antibody staining was found exclusively in the nucleus of certain specific cell types, suggesting that the androgen receptor is a nuclear protein. All male sexual organs in the rat showed strong positive nuclear staining for androgen receptor. Weaker positive reactions were seen in kidney, liver, adrenal cortex and pituitary gland.
Furthermore, positive staining for androgen receptor was exhibited in skeletal, cardiac and smooth muscle cells, and central nervous tissue. Female reproductive organs also contained androgen receptor-positive cells. The spleen was found to be the only organ examined which did not stain for androgen receptor. The monoclonal antibody could also demonstrate androgen receptor-positive cells in a human prostatic cancer and in a prostate with benign hyperplasia. These data demonstrate the use of antibodies in revealing cellular/subcellular distribution of androgen receptor in target tissues.
.gif "IP Gear")
