Dramatic and vascular bed-specific hemodynamic changes occur in pregnancy and hypertension of pregnancy (HtP). As the myosin phosphatase (MP) is the primary effector of smooth muscle relaxation, and a key target of signaling pathways that regulate vascular tone, we hypothesized that MP expression would be altered in these conditions. The abundance of the targeting/regulatory subunit of MP (MYPT1) mRNA and protein were increased 1.7-2.0 fold specifically in the uterine arteries (UA) of late pregnant rats without isoform switching. In a model of HtP in which nitric oxide (NO) synthesis is blocked by the chronic administration of L-NAME, MYPT1 was down-regulated and switched to the splice variant isoform that codes for the C-terminal leucine zipper (LZ) motif. This was associated with increased sensitivity of the main UA and its sub-branches to the vaso-relaxant effects of the NO donor drug sodium nitroprusside (SNP). This difference was abolished by pre-treatment with the phosphatase inhibitor Tautomycetin. The sensitivity of relaxation to the NO second messenger cGMP was also increased under calcium clamp conditions in permeabilized UA, indicating heightened activation of MP. The changes in MP expression in HtP were largely prevented by treatment with the anti-hypertensive medicine hydralazine. We propose that MYPT1 isoform switching is an adaptive response to reduce vascular resistance and maintain uterine blood flow in the setting of hypertension triggered inward remodeling of the UA in hypertension of pregnancy.