Immunocytochemical localization of endogenous ouabain in the tissues of SD rats

Objective: To observe the localization of endogenous ouabain (EO) in the some tissues of SD rats. Methods: Immunohistochemical ABC method was used with a high-specify rabbit antiserum against ouabain. Results: Ouabain-like immunoreactivities (OLI) were observed in the inner zone of adrenal cortex, known as the zone reticularis. The low level of OLI could be found in the posterior pituitary of SD rat, and no OLI in the hypothalamus, kidney, cardiac muscle and artery. Conclusion: OLI were located in the zone reticularis of rat adrenal cortex. This morphological evidence supports that EO is a novel adrenocortical steroid hormone.