SUPPRESSION OF ANGⅡ AFTER ACUTE SALINE LOAD ASSOCIATED WITH THE CHANGES OF PLASMA ANP AND SODIUM METABOLISM IN SALT-SENSITIVE HYPERTENSION PATIENTS

Objective To observe the changes of plasma AngⅡ,ANP and their relationship with urine sodium excretion in salt sensitive hypertension. Methods The salt sensitivity was determined by acute saline loading test in 173 primary hypertensives of Stage Ⅰ or Stage Ⅱ. Plasma AngⅡand ANP was determined by radioimmunoassay. Results After acute salt load, AngⅡ was suppressed inadequately. The plasma ANP secretion was not increased. The urine sodiun excretion was delayed, Na + in RBC was increased in salt sensitive subjects. The plasma ANP was decreased in the salt sensitive subjects without AngⅡ suppressed. The 24 hours urine sodium excretion was lower than those AngⅡ suppressed.Conclusion The changes of plasma RAS are not homogeneous after salt load. Those without the plasma AngⅡ suppressed have more severe sodium metabolism abnormalities and the endogenous ANP secretion is impaired in salt sensitive patients.

RENAL ENDOGENOUS ET-1 AND URINARY SODIUM EXCRETION AND MICROALBUMINURIA IN HUMAN SALT-SENSITIVE HYPERTENSION

Objective To investigate the urinary endothelin-1 (ET-l ) excretion and urinary sodium excretion, microalbuminuria and ambulatory blood pressure(ABP) in salt-sensitive(SS) hypertension patients. Methods Twen- ty-one cases of normotensive subjects and 32 cases of uncomplicated hypertensive patients were recruited in this study. Salt sensitivity was determined by acute venous saline loading test. Before saline loading, 24-hour ABP mea- surements were performed. Urine samples were collected to assay ET-1,urinary sodium excretion and urinary albumin excretion(UAF). Results Compared to slat-resistant(SR) subgroup, SS showed low urinary ET-1 excretion in nor- motensive group (P<0.05) or hypertensive group (P<0.01),regardless or saline loading or not. The nighttime MAP of SS was higher than SR subgroup in normotensive or hypertensive group. Urinary sodium excretion during 4h of saline loading was significantly lower in SS than that in SR hypertensive patients (P<0.05). Twenty-four-hour UAE of SS patients was higher than SR group (P<0.01). Results of further correlation analysis indicated that the urinary ET-1 excretion was positively related to urinary sodium content and negatively to ABP and UAE. Conclusion Uri- nary ET-1 is low in SS normotensives or hypertension patients,which may play a role in renal sodium retention and renal impairment or SS hypertension patients.

Characterization and Mapping of a Salt-Sensitive Mutant in Rice (Oryza sativa L.)

A salt-sensitive mutant designated rice salt sensitive 2 （rss2） was isolated from the M2 generation of the rice cultivar Nipponbare （Oryza sativa L. ssp. japonica） mutagenized with ethyl methanesulfonate （EMS）. This mutant exhibited a greater decrease in salt tolerance with a significant increase in Na＋ content in its shoots. Genetic analysis indicated that the increase in Na＋ in rss2 was controlled by a single recessive gene. Further genome-wide analysis of the linkage map constructed from the F2 population of rss2/Zhaiyeqing 8 （ZYQ8） showed that two quantitative trait loci （QTLs） on chromosomes 1 and 6 were responsible for the Na＋ concentration in shoots, which explained 14.5% and 53.3%, respectively, of the phenotypic variance. The locus on chromosome 1, but not that on chromosome 6, was also detected in the F2 population of Nipponbare/ZYQ8, suggesting that the QTL on chromosome 6 was responsible for the salt sensitivity in rss2. By analyzing the recombination events in 220 mutant individuals of an enlarged mapping population of rss2/ZYQ8, the rss2 locus was precisely mapped to an interval of 605.3 kb between insertion/deletion （InDel） markers IM21962 and IM22567. This finding will facilitate the cloning of the rss2 locus and provide insight into the physiological mechanisms of salt sensitivity in rice.

Sodium Stress in the Halophyte Thellungiella halophila and Transcriptional Changes in a thsos1-RNA Interference Line

The plasma membrane Na＋/H＋-antiporter salt overly sensitive1 （SOS1） from the halophytic Arabidopsis-relative Thellungiella halophila （ThSOS1） shows conserved sequence and domain structure with the orthologous genes from Arabidopsis thaliana and other plants. When expression of ThSOSt was reduced by RNA interference （RNAi）, pronounced characteristics of salt-sensitivity were observed. We were interested in monitoring altered transcriptional responses between Thellungiella wild type and thsost-4, a representative RNAi line with particular emphasis on root responses to salt stress at 350 mmol/L NaCI, a concentration that is only moderately stressful for mature wild type plants. Transcript profiling revealed several functional categories of genes that were differently affected in wild-type and RNAi plants. Down-regulation of SOS1 resulted in different gene expression even in the absence of stress. The pattern of gene induction in the RNAi plant under salt stress was similar to that of glycophytic Arabidopsis rather than that of wild type Thellungiella. The RNAi plants failed to down-regulate functions that are normally reduced in wild type Thellungiella upon stress and did not up-regulate functions that characterize the Thellungiella salt stress response. Metabolite changes observed in wild type Thellungiella after salt stress were less pronounced or absent in RNAi plants. Transcript and metabolite behavior suggested SOS1 functions including but also extending its established function as a sodium transporter. The down-regulation of ThSOS1 converted the halophyte Thellungiella into a salt-sensitive plant.