Unchanged 5′-Deiodinating Activity During the Induction of a Nonthyroidal Illness

Abstract

We investigated the formation of a “nonthyroidal illness” (NTI) in pigs undergoing ventricular fibrillation (VF) and resuscitation. Seven minutes after VF twenty-one pigs received either Epinephrine (E: 45 µg/kg B.W.; n = 7), Norepinephrine (NE: 45 µg/kg B.W.; n = 7), or Vasopressin (VP: 0.8 U/kg B.W.; n = 7). We determined the serum concentrations (sc) of total T₄ (TT₄), FT₄, total T₃ (TT₃) and rT₃ 120 min before, during (t₀), and 5, 15, 60 and 120 min after VF. At the end of the observation period we figured out the in-vitro T₃-generation (k_M, V_max), the in-vitro rT₃-generation, the in-vitro rT₃-decomposition (k_M, V_max) and the content of cytosolic sulfhydryls (total sulfhydryls, non-protein bound sulfhydryls) in liver and kidney specimen. Animals not undergoing VF served as controls (C) for parameters measured in the intracellular compartment. TT₄- and TT₃-sc decreased to 3.3 ± 0.6 µg/dl (p < 0.05, vs. t₀) and 15.2 ± 4.1 ng/dl (p < 0.05, vs t₀), resp. FT₄-sc remained stable for five minutes (2.63 ± 0.41 ng/dl) before declining to 1.8 ± 0.39 ng/dl (p < 0.05, vs. t₀). The rT₃-sc raised finally to 46.9 ± 7.3 ng/dl (p < 0.05, vs t₀). Iodothyronine sc did not exhibit differences between E-, NE- and VP-treatment. Neither in-vitro T₃-generation, nor in-vitro rT₃-generation, nor in-vitro rT₃-decomposition nor intracellular sulfhydryl content were affected by the events of VF and resuscitation as compared to the controls. We therefore conclude that i. A low T₃ high rT₃-syndrome is developed 120 min after VF in pigs; ii. The 5′-deiodination in liver and kidney, which contributes by approximately 60% to circulating T₃ in euthyroid healthy beings, does not account for the alterations of iodothyronine sc within this interval of time.

Key words

Resuscitation - rT₃ - Cardiac Arrest - FT₄ - Non Thyroid Illness - Equilibrium Dialysis - 5′-Deiodination - Vasopressin - 5-Deiodination - Catecholamines