AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 3 704-R709, Copyright © 1996 by American Physiological Society
Adenosine A1 receptor and its gene expression in ventricles from spontaneously hypertensive rats
S. Kobayashi, S. Umemura, Y. Toya, N. Hirawa, S. Hayashi, K. Uchino and M. Ishii
Second Department of Internal Medicine, Yokohama City University, School of Medicine, Japan.
We characterized the adenosine A1 receptor and the levels of its mRNA
expression in the ventricles of 6- and 13-wk-old Wistar-Kyoto rats (WKY)
and spontaneously hypertensive rats (SHR). The binding of
2-chloro-[3H]cyclopentyladenosine ([3H]CCPA), an A1 agonist ligand, to
ventricular membranes was saturable and reversible. The receptor density
was significantly lower in SHR than in WKY at 13 wk. The dissociation
constant values were not different among these groups. In Northern blot
analysis using rat A1 receptor cDNA, levels of mRNA did not differ
significantly in the two groups at 13 wk, but the level in SHR
significantly exceeded that in WKY at 6 wk. Because plasma adenosine levels
were reported to be increased at 13 wk in SHR and we found mRNA levels were
similar at this age, the discrepancy between A1 receptor density and its
mRNA levels might be related to the desensitization of A1 receptors.
Although the implication of this decreased density of A1 receptors is not
known, it may involve an increased susceptibility to ischemia.
