ACE2 Expression in the Kidneys of Pregnant and Postpartum Rats: Physiological and Pathological Significance During Pregnancy.

Background/aims: Pregnancy is associated with 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).

Methods: Using rats on pregnancy day 16 and postpartum day 5, we examined the histopathological changes in rat kidneys during and after pregnancy. The expressional changes in renal angiotensin-converting enzyme 2 (ACE2) and angiotensin (1-7) (Ang (1-7)) were examined, together with those of transmembrane protease serine 2 (TMPRSS2).

Results: examined, together with those of transmembrane protease serine 2 (TMPRSS2). Results: 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 Ang (1-7) expression within the proximal renal tubules during pregnancy, which then returned to the virgin levels in the postpartum period. Additionally, the proximal tubular expression of ACE2 and TMPRSS2 was similarly enhanced during pregnancy.

Conclusion: As ACE2 and Ang (1-7) exert vasodilatory properties, they were considered responsible for renal vasodilation and the subsequent increase in GFR. Further, the similar distribution and enhanced expression of ACE2 and TMPRSS2 in the proximal renal tubules during pregnancy suggested their roles in the development of acute kidney injury (AKI) following COVID-19 in pregnancy. This study highlights the physiological and pathological significance of ACE2 during pregnancy.