Professor Universidade Federal do Rio Grande do Sul Porto Alegre, Rio Grande do Sul, Brazil
Abstract: Background – Equivalence between 5 µg/kg and 125 µg/cat doses in the ACTH stimulation test (AST) was documented in cats regarding different synthetic corticotropins such as tetracosactide and cosyntropin.
Hypothesis/Objectives – assess the dose-equivalence for the AST between 1 or 5 µg/kg against the 125 µg/cat dose of a commercial product with recombinant porcine corticotropin (ACTHEL 25UI).
Animals – Seven healthy neutered cats (four males) from a shelter.
Methods – Cross-sectional study. Intravenous ACTHEL injections of 1 µg/kg, 5 µg/kg, and 125 µg/cat with a seven-day interval for each test were applied in each cat. Blood samples were drawn before and one hour after ACTHEL for aldosterone, cortisol, and progesterone measurements by radioimmunoassay and androstenedione by chemiluminescent assay. Pre- and post-ACTH results were compared by the Wilcoxon matched-pairs test. The Δ-hormonal for each dose tested was compared by Friedman´s test followed by Dunn´s test.
Results – Androstenedione concentration was not stimulated for any tested dose. A significant (p=0.03) increase in post-ACTH progesterone with 1 µg/kg was observed. The 5 µg/kg dose promoted increases in post-ACTH aldosterone (p=0.01) and progesterone (p=0.01). The 125 µg/cat dose promoted a significant increase (p=0.01) in post-ACTH aldosterone, cortisol, and progesterone serum concentration. The 125 µg/cat dose showed higher Δ-hormonal for aldosterone (p=0.003), cortisol (0.008), and progesterone (p=0.05).
Conclusions and clinical importance – The reduced doses tested were considered inappropriate to assess cortisol adrenal reserve in the AST; notwithstanding, they were capable of significantly increasing progesterone (1 and 5 µg/kg) and aldosterone (5 µg/kg) serum concentration.
