AJP - Heart and Circulatory Physiology, Vol 272, Issue 6 2639-H2644, Copyright © 1997 by American Physiological Society
Upregulation of expression of sarcoplasmic reticulum by TGF-beta 1 in cultured rat cardiac myocytes
H. Kimura, H. Takemura, K. Imoto, H. Ohshika and Y. Mochizuki
Department of Pharmacology, School of Medicine, Sapporo Medical University, Japan.
The effects of transforming growth factor-beta 1 (TGF-beta 1) on the
function and structure of sarcoplasmic reticulum (SR) were studied in
cultured neonatal rat cardiac myocytes. The cardiac myocytes at days 2 and
6 of culture exhibited spontaneous contraction; however, the rate of
contraction increased and became regular, depending on culture day.
Ryanodine and norepinephrine (NE) increased the rate of contraction and
frequency of Ca2+ oscillations in myocytes at day 2 of culture. Ryanodine
did not affect the spontaneous contraction in nontreated and TGF-beta
1-treated myocytes. On the other hand, NE caused negative and positive
chronotropic responses in nontreated and TGF-beta 1-treated cells,
respectively. In the absence of extracellular Ca2+, ryanodine and NE did
not affect the cytoplasmic Ca2+ concentration ([Ca2+]i) in the nontreated
cells, whereas NE increased [Ca2+]i but ryanodine did not in the TGF-beta
1-treated cells. SR structures in TGF-beta 1-treated cells developed more
than those in nontreated cells. The results indicate that TGF-beta 1 plays
an important role in the upregulation of SR function and structure of
cultured neonatal rat cardiac myocytes.
