Enhancement of intracellular sodium by vasopressin in spontaneously hypertensive rats.

Abstract

The arginine vasopressin-induced increase in intracellular sodium concentration was augmented in cultured rat vascular smooth muscle cells derived from 12-week-old spontaneously hypertensive rats (SHR) compared with those from 12-week-old normotensive Wistar-Kyoto (WKY) rats. This difference was enhanced by treatment with a Na + ,K + -ATPase inhibitor, ouabain. The calcium-free state did not affect the basal intracellular sodium concentration but completely blocked the arginine vasopressininduced increase in intracellular sodium concentration in both cell groups. The arginine vasopressinmobilized cytosolic free calcium was enhanced in SHR compared with WKY rats. This enhancement was diminished but not completely inhibited in the calcium-free state. Also, arginine vasopressin-produced intracellular alkalinization was augmented in SHR. Pretreatment of both cell groups with a calmodulin antagonist, JV-(6-aminohexyl)-5-chloro-l-naphthalenesulfonamide, completely blocked arginine vasopressin-induced intracellular alkalinization and increased intracellular sodium concentration. Scatchard analysis showed that the V t receptor number of either quiescent or proliferative cells of SHR was five to seven times greater than that of WKY rats, without any change in receptor affinity. These findings therefore indicate that the arginine vasopressin-induced increase in intracellular sodium concentration is augmented in vascular smooth muscle cells of SHR mediated through the enhancement of the mobilization of cytosolic free calcium and the activity of sodium-hydrogen exchange, which depends on an increase in V, receptor number. (Hypertension. 1993;22:300-305 The present study therefore was undertaken to determine whether there is any difference in the AVPinduced increase in [Na + ]| between VSMCs of SHR and WKY rats by the direct measurement of [Na + ]i with a fluorescence indicator dye, sodium-binding benzofuran isophthalate (SBFI). We also examined an AVP V, receptor analysis and the measurement of [Ca 2+ ] ( mobilization, as well as changes in intracellular pH (pHj), in response to AVP in VSMCs of both rat strains to explore the cellular mechanism. Methods Cell CultureRat VSMCs derived from SHR and WKY rats were isolated using the modified method of Chamley et al. 912 Briefly, rat thoracic aortas were dissected from eight SHR and WKY rats (12 weeks old) (Charles River Japan Inc, Kanagawa, Japan) and then incubated in Eagle's minimum essential medium (MEM) (ICN/Flow Laboratories Inc, Costa Mesa, Calif) containing 2 mg/mL collagenase (Worthington Biochemical Corp, Freehold, NJ) for 1 hour at 37°C. After the removal of adventitia and small fragments of the outer membrane, the aortas were minced and incubated in Eagle's MEM containing 2 mg/mL collagenase for 2 hours at 37°C. The freshly isolated cells were resuspended in Eagle's MEM containing 1 /xmol/L L-glutamine, 100 U/mL penicillin, 137 jtmol/L streptomycin, and 10% fetal bovine serum (FBS), pH 7.4. The cells were kept in a humidified incubator at 37°C with 95% air and ...

Alterations of Renal Vasopressin V_1A and V₂ Receptors in Spontaneously Hypertensive Rats

“…In the present study, plasma AVP levels increased significantly in young SHR during the development of hypertension which agrees with results in the previously cited reports. In vivo and in vitro studies revealed that enhanced responsiveness to AVP via the V 1A and V 2 receptors also occurs in severel hypertension model systems [13,14,28,29]. Jeffries et al [14] reported that AVP plays an important role in sodium retention governed by V 2 receptors in deoxycorticosterone acetate/ salt induced hypertension in rats and suggested that exaggerated V 2 receptor mediated responses in the distal cortical nephron may play an important role in the pathogenesis of hypertension.…”

Efficient gene transfer of a simian immuno‐deficiency viral vector into cardiomyocytes derived from primate embryonic stem cells

“…Intracellular calcium transience of the EBs and rat neonatal cardiomyocytes was measured as described previously 16. Briefly, cells were loaded with fura‐2‐AM (Dojin Biochemicals, Kumamoto, Japan), washed and transferred to the chamber of a fluorescence spectrophotometer (CAF‐100; Japan Spectroscopic Co., Tokyo, Japan).…”

Upregulation of V1receptors in renal resistance vessels of rats developing genetic hypertension

“…Several binding studies provide support for the view that the Okamoto-Aoki strain difference in vascular reactivity is due to greater V 1 receptor number, without any change in receptor affinity. In one study, the density of AVP receptors was found to be five times greater in cultured thoracic aortic smooth muscle cells of 12-wk-old SHR, either in proliferative or quiescent states, compared with those from WKY (34). In a recent study on freshly isolated smooth muscles cells from preglomerular vessels, we observed a more pronounced increase in cytosolic calcium after AVP stimulation in 7-wk-old SHR compared with WKY (20).…”