Pathophysiology of chronic nitric oxide synthase inhibition-induced fetal growth restriction in the rat

Objective. To evaluate the pathophysiology of chronic nitric oxide synthase (NOS) inhibition-induced fetal growth restriction (FGR) in the rat. Methods. Timed-pregnant rats received L-NAME (2.5 mg/kg/h) with or without endothelin (ET-1) receptor A (ETA) antagonist from day 14 to 21 of gestation. In separate groups, ETA antagonist and/or L-NAME were discontinued on day 18. On day 21 fetal and placental weights, and maternal and fetal plasma nitrate/nitrite (NOx) were determined. Results. L-NAME led to FGR, and decreased maternal and fetal NOx. Maternal NOx was further decreased when ETA antagonist was co-administered with L-NAME. ETA antagonism along with L-NAME did not impact fetal growth. Discontinuation of L‐NAME on day 18 resulted in normal fetal and placental growth at day 21 and an increase of maternal NOx. Simultaneous cessation of both NOS inhibition and ETA antagonism on day 18 produced FGR at day 21, whereas continuation of ETA antagonism after discontinuation of L-NAME resulted in normal fetal growth. Conclusions. NOS inhibition in the pregnant rat leads to decreased maternal and fetal nitric oxide (NO) production and FGR. The effects of NOS inhibition on fetal growth are reversible, and are mediated at least in part by ET-1. With chronic NOS inhibition, ETA antagonism improves but does not normalize fetal growth, and may allow increased access of L-NAME to the fetal compartment. Continued access of L-NAME to the fetal compartment may limit the effect on fetal growth of any therapeutic intervention in this model of FGR

The AXB and BXA set of recombinant inbred mouse strains.

The recombinant inbred (RI) set of strains, AXB and BXA, derived from C57BL/6J and A/J, originally constructed and maintained at the University of California/San Diego, have been imported into The Jackson Laboratory and are now in the 29th to 59th generation of brother-sister matings. Genetic quality control testing with 45 proviral and 11 biochemical markers previously typed in this RI set indicated that five strains had been genetically contaminated sometime in the past, so these strains have been discarded. The correct and complete strain distribution patterns for 56 genetic markers are reported for the remaining RI strain set, which consists of 31 living strains and 8 extinct strains for which DNA is available. Two additional strains, AXB 12 and BXA 17, are living and may be added to the set pending further tests of genetic purity. The progenitors of this RI set differ in susceptibility to 27 infectious diseases as well as atherosclerosis, obesity, diabetes, cancer, cleft palate, and hydrocephalus. Thus, the AXB and BXA set of RI strains will be useful in the genetic analysis of several complex diseases