Pregnancy influence on the vascular interactions between nitric oxide and other endothelium-derived mediators in rat kidney

Abstract

Peripheral vascular resistance and sensitivity to circulating pressor and vasoconstrictor agents are blunted during pregnancy. This has been mainly attributed to an increased production of endothelium-derived mediators. The objective of this work was to evaluate if pregnancy changes the relative participation of nitric oxide (NO) and prostaglandins (PG) in respect to the modulation of the increases in renal perfusion pressure induced by phenylephrine (Phe). Dose-response curves were made with gradually increasing doses of Phe using an isolated kidney preparation in the presence of a NO synthase (NOS) inhibitor (L-NAME, 1 microM), a PG-synthesis inhibitor (indomethacin, 1 microM), both, or neither. Also, renal cyclooxygenase (COX-1 and COX-2) and endothelial NOS (eNOS) expression was determined using PCR. The experiments were done in kidneys from nonpregnant and pregnant rats. Our results showed that the relative participation of renal vasoactive mediators seems to change during pregnancy. We found the presence of a COX-1-dependent vasoconstrictor in the middle of pregnancy that was not found in nonpregnant rats. Our results also suggest that there is increased participation of another renal vasodilator substance, the effect of which is observed when NO or PG synthesis is inhibited during late pregnancy. In addition, an apparent interaction between renal eNOS and COX-1 expression was observed: eNOS expression was diminished, while COX-1 was increased during the 2nd week of pregnancy. In contrast, in kidneys from the 3rd week of pregnancy, the expression of these two enzymes was similar.

Hypertrophy signaling during peripartum cardiac remodeling

“…This differs from the finding in pregnant dogs, wherein LV eNOS protein expression was increased at 60 days gestation (23). Many other studies have shown upregulation of eNOS in aorta and resistance arteries during pregnancy but often a downregulation in organs like the kidney (3,4,24). Therefore, our findings are consistent with published literature.…”

Receptor-Induced Dilatation in the Systemic and Intrarenal Adaptation to Pregnancy in Rats

“…Pregnancy-associated vasodilatation has been attributed, in part, to hormones such as prostaglandins [3], nitric oxide (NO) [3], [4], [5], endothelium-derived hyperpolarizing factor [6], and more recently, relaxin, which is considered an important regulator of renal and cardiovascular function during pregnancy [7], [8]. The serum levels of relaxin increase soon after conception in humans and near day 8 of gestation in rats [9].…”

Chronic Nicotine Exposure Abolishes Maternal Systemic and Renal Adaptations to Pregnancy in Rats

“…In addition, these adaptations are followed by an 80 and 50% rise in the renal plasma flow (RPF) and glomerular filtration rate (GFR), respectively [ 1 ]. Relaxin, estrogen, prostaglandins and nitric oxide (NO) modulate these adaptations [ 2 – 5 ]. Pregnancy also imposes a necessary expansion of the extracellular volume (ECV) by sodium and water retention via mechanisms involving changes in the expression of tubular transporters.…”