Atrial natriuretic factor stimulates Na/K/Cl cotransport in vascular smooth muscle cells.

Abstract

Atrial natriuretic factor (ANF) is a collective term used to describe a group of peptides isolated from mammalian atria which have vasorelaxant activity as well as diuretic and natriuretic activity. Recently, ANF peptides have been shown to bind to specific receptors on vascular smooth muscle cells (VSMC) and to cause an elevation in cGMP levels.We have previously demonstrated that VSMC possess a prominent, cyclic-nucleotide-sensitive Na/K/Cl cotransport system. In the present study, the effects of the ANF peptide rat atriopeptin III (rAP III) were measured on Na/K/Cl cotransport of VSMC by using primary cultures derived from rat thoracic aorta. It was found that rAP HI caused a marked elevation of Na/K/Cl cotransport. Maximal stimulation occurred at 100 nM, and the dose of rAP III required for half-maximal potassium influx (Kl,2) was 9 nM. We also investigated the effect of rAP m on cGMP levels in VSMC. It was found that rAP III increased cGMP in a dose-dependent manner, with a K/,2 value of 10 nM. Finally, we measured the effect of the permeable cGMP analog 8-bromo-cGMP on Na/K/Cl cotransport. It was found that 8-bromo-cGMP stimulated cotransport to the same extent as did a saturating dose of rAP HI (Ky,2 = 0.2 ,AM). Saturating doses of rAP HI and 8-Br-cGMP in combination did not stimulate cotransport in an additive manner, suggesting that rAP III probably does not elevate cGMP via inhibition of phosphodiesterase. These findings suggest that activation of Na/K/Cl cotransport via elevations in cGMP may be associated with ANF-mediated vasorelaxation and/or ANF-mediated diuresis and natriuresis.

Modulation of rabbit ventricular cell volume and Na+/K+/2Cl- cotransport by cGMP and atrial natriuretic factor.

“…Once Na+/K+/2C1-cotransport is fully inhibited by BUM, agents that act solely by inhibiting the same transporter should be ineffective. The EDs0 for reduction of cell volume by 8-Br-cGMP, ~0.8 ~M, is comparable to the 8-Br-cGMP sensitivity of Na+/K+/2C1-cotransport in other tissues (O'Donnell and Owen, 1986;O'Donnell, 1989).…”

“…Correspondingly, after M&B22948 treatment, a threshold dose of ANF gave rise to a maximally effective increase in cGMP. M&B22948 also potentiates ANF's vasodilatory and natriuretic effects in rats and rabbits (Weishaar et al, 1990) and its stimulation of Na+/K+/2CI-cotransport in vascular smooth muscle (O'Donnell and Owen, 1986). Fifth, pretreatment with a maximally effective dose of 8-Br-cGMP eliminated the ability of ANF to decrease cell volume.…”

“…1) and suggest that cGMP, like ANF (Clemo and Baumgarten, 1991a), reduces cell volume by inhibiting Na+/K+/ 2C1-cotransport. Because ANF increases cytosolic cGMP levels in heart by stimulating guanylate cyclase (Cramb et al, 1987;Anand-Srivastava et al, 1989;Rugg et al, 1989) and ANF modulates Na+/K+/2CI-cotransport in other tissues via cGMP (O'Grady et al, 1985;O'Donnell and Owen, 1986;O'Donnell, 1989), it is appealing to postulate that cGMP is the second messenger for ANF-induced cardiac cell shrinkage.…”

“…ANF stimulates Na+/K+/2CI -cotransport in rat aortic vascular smooth muscle (O'Donnell and Owen, 1986), but inhibits the cotransporter in flounder intestinal epithelium (O'Grady, Field, Nash, and Rao, 1985) and cultured bovine aortic endothelial cells (O'Donnell, 1989). Both the inhibition and stimulation of Na+/K+/2C1 -cotransport in these systems is attributed to an ANF-induced increase in the cytosolic level of guanosine 3',5'-monophosphate (cGMP).…”

Role of cyclic GMP in atrial‐natriuretic‐peptide stimulation of erythrocyte Na+/H+ exchange

“…Tyr at the carboxy terminus has been shown not to reduce the potencies of ANP fragments in the stimulation of intracellular cGMP production (Budzik et al, 1987;Scarborough et al, 1986), of vasodilation and of natriuresis (Katsube et al, 1985). Truncation of Phe-Arg-Tyr at the carboxy terminus has, however, been shown to reduce the potencies of the stimulation of cGMP production in cells (Leitman et al, 1986;Scarborough et al, 1986), of vasodilation (Katsube et al, 1985;O'Donnell et al, 1987;Owen et al, 1987), of diuresis and of natriuresis (Katsube et al, 1985) and also the potency of the regulation of cellular Na+/K+ cotransport O'Grady et al, 1985;Owen et al, 1987). Deletion of Ser-Ser at the amino terminus also reduced the potencies of ANP peptides to stimulate vasorelax-ation Owen et al, 1987) and to act on cellular Na+/K+ cotransport O'Grady et al, 1985;Owen et al, 1987).…”