Abstract
The comparative biological activities of intracerebroventricular (icv) injection of alpha-rat and alpha-human atrial natriuretic peptide (rANP and hANP, respectively) in the arginine vasopressin (AVP) release in conscious rats and the binding properties of these peptides to their specific receptors have been investigated. An icv injection of 5 micrograms rANP inhibited the AVP release induced by osmotic and hemorrhagic stimuli. In contrast, 20 micrograms of hANP was needed to exert an inhibitory effect on the AVP release. The receptor binding studies were carried out by using rat hypothalamic membrane preparations. The binding studies revealed that the potency of rANP was greater than that of hANP in displacing radioligand from its binding sites. Scatchard analysis revealed that the dissociation constant for rANP was significantly lower than that for hANP (0.52 +/- 0.04 vs 1.20 +/- 0.16 nM, P less than 0.01). The binding capacity of these peptides was similar. These results suggest that the greater biological potency of rANP compared with hANP in the inhibition of AVP release is caused by the difference in the binding potency of these peptides.
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