Anti‐Contractile Effect of Perivascular Adipose Tissue in Pregnant Rat Aorta

It is now known that PVAT releases a variety of factors and inhibits contraction induced by a variety of vasoconstrictors. The present investigation examines the effect of pregnancy on the anti-contractile effect of PVAT. Aorta segments, with or without PVAT, from non-pregnant and pregnant rats were set up in tissue baths for isometric tension recording. 5-Hydroxytryptamine (5-HT) induced concentration-dependent contractions were reduced in aorta segments with PVAT attached but this anti-contractile effect of PVAT was impaired in segments from pregnant rats. 4-AP, inhibitor of Kv channels, enhanced 5-HT-induced contractions of aorta segments from pregnant and non-pregnant rats only when PVAT was attached suggesting modulation of 5-HT-induced contraction by a substance (ADRF) released by PVAT which subsequently activated Kv channels to produce an anti-contractile effect. There was no significant difference between the potentiating effects of 4-AP on 5-HT-induced contractions in aorta segments (with PVAT) from pregnant and non-pregnant rats. This is consistent with the fact that there was no significant difference in the expression of Kv7 channels in aorta segments (with PVAT) from pregnant and non-pregnant rats. This would rule out impaired expression and function of Kv channels as the underlying factor for the loss of anti-contractile effect of PVAT. It was therefore concluded that the loss of anti-contractile effect of PVAT in aorta segments from pregnant rats may be due to the release of a contracting factor or loss of a relaxing factor by PVAT. Supported by a grant (MR 01/12) from Kuwait University Research sector