Mja. Vankempen et al., DIFFERENTIAL CONNEXIN DISTRIBUTION ACCOMMODATES CARDIAC-FUNCTION IN DIFFERENT SPECIES, Microscopy research and technique, 31(5), 1995, pp. 420-436
Using immunohistochemical staining, the distribution of connexin40 (Cx
40) and connexin43 (Cx43) was studied in rat, guinea pig, porcine, bov
ine and human hearts. These species display differences in the degree
of morphological differentiation of the conduction system. This study
was performed in the anticipation that comparison of the distributions
of Cx40 and Cx43 in young and adult specimens may provide clues as to
the physiological role of connexins in the heart. To a large extent,
the distribution patterns of Cx40 and Cx43 are comparable between spec
ies. In neonates and adults, Cx43 was immunolocalized throughout the w
orking myocardium, but in the conduction system Cx43 was detected only
after birth. Cx40 was found to appear slightly earlier in development
than Cx43 and to disappear when levels of Cx43 became more abundant.
This time course was seen in working myocardium and in the ventricular
conduction system. Together these data suggest that expression of Cx4
0 induces or facilitates expression of Cx43, while abundant expression
of Cx43 in turn leads to suppression of Cx40 expression. The exceptio
ns to this may represent blocks in this potential regulatory sequence.
A second conclusion is that Cx40 and Cx43 containing gap junctions ap
pear in the ventricular conduction system from distal to proximal and
only after birth. This indicates that terminal differentiation of the
conduction system occurs unexpectedly late in development. (C) 1995 Wi
ley-Liss, Inc.