[The radioprotective effect of iodine and its preventive action on renal calcification (author's transl)]. / Der Strahlenschutzeffekt des Jods und seine kalzifikationsverhindernde Wirkung auf die Nieren.

The protective effect of iodine against injurious damage caused by ionizing radiation was studied in 26 rats irradiated with cobalt-60 gamma rays as a single dose of 1000 rads (10 joule/kg). Twelve rats were pretreated 13 times every second day before irradiation. After irradiation they were treated daily during 21 days with 2.5 to 3.0 mg iodine given subcutaneously along with 9 mg Ca2+ (as gluconolactobionate) intramuscularly. In addition, they received 500 micrograms of iodine in their food daily. 67% of the iodine-treated rats remained alive after 30 days in contrast to 36% of the control rats which received Ca2+ only. 10 further rats which received neither iodine nor Ca2+ died within 3 to 5 days after irradiation. Deposition of calcium in the renal parenchyma was observed in 12 out of the 14 control rats, but only in 2 out of the 12 iodine-treated rats. It can be concluded from the results that iodine has a protective effect on ionizing radiation. It is assumed that iodine promotes the energy-conserving mechanism in mitochondria and also prevents the irradiation-induced decrease in calcium efflux.

Clofibrate-induced increase in coenzyme A concentration in rat tissues.

1. When clofibrate [ethyl 2-(4-chlorophenoxy)-2-methylpropionate] was administered subcutaneously to rats (600mg/kg per day for 5 days), the concentration of CoA and its acyl derivatives increased in several tissues. The increase in total CoA was 3.2-fold in the liver, 1.8-fold in the kidney, 2.7-fold in the heart and 2.4-fold in skeletal muscle. 2. To study the mechanism of this phenomenon, clofibrate-treated rats were injected with [(3)H]pantothenate intracardially and killed after 15min, 30min, 1 and 2h and 1, 3, 5 and 7 days for the determination of the incorporation of radioactivity into CoA and its precursors. Incorporation into CoA after 2h was 6.2-fold in the liver as compared with the control values and 4.6-fold in the kidneys. 3. The disappearance of the label from CoA was very slow compared with the rate of incorporation; it exhibited exponential kinetics, and was slower in the livers of the clofibrate-treated rats (t((1/2)) 18.2 days) than in the controls (t((1/2)) 5.6 days). 4. The rate of CoA degradation, calculated from the calculated rate constants of the apparent first-order kinetics of the disappearance of the label and from the CoA pool sizes, was approximately the same in the clofibrate-treated animals (11.5pmol/min per g), and the controls (11.6pmol/min per g). 5. These rates of CoA degradation indicate that the effect of clofibrate on CoA concentration may be mainly due to inhibition of the enzymes of CoA degradation, although recycling of the label cannot be excluded. The increase in the rate of pantothenate incorporation into CoA suggests that clofibrate also increases the synthesis of CoA.

Oxidation-reduction midpoint potentials of mitochondrial flavoproteins and their intramitochondrial localization.

Spectrophotometric and fluorimetric substrate couple titrations and potentiometric spectrophotometric titrations were used to determine the oxidation-reduction potentials of components showing absorbance or fluorescence at the wavelengths attributable to the flavoproteins of mitochondria fractionated using digitonin together with sonication. A pure mitoplast fraction devoid of cytochrome b5 contamination could be obtained using 230 micrograms digitonin/mg of mitochondrial protein. The digitonin-soluble fraction contained a species having Em7.4 = -123 mV and probably represents the outer membrane flavoproteins. The inner membrane-matrix fraction, treated with ultrasound, provided evidence of a flavoprotein species with redox potential (Em7.4 = -302 mV) in the matrix fraction. The -302 mV component is probably lipoamide dehydrogenase. A high redox potential species with Em7.4 = +19 mV in titrations with the succinate fumarate couple was located in the inner membrane vesicles and is probably identical with succinate dehydrogenase. The electron-transferring flavoprotein (ETF) was isolated from bovine heart mitochondria and its Em7.4 = -74 mV determined. The component in the matrix fraction with an apparent Em7.4 = -56 mV probably represents ETF, and that in the inner membrane fraction with an apparent Em7.4 = -43 mV the NADH dehydrogenase flavoprotein. A component in an apparently low concentration with Em7.4 = +30 mV was detected in the inner membrane fraction. This probably represents the ETF-dehydrogenase flavoprotein. The origin of the flavoprotein fluorescence of mitochondria and intact tissues is discussed.