[Effect of the Zn supply on alkaline ribonuclease activity in rats]

The purpose of this paper was to show whether the activity of the zinc-dependent enzyme alkaline ribonuclease in zinc-sensitive tissues allows conclusions to be drawn on the Zn supply status. For this 27 weaned male Sprague-Dawley rats were divided into three groups of 9 animals each. A Zn deficiency group, which was given a diet with a Zn content of 3 ppm ad libitum, was compared to a pair-fed and an ad libitum control group with a Zn content in the diet of 60 ppm each. After 22 trial days the animals were killed, and the zinc and protein contents as well as the activity of the alkaline ribonuclease in the serum, testicles, femur, urine, liver, and kidneys were determined. Although the Zn concentration in the serum, testicles, femur, and kidneys of the deficiency animals were significantly reduced, the alkaline ribonuclease showed an increased activity only in the kidneys, in the testicles the activity was reduced, and in the serum, femur, urine and liver it remained unchanged. The protein concentration in serum and femur was reduced because of Zn deficiency, whereas the decrease in testicles, liver and kidneys must be attributed to the reduced feed intake. The influence of the dietary Zn deficiency on the activity of the alkaline ribonuclease was therefore more the result of an altered feed intake and growth rate than a direct effect of zinc on the enzymatic system. Therefore the determination of the activity of the alkaline ribonuclease can be excluded as a parameter for the diagnosis of Zn supply and Zn deficiency.