Sabra rats as a model to differentiate between Na + and GTP regulation of α 2-adrenoceptor densities

Abstract

Sodium ions and guanyl nucleotides play an important role in increasing α 2-adrenoceptor densities in cerebral and renal cortex of normotensive rats. The in vitro effect of Na + and GTP was investigated on cerebral and renal α-adrenoceptors in hypertensive (SBH, salt-sensitive) and normotensive (SBN, salt-resistant) Sabra rats. In SBH and SBN rats, guanyl nucleotides increased cerebral and renal high-affinity α 2-adrenoceptor densities. Sodium ions, in contrast, markedly increased cerebral and renal high affinity α 2-adrenoceptor densities only in SBH rats. Under these conditions, α 2-adrenoceptor densities were unchanged. Thus, although Na + and GTP both increase α 2-adrenoceptor densities, these agents appear to mediate their regulatory effects via different membrane components. Moreover, the absence of sodium regulation of α 2-adrenoceptors in SBN rats may be responsible for the resistance to salt-induced hypertension.