Oxytocin is a cardiovascular hormone

Abstract

Oxytocin (OT), a nonapeptide, was the first hormone to have its biological activities established and chemical structure determined. It was believed that OT is released from hypothalamic nerve terminals of the posterior hypophysis into the circulation where it stimulates uterine contractions during parturition, and milk ejection during lactation. However, equivalent concentrations of OT were found in the male hypophysis, and similar stimuli of OT release were determined for both sexes, suggesting other physiological functions. Indeed, recent studies indicate that OT is involved in cognition, tolerance, adaptation and complex sexual and maternal behaviour, as well as in the regulation of cardiovascular functions. It has long been known that OT induces natriuresis and causes a fall in mean arterial pressure, both after acute and chronic treatment, but the mechanism was not clear. The discovery of the natriuretic family shed new light on this matter. Atrial natriuretic peptide (ANP), a potent natriuretic and vasorelaxant hormone, originally isolated from rat atria, has been found at other sites, including the brain. Blood volume expansion causes ANP release that is believed to be important in the induction of natriuresis and diuresis, which in turn act to reduce the increase in blood volume. Neurohypophysectomy totally abolishes the ANP response to volume expansion. This indicates that one of the major hypophyseal peptides is responsible for ANP release. The role of ANP in OT-induced natriuresis was evaluated, and we hypothesized that the cardio-renal effects of OT are mediated by the release of ANP from the heart. To support this hypothesis, we have demonstrated the presence and synthesis of OT receptors in all heart compartments and the vasculature. The functionality of these receptors has been established by the ability of OT to induce ANP release from perfused heart or atrial slices. Furthermore, we have shown that the heart and large vessels like the aorta and vena cava are sites of OT synthesis. Therefore, locally produced OT may have important regulatory functions within the heart and vascular beds. Such functions may include slowing down of the heart or the regulation of local vascular tone. Correspondence

Nitrergic modulation of vasopressin, oxytocin and atrial natriuretic peptide secretion in response to sodium intake and hypertonic blood volume expansion

“…Oxytocin (OT) is also involved in hydromineral homeostasis and vascular and cardiac relaxation (17)(18)(19)(20)(21)(22)(23). It has long been recognized that OT increases renal electrolyte excretion in various species, and that the natriuretic and kaliuretic effects are AVP independent.…”

Oxytocin in cardiac ontogeny

“…In addition, we have demonstrated that in isolated, perfused hearts, an OT antagonist (OTA) blocks basal ANP release (7), suggesting the presence of local OT in the heart. Further study revealed cardiac OT synthesis (8), with OT being detected in the medium of cultured neonatal rat cardiomyocytes (9).…”

Monitoramento não invasivo baseado na biorreatância revela instabilidade hemodinâmica significativa durante cesárea eletiva sob raquianestesia

“…The fall in cardiac output in our patients was primarily due to the fall in heart rate, due to the reflex bradycardia associated with phenylephrine administration. Thomas et al studied the effects of phenylephrine and ephedrine on maternal cardiac output using cross-sectional and Doppler echocardiography 17 . Bradycardia secondary to phenylephrine administration was treated with atropine in 11 of 19 patients, and as a result the decreases in cardiac output were comparable to those with ephedrine administration.…”

“…Oxytocin receptors are widely present in the cardiovascular system 18 . The activation of oxytocin receptors in the heart releases atrial natriuretic peptide; on the endothelial receptors, it stimulates the release of nitric oxide 17 . As a result, vasodilation is observed.…”