Effect of inhaled nitric oxide on cerebrospinal fluid and blood nitrite concentrations in newborn lambs.

Inhaled nitric oxide (iNO) has many extrapulmonary effects. As the half-life of nitric oxide (NO) in blood is orders of magnitude less than the circulation time from lungs to the brain, the mediator of systemic effects of iNO is unknown. We hypothesized that concentrations of nitrite, a circulating byproduct of NO with demonstrated NO bioactivity, would increase in blood and cerebrospinal fluid (CSF) during iNO therapy. iNO (80 ppm) was given to six newborn lambs and results compared with six control lambs. Blood and CSF nitrite concentrations increased 2-fold in response to iNO. cGMP increased in blood but not CSF suggesting brain guanylate cyclase activity was not increased. When sodium nitrite was infused i.v. blood and CSF nitrite levels increased within 10 min and reached similar levels of 14.6 +/- 1.5 microM after 40 min. The reactivity of nitrite in Hb-free brain homogenates was investigated, with the findings that nitrite did not disappear nor did measurable amounts of s-nitroso, n-nitroso, or iron-nitrosyl-species appear. We conclude that although nitrite diffuses freely between blood and CSF, due to its lack of reactivity in the brain, nitrite's putative role as the mediator of the systemic effects of iNO is limited to intravascular reactions.

Increased innervation and ripening of the prepartum murine cervix.

OBJECTIVE: Ripening of the cervix before birth is coincident with reduced collagen content and leukocyte immigration, characteristics that are analogous to a neurogenic inflammatory-like process. We sought to assess the morphologic relationship between innervation and remodeling of the peripartum cervix. METHODS: Cervix was obtained from C3H/HeN mice on days 15 and 18 of pregnancy, 1 day postpartum, and from non-pregnant controls. Tissues were immersion-fixed, paraffin-embedded, and some sections stained with Picrosirius red to assess collagen content and complexity of organization. By image analysis of optical density, collagen content and structure were significantly decreased by the day before birth. Other sections were processed to visualize nerve fibers by immunohistochemistry with antibodies against neuron-specific epitopes, PGP9.5, peripherin, as well as brain nitric oxide synthase (bNOS), calcitonin gene-related peptide (CGRP), and other neuropeptides. Fiber density was assessed stereologically and normalized to cell density in non-pregnant cervix to correct for tissue hypertrophy due to reproductive status. RESULTS: In groups of non-pregnant, day 15 pregnant, and postpartum mice, cervix contained nerve fibers that were immunoreactive for the pan-neural markers PGP9.5 and peripherin. Punctate and beaded varicosities were sparsely distributed in stroma, subepithelium, and in proximity to vascular structures. By day 18 of pregnancy, 1 day before birth, fiber density was increased fourfold or more compared to other groups. bNOS fibers and, to a lesser extent, CGRP accounted for most of the increased innervation of the murine cervix by the day before birth, a period when macrophage numbers are enhanced. CONCLUSIONS: The findings suggest that increased bNOS and CGRP innervation contribute to early inflammatory-like processes that ripen the cervix before birth.