ABSTRACT
PURPOSE: Lysophosphatidic acid induces neurite retraction; it is also present in tears and aqueous humor. We determined whether lysophosphatidic acid induces HSV-1 reactivation in latently infected rabbits and whether the nerve growth associated protein GAP-43 undergoes posttranslational modification during the course of HSV-1 infection. METHODS: Rabbits were infected with HSV-1 and acute infection was documented by slit lamp examination. Corneas of latently infected rabbits were treated with lysophosphatidic acid or lysophosphatidylserine (structurally similar but lacking biological potency). For application to the cornea, these compounds were impregnated into collagen shields, applied as topical drops, or iontophoresed. In another experiment, corneas of latently infected rabbits were either untreated or treated iontophoretically with lysophosphatidic acid, lysophosphatidylserine, or saline. Ocular swabs detected shedding of infectious virus. Western blot and immunoprecipitation identified GAP-43 in corneal extracts and densitometry of silver-stained isoelectric focusing gels measured changes in GAP-43 isoform abundance. RESULTS: Iontophoresis of lysophosphatidic acid induced HSV-1 shedding more frequently than lysophosphatidylserine or saline. Viral shedding induced by collagen shield and topical drop administration was low and not significantly different for lysophosphatidic acid and lysophosphatidylserine. Five discrete GAP-43 isoforms predominated in the IEF gels. Most abundant were the pI 4.7 band in uninfected cornea and the pI 5.05 band in latently-infected cornea. Compared to latently-infected cornea, there was no significant change in isoform abundance 1 h after lysophosphatidic acid iontophoresis, but 24 and 72 h later, the pI 5. 05 band was diminished. CONCLUSIONS: Lysophosphatidic acid can induce HSV-1 reactivation and changes in GAP-43 pI suggest that posttranslational modifications, possibly related to phosphorylation and ADP-ribosylation, are occurring during HSV-1 latency and after LPA is iontophoretically applied to the cornea. How lysophosphatidic acid-induced signaling, HSV-1 reactivation, and GAP-43 pI are related remains to be determined.
Subject(s)
GAP-43 Protein/metabolism , Herpesvirus 1, Human/growth & development , Lysophospholipids/administration & dosage , Virus Activation/drug effects , Animals , Herpesvirus 1, Human/drug effects , Iontophoresis , Isoelectric Point , Keratitis, Herpetic/metabolism , Keratitis, Herpetic/virology , Lysophospholipids/pharmacology , Protein Isoforms , Protein Processing, Post-Translational , Rabbits , Time Factors , Virus Shedding/drug effectsABSTRACT
The urinary excretion of orotic acid was investigated in four sheep. Nitrogen and energy intake were varied by infusions of urea and glucose. The effect of arginine infusion was also investigated. Nitrogen intake of 10.4 g/d led to a urinary excretion of orotic acid of 357 +/- 61 micrograms/d. Increasing N intake to 21.4 g/d significantly increased urinary orotic acid excretion to 747 +/- 46 micrograms/d. Glucose infusion (300 g/d) significantly decreased orotic acid excretion when N intake was 10.4 g/d, whereas arginine infusion (2.3 g/d) did not alter the excretion of orotic acid under these conditions. When arginine was infused at higher N intake (21.4 g/d), orotic acid excretion decreased from 822 +/- 74 to 624 +/- 46 micrograms/d. It is concluded that increasing N intake is accompanied by an enhanced urinary excretion of orotic acid. This excretion of orotic acid is significantly modified by glucose or arginine.
