title: Blunted cGMP response to ANF in vascular smooth muscle cells of SHR.
abstract: Abnormalities in the coupling of atrial natriuretic factor (ANF) receptors with the guanosine 5'-cyclic monophosphate (cGMP) system in vascular smooth muscle cells (VSMCs) may play a role in the pathophysiology of hypertension in the spontaneously hypertensive rat (SHR). This concept was examined in cultured, aortic VSMCs (passages 6-10) from SHR, Wistar-Kyoto (WKY), and American Wistar (Wis) rats. Quiescent VSMCs of the SHR (serum deprived for 24 h) had higher ANF receptor density (Bmax) and lower affinity [i.e., increased equilibrium dissociation constant (Kd)] than cells from normotensive controls. Maximal binding (Bmax) (specific binding sites/cell) values for these cells were SHR 112,855 +/- 6,951, WKY 48,650 +/- 3,607, and Wis 36,122 +/- 2,607 (means +/- SE; P less than 0.001 for SHR vs. both WKY and Wis). The Kd values were (in nM) SHR 1.20 +/- 0.098, WKY 0.657 +/- 0.065, and Wis 0.37 +/- 0.037 (P less than 0.001 for SHR vs. both WKY and Wis). Despite their higher Bmax, VSMCs of the SHR showed a substantially lower maximal stimulation of cGMP accumulation in response to ANF: 987 +/- 29.3, 1,992 +/- 574.2, and 2,019 +/- 273.8 fmol.4 min-1.10(6) cells-1 for SHR, WKY, and Wis, respectively (P less than 0.01 for SHR vs. Wis and P less than 0.02 for SHR vs. WKY). Further experiments demonstrated that the poor response of SHR VSMCs to the ANF was not due to a population of receptors that did not couple to the particulate guanylate cyclase. Such findings demonstrate a dissociation of the cGMP response to ANF from the binding of the hormone to its receptors in VSMCs of the SHR compared with controls. This appears to represent a primary and innate defect in these cells that may contribute to the hypertensive process in the SHR.
authors.affiliation: Hypertension Research Center, University of Medicine and Dentistry of New Jersey, Newark 07103.
authors.forename: M
authors.initials: M
authors.lastname: Nakamura
authors.forename: A
authors.initials: A
authors.lastname: Nakamura
authors.forename: B
authors.initials: B
authors.lastname: Fine
authors.forename: A
authors.initials: A
authors.lastname: Aviv
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D006152:Cyclic GMP / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011919:Rats, Inbred Strains; D011921:Rats, Inbred WKY; D017461:Receptors, Atrial Natriuretic Factor; D011956:Receptors, Cell Surface / Q000378:metabolism
chemical_list: D011956:Receptors, Cell Surface; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor; D006152:Cyclic GMP