Cyanate and Temperature Regulation in Anephric Rabbits (Thermolability).

Abstract

The absence, or lack of functional kidneys is associated with a lowered body temperature. Knochel and Seldin (1976) hypothesized that this reduction is body temperature could be attributable to an increased concentration of cyanate in the plasma of uremic animals. Their hypothesis remained untested since the plasma levels of cyanate were below the measureable limits of all existing assays. To determine whether an increase in the plasma cyanate concentration was responsible for the hypothermia associated with uremia, a sensitive assay was developed to measure plasma concentrations of cyanate. The plasma cyanate concentration was measured in both normal and anephric rabbits; sodium cyanate was then infused into normal rabbits to maintain their plasma cyanate concentration approximately equal to the concentration measured in anephric rabbits (15-20 (mu)M). When this was done in a thermoneutral environment, no change occurred in deep body temperature, suggesting that the above hypothesis be rejected; that is the thermoregulatory set point is not significantly lowered by endogenous cyanate in anephric rabbits. In our initial studies, we found that anephric rabbits not only have lowered thermoregulatory set points, but also are thermolabile, relative to control rabbits. In order to test whether cyanate was responsible for this increase in thermolability, various doses of cyanate were infused into rabbits in either warm or cold environments. Infusion of cyanate into normal rabbits, at a dose that resulted in a fall in body temperature of 1.0(DEGREES)C (resulting in a plasma concentration about 60 times the plasma concentration in anephric rabbits) also makes the animal thermolabile. When the plasma concentration of cyanate in the normal rabbit is raised to that found in anephric rabbits there is a tendency for cyanate-infused normal rabbits to be more thermolabile than saline controls. These data suggest that cyanate, while probably not the sole factor, may contribute to the increase in thermolability found in anephric rabbits. Reference Knochel, J. P. and D. W. Seldin. 1976. The pathophysiology of uremia. In: The Kidney (Brenner and Rector, eds.).