| Objective: To determine whether expression of water channel-2 (aquaporin 2, AQP2) in the kidney tissue differs between spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) and the effect of AVP and benazepril on the expression of AQP2. Methods: 24 male spontaneously hypertensive rats, aged 12 wks, weighed 200-300 g, were randomly divided into 3 groups: benazepril (SHRben), AVP (SHRavp)andsaline were given only in SHRctrl . 8 age and gender matched WKY served as controls.After 8 weeks' administration, the rats were decollated, and plasma concentration of AVP was measured with radioimmunoassay. Plasma osmolalities were measured with freezing point osmometer. Kidney tissue samples (lOOmg) of rats in each group were used , and the expression levels of AQP2 mRNA and AQP2 protein were determined with RT- PCR and immunohistochemistry . All data were expressed as mean+/- SD.Result: There was no difference of initial blood pressure of SHR before treatment, but was significantly higher than that of WKY (mmHg, 167 15 vs 115 12, 171 13 vs 115 12, 173 14 vs 115 12, P < 0. 05) . After 8 weeks' administration of benazepril, the blood pressure of SHRbenwas significantly lower than that ofSHRctri. (112 17vsl69 9 mmHg,P < 0. 05). After 5 days' injection of vasopressin, the blood pressure of SHRavp is not higher than that of SHRctrl (172 15vs 169 9mmHg, P > 0. 05) . When SHRctrl compared with WKY, levels of AQP2 mRNA(0. 72 0. 17 vs 0. 36 0. 13, p<0. 05)and AQP2 protein expression(0. 62 0. 12 vs 0. 45 0. 15, p<0. 05), concentrations of AVP(87. 16 + 8. 2 vs 60.8 + 4.45 pg/ml,p<0. 05) as well as plasma osmolalities (303 + 9 vs 292 + 7 mosm, p<0. 05) were significantly higher .When SHRbencompared withSHRctr], levels of AQP2 mRNA (0.48 0.11 vs 0. 72 0. 17,P<0. 05) and AQP2 protein expression (0. 47 0. 09 vs 0. 62 0. 12, P<0. 05) , concentrations of AVP (61. 79 9. 19 vs 87. 16 + 8. 2 pg/ml, P<0. 05) as well as plasma osmolalities (293 + 9 vs 303 9 mosm, P<0. 05) was significantlydecreased. When SHRavp compared with WKY, levels of AQP2 mRNA (0. 76 0. 15 vs 0. 36 0. 13,P<0. 05) , AQP2 protein expression (0. 71 0. 13 vs 0. 45 0. 15, P<0. 05) .concentrations of AVP (89 + 5.48 vs 60.8 + 4.45 pg/ml, P<0. 05) as well as plasma osmolalities (309 +llvs292 +7 mosm, P<0. 05) increased, and compared withSHRhcn, Levels of AQP2 mRNA (0. 76 0. 15 vs 0. 48 + 0. 11, P<0. 05) , AQP2 protein expression (0. 71 + 0. 13 vs 0. 47 0. 09, P<0. 05) , concentrations of AVP (89 + 5.48 vs 61. 79 + 9. 19 pg/ml, P<0. 05 ) as well as plasma osmolalities (309 11 vs 293 9 mosm, P<0. 05 ) is also higher. All the above parameters show no differenceas SHR),en compared with WKY, SHRavp compared with SHRctr|.Conclusions: Expression levels of AQP2 mRNA and AQP2 protein in kidney tissue of SHR were up-regulated, which may play a certain role in the development and maintenance of hypertension in spontaneously hypertensive rats, benazepril may inhibit the high expression of water channel-2 in kidney. |
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