Introduction:
Kidney damage during pregnancy constitutes a diagnostic and therapeutic challenge. However, it is not entirely known whether a kidney condition recognised before the pregnancy releases an organism’s response to pregnancy, or whether pregnancy itself worsens kidney function.

Objective:
The aim of the study was immunohistochemical evaluation of cells of kidneys of pregnant rats under the influence of nitric oxide (NO), with measurement of the immunoexpression of cellular stress markers (p-53, HSP 70). The dose of administered L-arginine (NO substrate) was approximated to that applied in obstetrics in gestosis prevention and treatment in pregnant women.

Material and Methods:
60 female rats used in experiment were divided into 6 groups: 3 experimental and 3 control. The females from experimental groups were administered L-arginine (40g/kg, per os) every other day starting from the seventh day or pregnancy. The animals were decapitated on the 10th, 20th day of pregnancy, and 10 days after the delivery. Kidneys taken from decapitated rats were evaluated using the immunohistochemical three step method. HSP 70 and p-53 proteins were detected.

Conclusions:
L-arginine increased the expression of p-53 protein – on the 10th day of pregnancy, which increased at the end of pregnancy; however, 10 days after delivery the level dropped below that observable during physiological pregnancy. Hormonal changes in physiological pregnancy cause an increase in expression of the p-53 (cell stress marker) in the epithelial cells of renal tubules, mainly at the end of pregnancy (20th day). 10 days after the delivery, this expression decreases. The expression of HSP-70 protein increases already on the 10th day of pregnancy and maintains a similar level throughout the pregnancy, but is reduced after the puerperium.