Objective: To investigate the changes of nitric oxide (NO) and nitric oxide synthase (NOS) in vascular smooth muscle cells (VSMCs) of the essential hypertension (EH) patients, determine the effect of arginine vasopressin (AVP) on NO synthesis, and evaluate their significance in the pathogenesis of hypertension.
Methods: VSMCs of EH and normotensives (NT) were isolated by compound collagenase method and cultured in vitro. We detected the NO concentration and the activity of NOS in cell culture medium and determined the effects of AVP on NO synthesis and NOS activity.
Results: NO concentration and the activity of NOS in VSMCs of EH were 0.84 nmol/2.5 x 10(6) cells +/- 0.08 nmol/2.5 x 10(6) cells and (0.23 nmol/min +/- 0.08 nmol/min per 2.5 x 10(6) cells respectively, which were significantly lower than in VSMCs of NT (2.48 nmol/2.5 x 10(6) cells +/- 0.19 nmol/2.5 x 10(6) cells, 0.37 nmol/min +/- 0.06 nmol/min per 2.5 x 10(6) cells, respectively, both P < 0.01). Under AVP induced conditions, NO concentration 3.89 +/- 0.33 nmol/2.5 x 10(6) cells and NOS activity 1.81 nmol/min 2.5 x 10(6) cells +/- 0.09 nmol/min 2.5 x 10(6) cells) in VSMCs of EH were significantly lower than in VSMCs of NT (9.09 nmol/2.5 x 10(6) +/- 0.75 nmol/2.5 x 10(6) cells), 2.80 nmol/min 2.5 x 10(6) cells +/-0.21 nmol/min 2.5 x 10(6) cells, respectively, both P < 0.01). NO concentration and NOS activity in VSMCs of both EH and NT group increased in a culture-time-dependent and AVP-concentration-dependent manner (both P < 0.01). NO concentrations in VSMCs of EH in different culture time increased with the enhancement of NOS activity, and there was significant positive relevance between them (4 h r = 0.940, P < 0.01; 8 h r = 0.993, P < 0.01.
Conclusion: NOS-NO system of EH, with attenuated responsiveness to AVP, is probably abnormal in structure or function, and is involved in the pathogenesis of essential hypertension.