Traditional Nigerian natron and potash: Effects on uterine smooth muscle and their histopathology and immunohistochemical responses in Wistar rats

Natron (sodium carbonate) and potash (potassium carbonate) are traditionally used by birth attendants in Nigeria to facilitate labor and manage menstrual disorders. However, their uterine activity and potential risks to uterine integrity remain poorly characterized. This study evaluated the effects of natron and potash on uterine smooth muscle contractility and examined associated histopathological and immunohistochemical changes in rat uterine tissue. The cationic composition (Na + , K + , Ca 2+ ) of different natron varieties and potash was quantified. Uterine contractility was assessed in vitro using isolated rat uterine smooth muscle preparations in organ baths. Substances with contractile activity underwent acute toxicity testing before in vivo evaluation. Fifty adult female Wistar rats (nulliparous and multiparous) were randomized into ten groups and administered 5% or 10% natron or potash for eight weeks. Uterine tissues were analysed histologically and immunohistochemically using progesterone receptor and Vimentin markers. Potash and one natron variety shared similar electrolyte profiles and elicited significant uterine contractions, whereas other natron varieties induced smooth muscle relaxation. Chronic exposure resulted in marked uterine remodelling, including altered endometrial-to-myometrial ratios, glandular hyperplasia, fibrocollagenous stromal deposition, and inflammatory infiltration. Progesterone receptor and Vimentin expression increased in a concentration-dependent manner, with greater immunoreactivity observed in nulliparous rats. Natron exhibits heterogeneous uterine effects that are strongly influenced by its cationic composition. While some varieties and potash demonstrate uterotonic activity consistent with traditional use, the associated structural remodelling and inflammatory changes highlight potential adverse uterine consequences, underpinning the need for rigorous safety evaluation prior to clinical application.