The effect of stanozolol on (15)nitrogen retention in the dog

The objective of the study was to determine the influence of either oral or intramuscular administration of stanozolol on nitrogen retention in dogs b y using a non-invasive N-15-amino acid tracer technique. Ten healthy, intac t, adult male sled dogs received either stanozolol tablets, 2 mg/dog PO, q1 2h, for 25 days (Group 1, n = 5) or an intramuscular injection of 25 mg of stanozolol on Days 7, 14, 21, and 28 (Group 2, n = 5). A N-15 amino acid (5 .27 mmol) was infused intravenously into each dog on Day 0 (before stanozol ol treatment) and on Day 31 (after stanozolol treatment). Urine was collect ed by catheterization from each animal 3 times daily for 3 consecutive days . The N-15-urea enrichment in urine was determined by high-resolution mass spectrometry and the total amount of urea in the urine was determined. Both oral and injectable stanozolol resulted in significant (P < 0.05) increase s in amino acid nitrogen retention compared to pretreatment values. Oral st anozolol increased nitrogen retention from 29.2 +/- 8.2% to 50.3 +/- 9.2%, while stanozolol injection increased nitrogen retention from 26.6 +/- 9.9% to 67.0 +/- 7.5%. The response to intramuscular administration was signific antly greater than the response to the oral dosing regime. Stanozolol incre ases amino acid nitrogen retention in dogs, as has been previously observed in rats. This action of stanozolol may be beneficial in dogs under stress of surgical trauma and chronic disease.