The hypoxia-induced effects on the binding sites and affinity constant of adrenoceptors, in the presence and absence of phentolamine, were determined for atrial membranes of hearts from normal and genetically hyperlipidaemic Yoshida (YOS) rats. Atrial function was also measured during normoxia and hypoxia, in the presence and absence of phentolamine. Hypoxia increased a1-adrenoceptor density in atrial membranes of normal rats (Bmax 10.6 to 26.7 fmoles/mg protein). Phentolamine prevented the increase in the Bmax of α1-adrenoceptors and increased the equilibrium dissociation constant of these receptors (KD 0.17 to 0.53 nmol/l). Beta-adrenoceptors did not change during hypoxia, but the Bmax was slightly increased (26%) in the presence of phentolamine. Thus, the α1/\ ratio increased from 0.40 in normoxia to 1.06 in hypoxia. In normoxic atria from YOS rats, the α1/\ ratio was already elevated (0.86) in comparison to control rats (mainly due to a higher density of at-adrenoceptors in atrial ...
Phentolamine and Hypoxia: modulation of contractility and alpha1-adrenoceptors in isolated atria
FROLDI, Guglielmina;RAGAZZI, Eugenio;CAPARROTTA, Laura;BOREA, Pier Andrea;
1994
Abstract
The hypoxia-induced effects on the binding sites and affinity constant of adrenoceptors, in the presence and absence of phentolamine, were determined for atrial membranes of hearts from normal and genetically hyperlipidaemic Yoshida (YOS) rats. Atrial function was also measured during normoxia and hypoxia, in the presence and absence of phentolamine. Hypoxia increased a1-adrenoceptor density in atrial membranes of normal rats (Bmax 10.6 to 26.7 fmoles/mg protein). Phentolamine prevented the increase in the Bmax of α1-adrenoceptors and increased the equilibrium dissociation constant of these receptors (KD 0.17 to 0.53 nmol/l). Beta-adrenoceptors did not change during hypoxia, but the Bmax was slightly increased (26%) in the presence of phentolamine. Thus, the α1/\ ratio increased from 0.40 in normoxia to 1.06 in hypoxia. In normoxic atria from YOS rats, the α1/\ ratio was already elevated (0.86) in comparison to control rats (mainly due to a higher density of at-adrenoceptors in atrial ...I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
