Plasma hydrogen sulfide, nitric oxide, and thiocyanate levels are lower during pregnancy compared to postpartum in a cohort of women from the Pacific northwest of the United States

Abstract

Aims: Pregnancy alters multiple physiological processes including angiogenesis, vasodilation, inflammation, and cellular redox, which are partially modulated by the gasotransmitters hydrogen sulfide (H₂S) and nitric oxide (NO). In this study, we sought to determine how plasma levels of H₂S, NO, and the H₂S-related metabolites thiocyanate (SCN^-), and methanethiol (CH₃SH) change during pregnancy progression.

Materials and methods: Plasma was collected from 45 women at three points: 25-28 weeks gestation, 28-32 week gestation, and at ≥3 months postpartum. Plasma levels of H₂S, SCN^-, and CH₃SH were measured following derivatization using monobromobimane followed by LC-MS/MS. Plasma NO was measured indirectly using the Griess reagent.

Key findings: NO and SCN^- were significantly lower in women at 25-28 weeks gestation and 28-32 weeks gestation than postpartum while plasma H₂S levels were significantly lower at 28-32 weeks gestation than postpartum. No significant differences were observed in CH₃SH.

Significance: Previous reports demonstrated that the production of H₂S and NO are stimulated during pregnancy, but we observed lower levels during pregnancy compared to postpartum. Previous reports on NO have been mixed, but given the related effects of H₂S and NO, it is expected that their levels would be higher during pregnancy vs. postpartum. Future studies determining the mechanism for decreased H₂S and NO during pregnancy will elucidate the role of these gasotransmitters during normal and pathological progression of pregnancy.

Keywords: Hydrogen sulfide; Hypertension; Methyl sulfide; Nitric oxide; Postpartum; Preeclampsia; Pregnancy; Thiocyanate.