Nitric oxide is released in regenerating liver after partial hepatectomy

Abstract

The induction of hepatic nitric oxide synthase (NOS) and the biosynthesis of nitric oxide (NO) were studied in liver after partial hepatectomy (PH). NOS activity in the liver remnant was observed 4 to 6 hours after PH, and no differences were evidenced between the proximal and distal surgical areas. The form of NOS expressed in liver was independent of calcium and calmodulin, and the messenger RNA levels were first detected 2 hours after hepatectomy using a probe corresponding to the cytokine-induced macrophage NOS. The seric concentration of nitrites remained unchanged after hepatectomy, whereas the content in nitrates and in S-nitrosylated proteins progressively increased in parallel with the NOS activity. The spectra of hemoglobin in the 400-to 460-nm region failed to exhibit the characteristic shift caused by the formation of the nitrosyl-hemoglobin complex, suggesting that NO was rapidly metabolized in liver. Treatment of the animals with substrate analogue NOS inhibitors blocked the pattern of DNA ploidy elicited after hepatectomy, suggesting a role for NO in the regenerative process. Peritoneal resident macrophages were used as an alternative reporter cell system for the assessment of NOS expression. Incubation ex vivo of peritoneal macrophages from animals that underwent hepatectomy induced the expression of NOS in a cytokine-modulated fashion, suggesting that macrophages were primed as a result of the hepatectomy. When peritoneal macrophages from control rats were incubated with the sera of animals that underwent hepatectomy, a time-dependent induction of NOS was observed, with a maximal induction corresponding to sera collected 2 hours after PH. These results indicate that NO might be involved in the control of early responses after PH.

NO sensitizes rat hepatocytes to proliferation by modifying S-adenosylmethionine levels

“…3°-33 A combination of both cytokines has been shown to induce the expression of the iNOS gene, 34 which also occurs in the liver after PH before the onset of DNA synthesis) 5 NO production seems to be an important response of the remaining liver parenchyma because inhibition of iNOS with L-NAME decreases hepatocyte proliferation and iNOS knockout mice display impaired liver regeneration after PH. 5,6 In iNOS knockout mice, hepatocytes undergo necrosis and apoptosis after PH, indicating that the production of N O was essential to protect hepatocytes from death after liver resection. 6 Our present observations suggest that, in addition to this protective role, N O could also play an important function in the sensitization of the hepatocyte to the mitogenic action of growth factors such as HGF and TGFo~.…”

Evidence for Common Mechanisms in the Transcriptional Control of Type II Nitric Oxide Synthase in Isolated Hepatocytes

“…Determination of NO-NO release was determined spectrophotometrically by the accumulation of nitrite and nitrate in the medium (phenol red-free) as follows: 250 l of culture medium were transferred to 1.5-ml Eppendorf tubes and the nitrate was reduced to nitrite with 0.5 units of nitrate reductase (Boehringer Mannheim) in the presence of 50 M NADPH and 5 M FAD (6,16). After oxidation of the NADPH excess (which interferes with the chemical determination of nitrite) with 0.2 mM pyruvate and 1 g of lactate dehydrogenase, nitrite was determined with Griess reagent (16) by adding 1 mM sulfanilic acid and 100 mM HCl (final concentration).…”

Re-evaluation of Arginine Requirements for Broilers Exposed to Hypobaric Condition during the 3-to 6-week Period

“…Blood samples (3 mL) were collected from the brachial vein in heparinized syringes and centrifuged at 2,500 × g for 10 min to obtain plasma. Plasma samples were used for the determination of plasma NO (nitrate ＋ nitrite) according to Hortelano et al (1995) by adding 250 μl of plasma to 1 mL of Griess reagent. The Griess reagent was a mixture (1:1) of 1% sulfanilamide in 5% phosphoric acid and 0.1% 1-naphthylethylenediamine, giving a red-violet color in presence of nitrite, the stable form of NO.…”