Grass Carp (Ctenopharyngodon idellus) Bile may Inhibit the Release of Renal Dipeptidase from the Proximal Tubules by Nitric Oxide Generation

Abstract

There are many reports on acute renal failure (ARF) after ingestion of grass carp bile (CB; Ctenopharyngodon idellus). Renal dipeptidase (RDPase; EC 3.4.13.19) is a glycosylphosphatidylinositol–anchored ectoenzyme within the renal proximal tubules (PTs) and is proposed as a diagnostic enzyme of renal disease. We examined the release of RDPase following treatment with CB and various nitric oxide (NO) related compounds in porcine PTs. The RDPase release from PTs was inhibited by CB in a concentration–dependent manner and was also inhibited by sodium nitroprusside (direct NO donor) and L–arginine (NO synthase substrate) in the tested range (0–12 mM). CB–treated (0.1 mg/ml) PTs showed a decreased RDPase activity in comparison with the control group. This inhibition was blocked by 2 mM L–NAME (NO synthase inhibitor) and U73122 (inhibitor of phosphatidylinositol–specific phospholipase C) in a concentration–dependent manner. Eel bile (0–0.1 mg/ml), used as the control, did not significantly affect the RDPase release from PTs. The NO concentration was observed as nitrite, the degradation product of the NO metabolism, increased in proportion to CB and L–arginine. The increase of nitrite to 151.5% by CB treatment (0.1 mg/ml) was blocked by 2 mM L–NAME (95.5%). When the phospholipase C pathway was blocked by 10 and 20 μM U73122, the nitrite generation decreased to 122.7 and 89.4%, respectively. These results strongly suggest that NO generation and the phospholipase C pathway affect the RDPase release from the PTs and that they may be involved in the development of ARF in vivo following CB ingestion. The release of RDPase from PTs could be a useful tool not only for this CB–caused ARF, but also for the elucidation of other biochemical mechanisms.

Nitric oxide inhibits the shedding of the glycosylphosphatidylinositol-anchored dipeptidase from porcine renal proximal tubules

“…correlate well with our previous observations that carp bile led to the generation of NO via an intracellular PI-PLC [22].…”

“…The reciprocal correlation between RDPase release and nitrite concentration is demonstrated by the crossingover of the two lines as shown in Figure 2(A). Half-maximal inhibition of RDPase release was observed at an -Arg concentration of 8.7 mM, which corresponds to a nitrite concentration of 1.8 nmol\mg of protein, similar to the result obtained previously with carp bile [22]. These data are in good agreement with the results in Figure 1 where the direct donors of NO (SNP and SNAP) inhibited the release of RDPase from the proximal tubules.…”

“…The underlying mechanism for the shedding of the GPI-anchored RDPase from the membrane of the kidney proximal tubules involves an endogenous GPI-PLC based on the identification of the inositol-1,2-cyclic monophosphate CRD on both RDPase released in itro [23] and on the protein in the urine of pigs and humans in i o [24]. A reduction in the release of RDPase from porcine proximal tubules treated with carp bile, which is known to cause acute renal failure, has been shown to be caused by NO generation, although the reduction was not observed with eel bile [22]. These observations correlate with reports that NO is elevated in conditions of renal disease [7,8,17].…”

“…In our in itro system of porcine proximal tubules, carp bile (from Ctenopharyngodon idellus), which causes acute renal failure [20,21], produced NO and simultaneously decreased the release of the glycosylphosphatidylinositol (GPI)-anchored renal dipeptidase (RDPase ; also known as membrane dipeptidase and dehydropeptidase I ; EC 3.4. 13.19) [22]. These observations raise the possibility that NO may play an important role in suppressing the shedding of RDPase, as well as in the inflammation and apoptosis of proximal tubules, through certain signal-transduction mechanisms.…”

Intracellular Calcium Involvement in Pituitary Adenylate Cyclase‐Activating Polypeptide Stimulation of Growth Hormone and Gonadotrophin Secretion in Goldfish Pituitary Cells

“…U73122 has been shown to inhibit IP 3 formation from PIP 2 at the low micromolar range (35). In this study, we chose to use a drug concentration of 10 µ M , which has been shown to be effective in studies involving a related cyprinid, the grass carp (36). Application of U73122 caused a slow but continuous increase in basal GH release that eventually reached a huge magnitude (Fig.…”