ACE2 expression in the kidneys of pregnant and postpartum rats: Physiological and pathological significance during pregnancy

Pregnancy is associated with changes in systemic hemodynamics, such as an increase in plasma volume and decrease in blood pressure because of peripheral vasodilation. However, little is known about the mechanisms underlying the changes in renal hemodynamics, such as increases in renal blood flow and the glomerular filtration rate (GFR). Angiotensin-converting enzyme 2 (ACE2), a transmembrane glycoprotein involved in vasodilation, also acts as a receptor for the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during coronavirus disease 2019 (COVID-19) infection. Here, we showed that in pregnant rats the renal arterioles and venules as well as the glomerular capillaries were markedly dilated, indicating renal vasodilation. Immunohistochemistry demonstrated increased ACE2 and angiotensin (1-7) (Ang (1-7)) expression within the proximal renal tubules during pregnancy. As these proteins exert vasodilatory properties, they are considered responsible for renal vasodilation and the subsequent increase in GFR. Further, the similar distribution and enhanced expression of ACE2 and transmembrane protease serine 2 (TMPRSS2) in the proximal renal tubules during pregnancy suggests their roles in the development of acute kidney injury following COVID-19 infection in pregnancy. Overall, this study highlights the physiological and pathological significance of ACE2 during pregnancy.