Objective: To explore the role genetic factor plays in the pathogenes is of essential hypertension (EH) among Tibetans and to investigate whether angiotensinogen (AGT) is involved in the pathogenesis of EH.
Methods: A case-control association study was conducted among 353 essential hypertensive subjects and 317 genealogic structure-matched normotensive controls, all of Tibetan nationality. The correlation between polymorphism of M235T and 6A-->G variant in AGT gene and EH susceptibility in Tibetans was examined by polymerase chain reaction ( PCR) and PCR/RFLP (restriction fragment lengths polymorphism) with AspI and BstN I,respectively.
Results: (1) The affection rate of EH among the first-degree relatives of Tibetan EH proband was 43.3%. The heritability of EH was 77.2% +/- 13.3% by Falconer method. (2) The plasma rennin activity and angiotensin II (AngII) level among the EH patients were (1.95 +/- 0.11) microgram .L(-1).h(-1) and (72.6 +/- 4.6) ng/L, all significantly higher than those in the controls [(1. 59 +/- 0.11) microgram .L(-1).h(-1) and (51.7 +/- 4.6) ng/L, all P < 0.05].(3) The -6G allele frequency in the promoter of AGT gene was higher in EH group than in the control group (0.36 vs 0.27, kappa(2) = 9.35, P < 0.01). There was a weak association between -6A -->G variant and the plasma AngII level, and there was no significant difference in the genotype distribution and allele frequency of M235T variant between the hypertensive and normotensive groups (P > 0.05).
Conclusion: Genetic factor plays an important role in the pathogenesis of essential hypertension and angiotensinogen gene might be one of the most key susceptibility genes for essential hypertension in Tibetan.