[A study on the role of contractile and relaxant reaction of umbilical vein in vitro and local changes of nitrix oxide synthase in the pathogenesis of pregnancy induced hypertension].

OBJECTIVE

To study the contractile and relaxant reaction of human umbilical veins in vitro from pregnancy induced hypertension (PIH) patients, pathophysiological significance and the role of local changes of nitric oxide synthase (NOS) in the pathogenesis of PIH.

METHODS

The contractile and relaxant curves of umbilical vein in response to phenylephrine, isoprenaline and acetylcholine were recorded in the PIH group and normal pregnancy group (control group). The maximum effect (Emax) and affinity index (pD2) volume were calculated. Meanwhile, the NOS activity in the blood vessel tissue and the plasma concentration of nitric oxide metabolite (NO2-/NO3-) were examined.

RESULTS

(1) Relaxtant of the Emax of umbilical vein in the control group in response to acetylcholine was (85.0 +/- 15.0)%, pD2 volume was 4.4 +/- 0.5; However, the Emax (70.0 +/- 13.0)% and the pD2 (3.7 +/- 0.6) were significantly lower in the PIH group (P < 0.01). No significant differences of Emax and pD2 were obtained in phenylephrine-induced vessel contraction and isoprenaline-induced relaxation between the groups (P > 0.05). (2) NOS activity of umbilicahich was significantly lower than that from the control group [(0.5 +/- 0.2) nmol.g-1.min-1] (P < 0.01). The plasma NO2-/NO3- concentration was (38.0 +/- 10.0) mumol/L in the PIH group, which was also lower than that in the control group [(56.0 +/- 14.0) mumol/L] (P < 0.01).

CONCLUSIONS

The abnormal function of endothelium system and abnormal metabolism of nitric oxide in blood vessel, which resulted in the decreased endothelium dependent relaxation, might be possible mechanism involved in the pathogenesis of PIH.