Sex chromosome complement involvement in vasopressin gene expression induced by water deprivation

Abstract

Vasopressin (AVP) is involved in the control of blood pressure and water balance. Basic and clinical data suggest there are sex differences in the expression and function of AVP that cannot be entirely explained solely as a result of gonadal steroid action. This study aimed to define whether sex chromosome complement (SCC) may differentially modulate sex differences in the vasopressin gene expression in response to osmotic stimulation.In order to evaluate whether SCC may differentially modulate vasopressin gene expression we used mice of the “four core genotype” model, in which the effect of gonadal sex and SCC are dissociated, allowing comparisons of sexually dimorphic traits between XX and XY females as well as in XX and XY males. Comparing these genotypes, it is possible to segregate the role of a) SCC (comparing mice with the same gonadal type but different SCC: XX vs. XY) b) sex (females vs. male) and c) the interaction of SCC and sex.To remove the activational effects of sex hormones, that might mask the modulatory action of SCC and the organizational hormonal effects, mice were gonadectomized and 15 days later were submitted to a water deprivation protocol (DEP group). Control groups remained with access to water and normal diet (CON group). Twenty four hours later, brains and plasma of all groups were collected to assess plasma electrolytes and osmolality and to evaluate relative gene expression of AVP at the supraoptic (SON) and paraventricular nuclei (PVN).The statistical analysis showed a significant effect of treatment for both, osmolality and plasma Cl− levels {F(1,40)=4,91 p <0,05; F(1,39)=4,03 p <0,05 respectively, n=6/group.}, however no sex nor SCC effects were observed. On the contrary, a significant effect of the interaction of treatment and SCC factors was observed in the AVP genetic expression at SON {F(1,13)=5,91 p<0,05} n=3–4/group}. Regardless of sex (male or female) XY‐DEP mice (XY‐male and XY‐female) expressed higher AVP mRNA levels compared to XY‐CON animals. However, XX mice (both XX‐male and XX‐female) showed similar levels of AVP mRNA expression for both controls and deprived groups (XX‐CON and XX‐DEP). At the PVN no statistical significant differences were observed. These results reveal a modulatory effect of sex chromosome complement on water deprived AVP gene expression within the SON, what may underlie sex differences in the regulation of vasopressin secretion.Support or Funding InformationSupported by: ANPCyT, ISN, SECyT, Mincyt‐Cba, CnPq, CONICET.