An evaluation of 5-¹⁴C-delta-aminolevulinic acid as a non-invasive measure of the mixed function oxidase system of mice

The mixed function oxidase system has been postulated as a factor in the development of obesity due to alterations of energy metabolism. Previous measurements of the mixed function oxidase system used an in vitro procedure. A non-invasive measurement of the mixed function oxidase system which would be convenient to use, cause minimal stress to the test subject, and produce consistent results would be desirable.

5-¹⁴-C-delta-aminolevulinic acid was evaluated as a non-invasive measurement of the mixed function oxidase system in mice. ALA (20 mg/ml) was administered by intraperitoneal injections to mice and the 14co excreted via the lungs was collected. A closed circulation apparatus was devised to collect the ¹⁴C0 excreted. The ¹⁴C0 was trapped in a scintillation liquid for radioactive counting by bubbling the gas through a solution of palladium chloride (0.8 g/liter) which converted the ¹⁴CO to ¹⁴C0₂

Two age groups of mice, consisting of six pairs each of obese and lean littermates, were studied. The collection of ¹⁴C0 from the mice was over a three-hour time period 13 to 16 hours after injection of ALA. Immidiately following the ¹⁴C0 collection, the hepatic cytochrome p-450 level of each mouse was determined by isolation of liver microsomes and spectrophotometric examination. The results of the two procedures were compared.

Five normal mice were selected to evaluate the pattern of ¹⁴C0 excretion by collecting ¹⁴C0 at hourly time intervals from 1 through 15 hours after the injection of ALA. . The incorporation of injected ALA into the blood, heart, lungs, kidneys, spleen, and liver of randomly selected groups at eight time periods after injection was also measured. To determine the consequences of an oral dose of ALA, ten rats were administered 4-¹⁴C-ALA on a weight basis. Urine and feces were collected for each rat for 24 hours and then the animal was sacrificed. The incorporation of ALA by the liver, heart, lungs, spleen, and kidneys was measured.

To verify that the ¹⁴C0 collection was a measurement of the mixed function oxidase system, known inducers of the enzyme system were administered to lean mice. Two groups of five mice each received sodium pentobarbital (2mg/ml) for different induction time periods. One group of five mice received injections of benzo-α-pyrene in corn oil (12 mg/ 5 m1). The collected.

Results of this investigation indicated that the administration of ALA and subsequent ¹⁴C0 collection was an effective measure of ¹⁴C0 excretion. The pattern of ¹⁴C0 excretion over a prolonged time period was a sharp initial peak within three hours followed by a steady decline to a stable amount of of ALA incorporation into some of the organs of the mice was noted.

than by obese mice at both ages studied. No difference was noted between the age groups for the lean or the obese mice. It was not possible to

Pentobarbital induction for a sufficient time period resulted in a significantly greater ¹⁴C0 excretion. Benzo-α-pyrene did not appearto cause an increasein the Administration of an oral dose of ALA to rats resulted in a large portion of the ALA being excreted in the urine. However, ALA incorporation into various organs was determined. Differences in incorporation between male and female rat organs were measured.