Complex mechanisms appear to regulate the perivascular adipose tissue (PVAT) function and more than one pathway, including reactive oxygen species (ROS), may be responsible for the effect of PVAT on vascular physiology (1, 2). We have found sex differences in the regulation of vascular tone by PVAT in the porcine coronary artery (PCA) (Data not published). As there are sex differences in oxidative stress in the vasculature (3), the aim of the present study was to determine whether there are sex differences in production of ROS from NADPH oxidase (Nox) in PVAT and the effect on vasomotor function of isolated porcine coronary artery. Coronary arterial responses to PVAT were recorded in an isometric tension recording system in the presence and absence of a range of Nox inhibitors. Nox activity (superoxide anion production (O-2)) in PVAT and PCA homogenates was assessed using lucigenin-enhanced chemiluminescence. Western immunoblotting was performed to examine the expression of different Nox isoforms in PVAT and PCAs. t-test or ANOVA was used to analyse the data depending on the number of factors analysed. Data are expressed as mean±S.E.M. In male and female PCAs, PVAT caused significant vasoconstrictor responses (p<0.001,n=6). Pre-incubation with non-selective NOX antagonist diphenyleneiodonium (DPI) (10µM) (p<0.01,n=5), selective NOX1 antagonist (ML171) (100µM) (p<0.001,n=6), selective NOX2 antagonist PhoxI2 (100µM) (p<0.001,n=6) and selective Nox1 and Nox4 antagonist (GKT137831) (10µM) (females (F):p<0.01; males (M):p<0.001,n=8) significantly reduced PVAT-induced vasoconstriction in PCAs from both females and males. NOX1, NOX2 and NOX4 were expressed in PVAT with no difference detected between females and males (n=6F and 5M). However, in PCAs, NOX1 expression was greater in females (p<0.05,n=6F and 5M) whilst NOX4 was higher in males (p<0.01,n=6F and 5M). NOX2 was expressed equally in PCAs from different sexes (n=6F and 5M). NOX activity was detected in PVAT and PCAs with no sex differences. DPI (10µM), ML171 (100µM) and phox-I2 (100M) reduced significantly O-2 production in PVAT and PCA from both sexes (Table 1). In contrast, GKT137831 did not inhibit O-2 production in PVAT and PCA from both sexes (Table 1). This study illustrates that PVAT is an important source of Nox-derived ROS that can induce contraction of porcine coronary artery with no effect of sex difference on the crosstalk between PVAT and vascular tone despites a significant variations in the expression of NOXs isoforms.