H. Dalen et al., EFFECT OF COLLAGENASE ON SURFACE EXPRESSION OF IMMUNOREACTIVE FIBRONECTIN AND LAMININ IN FRESHLY ISOLATED CARDIAC MYOCYTES, Journal of Molecular and Cellular Cardiology, 30(5), 1998, pp. 947-955
The extracellular glycoproteins fibronectin (FN) and laminin (LMN) are
ubiquitously expressed in myocardial tissue. These glycoproteins are
important for cellular attachment and differentiation of the cardiac m
yocytes. Utilizing specific antibodies for the detection of FN and LMN
, respectively, the distribution of these extracellular proteins was e
xamined in enzymatically isolated adult cardiac myocytes. Immunofluore
scence staining of rod-shaped cardiac myocytes revealed only remnants
of immunoreactive FN on the cellular surface and in the transverse tub
ular membrane system. LMN expression, however, was preserved in a rast
er-like pattern in the cardiac myocytes. In order to study the distrib
ution of these glycoproteins at high resolution, scanning electron mic
roscopy using the backscattered electron mode was combined with immuno
gold staining and silver-enhancement. In addition, to confirm the immu
nofluorescence microscopic observations it was shown that FN labelling
was restricted to ill-defined extracellular material and that LMN was
absent from the intercalated discs of the cardiac myocytes. The hyper
contracted cells were characterized by numerous surface protrusions de
void of immunoreactive LMN. Thus, these results indicate that FN and L
MN are differently affected by collagenase treatment, and that these c
hanges of glycoprotein expression may influence the normal function of
the cardiac myocytes as well as the membrane stability during the dev
elopment of irreversible cellular lesions. (C) 1998 Academic Press Lim
ited.