Biomedical subjects

D S Gaydos

Publications and source records attributed to D S Gaydos.

3 recordsLinked to original sources

PubMed1983

The regulation of renal ammoniagenesis in the rat by extracellular factors. III. Effects of various fuels on in vitro ammoniagenesis.

The addition of many oxidizable substrates to the medium of incubating rat renal slices decreases ammoniagenesis from glutamine and glutamate. Interestingly, lactate and beta-hydroxybutyrate depress ammoniagenesis less in renal slices from acidotic rats compared with normal-control rats. In this study, the effects of an expanded panel of substrates on ammoniagenesis in kidney slices from control and acidotic rats were followed to discern patterns of inhibition. In addition to lactate and beta-hydroxybutyrate, acetate, pyruvate, and perhaps acetoacetate caused relatively less depression of ammoniagenesis in acidotic slices. Citrate, succinate, fumarate, octanoate, and alpha-ketoglutarate decreased ammoniagenesis to the same extent or more in acidotic slices compared with that in normal-control slices. Glycerol had little effect on ammoniagenesis under either condition. From the substrates tested, it can be generalized that those outside the TCA cycle (with exception of octanoate) depress ammoniagenesis less during acidosis, while those in the TCA cycle depress ammoniagenesis equally or even more during acidosis. We hypothesize from the pattern of our results that changes in renal intermediary metabolism at or before citrate formation occur during acidosis and are important regulatory mechanisms for ammoniagenesis.

3-Hydroxybutyric Acid↗

PubMed1983

Partial characterization of a renotropic factor.

In 70 experiments, the existence of a circulating renal growth factor was confirmed by 9.3% stimulation of 3H-thymidine into the DNA of renal fragments incubating for 90 min in the presence of sera from 20-hour unilaterally nephrectomized rats compared to sera from 20-hour sham-operated rats (p less than 0.001). Dialysis (7.4%, p less than 0.01) or removal of albumin (11.8%, p less than 0.001) from sera of both sham-operated and unilaterally nephrectomized rats did not appreciably change the magnitude of the statistically significant stimulation. When albumin-free sera were placed in boiling water for 1-3 min to coagulate protein, the stimulation was still significantly different from control (5%, p less than 0.05). Addition of sera from unilaterally nephrectomized rats (20 h) to isolated nuclei, even isolated nuclei removed from growing kidneys (72 h after unilateral nephroctomy), failed to enhance DNA synthesis significantly.

Animals↗

PubMed1981

Correlation between glutamate deamination and glutamine deamidation in rat kidney mitochondria.

Intramitochondrial glutamate removal through deamination may regulate renal ammoniagenesis from glutamine. However, little information is available to determine if there is a strong association between glutamine deamidation and the removal within mitochondria of the glutamate subsequently formed after deamidation. Using rat renal mitochondria, we found that ammonia production, glutamate appearance, and amide nitrogen disappearance were near equal aerobically and anerobically, when no ADP-generating system was present. When an ADP-generating system was added (ATP alone, ATP+ malonate, or ATP+2,4 DNP), more ammonia was formed aerobically from glutamine. Additionally, less glutamate appeared even though more amide nitrogen disappeared. Intramitochondrial concentrations of glutamate decreased. When pyruvate and alpha-ketoglutarate were added to the system, ammoniagenesis, deamidation, and deamination decreased; while glutamate built up in both the medium and mitochondria. In our mitochondrial system, we found a significantly positive correlation between glutamate deamination and glutamine deamidation, between glutamate accumulation and intramitochondrial glutamate concentrations; and a significantly negative correlation between glutamate deamination and glutamate accumulation, between glutamine deamidation and intramitochondrial glutamate concentrations, and between glutamate deamination and glutamate accumulation. We conclude that there is a biochemical relationship between glutamine deamidation and deamination of the glutamate subsequently formed. We propose that increased deamination lowers mitochondrial concentrations of glutamate and increases deamidation. In contrast, slowing deamination increases mitochondrial concentrations of glutamate and decreases deamidation.

Adenosine Diphosphate↗