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Dr. Manfrini shares “Endogenous ouabain (EO) is a steroid hormone secreted by the adrenal glands, usually associated with adverse cardiovascular effects. However, recent studies have highlighted its possible role in blood pressure control and in cardio-renal damage, and it seems to be involved in the adaptive response to hypoxia.

The aim of this study is to detect the EO in human and animal models of hypoxia. We collected blood samples from seven competitive elite apnea divers (Italian National Apnea Team, FIPSAS, CONI; two world-renowned record-holders), 11 noncompetitive elite apnea divers (Apnea Free, Water Instinct, and Free Divers Italia), and 26 healthy control subjects. Animal blood samples were collected from 16 common bottlenose dolphins (Tursiops truncatus), one common seal (Phoca vitulina), one gray seal (Halichoerus grypus), one South African fur seal (Arctocephalus p. pusillus) and one California sea lion (Zalophus californianus) kept under human care (Zoomarine Italia, Oltremare, and Acquario di Genova), and 11 wild loggerhead sea turtles (Caretta caretta) hosted in two rescue centers (Rescue Center of Centro Studi Cetacei Onlus and RC of Zoomarine Trust Onlus). We measured EO plasma concentrations with a Scintillation Proximity Assay.

Herein, we demonstrate, for the first time, that different taxa, phylogenetically distant from each other and which perform apneas without reporting neurological damages, express EO. Our findings, although preliminary, are in line with the recently emerging hypothesis on a possible role of EO in the adaptive response to hypoxia and represent a helpful hint for future investigations aimed to identify novel molecules useful to treat very disabling pathological conditions such as idiopathic pulmonary arterial hypertension or obstructive sleep apnea.”

We thank Dr. Manfrini for sharing this information as well as the photographs. Photo credits: dolphin, sea lion (V. Manfrini), sea turtle (P. Saviano), and human divers (black and white image by A. Lufi; photo courtesy of M. Rum; color image by M. Cecconi; photo courtesy of S. Arrigoni; with fishes: photo by V. Truchet; photo courtesy of G. Genoni).