Successful treatment of feline hyperthyroidism often unmasks renal disease. Glomerular filtration rate (GFR) in hyperthyroid cats has been shown to decrease with correction of the hyperthyroid state, often leading to renal insufficiency or failure. Arginine is an essential amino acid in cats and has been shown to have renal protective effects in rats and humans, especially during acute renal crisis. The purpose of this study was to evaluate the potential beneficial effects of arginine supplementation on GFR in hyperthyroid cats treated with radioactive iodine. Twenty-five newly diagnosed hyperthyroid cats undergoing radioactive iodine treatment were enrolled in the study and were randomly assigned to either the supplemented or control group. Each cat had a complete blood count, chemistry profile, urinalysis, total T 4, fT 4ed (free T 4 measured by equilibrium dialysis), and chest radiographs performed, which revealed no disease other than hyperthy roidism. Cats in the supplemented group were given 1.5 g/day of arginine. GFR was assessed by measurement of plasma iohexol clearance (PIC) 2, 3, and 4 hours after injection of 480 mg/kg of iohexol. PIC and plasma arginine levels were measured at 0, 2, and 4 weeks after radioactive iodine treatment. Renal values, T 4, and fT 4ed were measured at 2 and 4 weeks after radioactive iodine treatment. T tests or Mann-Whitney tests were used to evaluate statistical differences. P < .05 was considered significant. Eleven control and nine supplemented cats completed the study. Plasma arginine levels were significantly elevated (P = .0002) in supplemented cats over control cats at 2 weeks (2.8 ± 1.9 and 1.0 ± 0.2 nmol/ml arginine, respectively) and 4 weeks (2.3 ± 0.4 and 1.0 ± 0.13, respectively; P < .0001). Percentage reduction of PIC in the control versus supplemented group was not significant at 2 (0.52 ± 0.98 versus 0.59 ± 0.11; P = .16) or 4 (0.53 ± 0.78 versus 0.58 ± 0.13; P = .26) weeks posttreatment. Arginine supplementation does not demonstrate a protective effect on GFR, as measured by PIC in hyperthyroid cats treated with radioactive iodine.
|Original language||English (US)|
|Number of pages||1|
|Journal||Compendium on Continuing Education for the Practicing Veterinarian|
|Issue number||4 SUPPL.|
|State||Published - Apr 2006|
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