Changes in plasma nitric oxide and nitric oxide synthase activity in children with orthostatic hypotension / 中华实用儿科临床杂志

ABSTRACT

Objective To explore the changes in plasma nitric oxide (NO) and nitric oxide synthase (NOS) activity in children with orthostatic hypertension(OHT) and the relationship with blood pressure changes.Methods The OHT group included 51 children who were diagnosed OHT in in-patient and out-patient departments of Peking University First Hospital from Jun.2012 to Jun.2013.Their age range was (12 ± 2) years.At the same time,control group consisted of 28 normal children who received physical examination with their age range of(12 ± 1) years.The diagnosis of OHT was based on the clinical manifestation and head-up tests.Plasma NO was determined by using a nitrate reductase method and plasma NOS activity by a chemical colorimetric method.Results 1.There were no significant differences between OHT group and control group in age,sex ratio,height,weight and body mass index (all P ＞0.05).2.In OHT children,the upright systolic blood pressure was higher than that of the supine [(114 ± 10) mmHg vs (104 ± 9) mmHg,t =-12.853,P ＜ 0.001],and the upright diastolic blood pressure was higher than that of the supine[(73 ±7) mmHg vs(59 ± 8) mmHg,t =-21.859,P ＜0.001].3.Plasma NO level and NOS activity,however,were significantly lower in OHT group than those in the control group [NO(28.947 ± 6.031) μmol/L vs (35.216 ±6.662) μmol/L,t =4.257,P ＜ 0.001 ; NOS activity(14.753 ± 3.060) U/mL vs (17.560 ± 4.253) U/mL,t =3.026,P =0.006].4.There was significantly negative correlation between plasma NO and the upright systolic blood pressure(r =-0.276,P ＜ 0.05) and the systolic blood pressure change (r =-0.280,P ＜ 0.05).Conclusions Plasma NO level and NOS activity were significantly lower in OHT children than those in control group.The abnormal vascular endothelial function may play an important role in OHT in children.