ATRIOPEPTIN REGULATION AND RENAL-FUNCTION IN CONSCIOUS SPONTANEOUSLY HYPERTENSIVE RATS

We examined the interaction of a non-guanylate cyclase-linked atriopeptin (AP) binding site ligand, SC-46542 (des[Phe106, Gly107, Ala115, Gln116]AP-(103-126)), and an endopeptidase 24.11 inhibitor, thiorphan, on mean arterial pressure, urinary sodium excretion, urinary cyclic guanosine monophosphate (cGMP) excretion, plasma cGMP concentration, and plasma AP immunoreactivity (ir) in conscious spontaneously hypertensive rats (SHR) and normo-tensive Wistar-Kyoto rats (WKY). Compared to vehicle control rats, coadministration of SC-46542 and thiorphan increased urinary sodium excretion in SHR from 2.1 ± 0.3 to 11.6 ± 0.7 μEq/min/100 g body weight and in WKY from 1.6 ± 0.4 to 4.4 ± 0.4 μEq/min/100 g body weight, and increased urinary cGMP excretion in SHR from 2.7 ± 0.5 to 79.0 ± 17.5 pmol/min/100 g body weight and in WKY from 7.0 ± 3.0 to 72.4 ± 10.6 pmol/min/100 g body weight. The change in urinary sodium excretion was greater in SHR than WKY. The coadministration of SC-46542 and thiorphan had greater effects on urinary sodium excretion and urinary cGMP excretion than administration of either compound alone. Coadministration of thiorphan and SC-46542 had no effect on glomerular filtration rate or plasma cGMP concentration, suggesting that the urinary cGMP excretion response was nephrogenous. Compared to vehicle control rats, plasma APir was increased during coadministration of SC-46542 and thiorphan in both SHR (998 ±76 ν 5.10 ± 116 pg/mL) and WKY (775 ± 36 v 414 ± 36 pg/mL). Mean arterial pressure was unaffected by SC-46542 and thiorphan in SHR or WKY. These results indicate that SC-46542 and thiorphan interact within the kidney to increase urinary sodium and cGMP excretion in conscious SHR and WKY. © 1990 by the American Journal of Hypertension, Ltd.