Vasopressinergic sexual dimorphism: Sex chromosome complement and organizational hormonal effects

This study aimed to analyze the role of the sex chromosomes (SCC: XX/XY) and the interaction with organizational hormonal effects on Avp gene expression at the supraoptic (SON) and paraventricular nuclei (PVN) due to water deprivation, as well as on the vasopressinergic sexually dimorphic antidiuretic and pressor responses. For this purpose, we used gonadectomized (GDX) transgenic mice of the "four core genotypes" model, in which the effect of gonadal sex and SCC are dissociated.

A significant interaction between treatment and SCC on Avp gene expression at the SON was observed. Regardless of sex, XX mice showed higher basal expression than those with XY; however after water deprivation no changes in mRNA Avp expression were observed in the XX group, while an increase for XY was reported. At the PVN an interaction of SCC, organizational hormonal, and treatment factors was observed, revealing an increase in Avp gene expression in the XY-GDX male DEP group.

Although no SCC or organizational hormonal effects were observed on the demopressin-antidiuretic response and renal Avpr2 mRNA expression, an interplay of organizational hormonal and SCC factors in short and medium-term vasopressin-blood pressure regulation were reported. XX-GDX females showed a facilitated vasopressin-bradycardic baroreflex response when compared to the other genotypes. Furthermore, although vasopressin continuous infusion resulted initially in the expected increase in the percentage change in MAP in all genotypes, in XX-GDX male and female this increase was sustained until the 30-min infusion, while in XY-GDX male and in XY-GDX female mice a decrease in MAP was observed.