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L C Costello

Publications and source records attributed to L C Costello.

At least 73 records · Page 4Linked to original sources
PubMed1978

Citrate and isocitrate utilization by rat ventral prostate mitochondria.

Isolated rat ventral prostate mitochondria preparations were capable of utilizing exogenous isocitrate with some resulting production of citrate. The prostate preparation did not utilize citrate or alphaKG. Citrate utilization via isocitrate seems to be limited by a unique aconitase activity which permits isocitrate to citrate but not citrate to isocitrate conversion. In contrast, kidney cortex mitochondria (under these same conditions) were capable of utilizing citrate, isocitrate, and alphaKG, and also converting isocitrate to citrate. The results support the view that citrate oxidation by prostate may be limited at the aconitase step, and thus may be a key step in accounting for the uniquely high citrate content of prostate.

Animals↗
PubMed1978

Isocitrate uptake and citrate production by rat ventral prostate fragments.

Prostatic aconitase was investigated utilizing fragments of rat ventral prostate. The rate of citrate formation from isocitrate was used as an index of aconitase activity. Inhibition of citrate formation from isocitrate by fluorocitrate indicated that aconitase activity was being measured. The results indicated that whereas both kidney and prostate formed citrate from isocitrate, the aconitase activity of prostate was independent of both medium isocitrate and citrate concentration. In addition the aconitase activity of prostate seemed to favor citrate formation to a much greater degree than kidney. The results showed that the aconitase catalyzed conversion of citrate to isocitrate is limited in prostate and suggested that the deficient citrate oxidation observed in prostate is the result of a unique aconitase activity.

Aconitate Hydratase↗
PubMed1977

Citrate uptake and oxidation by fragments of rat ventral prostate.

Citrate oxidation was studied utilizing an in vitro preparation of rat ventral prostate which was very similar, with respect to citrate metabolish, to the intact prostate. The rate of citrate oxidation was very slow in comparison to kidney, although citrate entered prostatic tissue and accumulated intracellularly. Citrate was converted to isocitrate at a rate which resulted in a constant citrate/isocitrate ratio over a 10-fold variation in medium citrate concentration. The prostate oxidized significantly more alpha-ketoglutarate and malate than citrate. These results suggested that limited citrate oxidation could account for the accumulation of high prostatic citrate levels.

Animals↗
PubMed1976

RENAL HANDLING OF CITRATE DURING HEAT-INDUCED HYPOCITRICEMIA.

A model of steady-state hypocitricemia, characterized by hypocitraturia and reduced kidney cortex citrate, has been demonstrated in the rate chronically exposed to environmental heat. The renal citrate extraction ratio remains unchanged. The physiological mechanism that brings about the reduction in circulating citrate has not been determined. Hypocitraturia likely results from a decreased filtered citrate load. Although it is generally contended that filtered citrate load. Although it is generally contended that alkalosis increases and acidosis decreases renal excretion of citrate, observations of mild alkalosis and hypocitraturia during heat exposure suggest that factors other than pH can alter renal handling of citrate. Kidney mitochondrial function, as determined by in vitro measurements of citrate-stimulated respiratory rates and specific activities of isocitrate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, and cytochrome c oxidase, appears to be unaffected by environmental heat.

Animals↗
PubMed1976

Mitochondrial isocitrate dehydrogenase and isocitrate oxidation of rat ventral prostate.

Mitochondrial preparations isolated from rat ventral prostate were capable of oxidizing isocitrate by way of NADP isocitrate dehydrogenase (NADP-IDH) and NAD-IDH. NAD-IDH activity required ADP for activation. The pH responses for NAD-IDH and NADP-IDH were quite different. The results indicated that two different enzymes were involved in the NAD- and NADP-IDH activities. Indirect evidence indicated that NADPH-NAD transhydrogenase activity might also be involved in the mitochondrial pathway for isocitrate oxidation. NADP-IDH activity was significantly greater than NAD-IDH activity. The oxidation of isocitrate through IDH activity was coupled to the cytochrome system by NADPH- and NADH-cytochrome c reductase activities. Citrate, via isocitrate, oxidation proceeded at a much slower rate suggesting that aconitase activity could be limiting in the oxidation of citrate. In comparison to other tissues, the prostate oxidative enzyme activities are considerably lower. The results suggest that the accumulation of high prostate citrate levels is not due to a limitation imposed by a lack of IDH activity in prostate mitochondria.

Animals↗
PubMed1975

Effects of semistarvation on rat liver, kidney, and heart mitochondrial function.

Two groups of rats were provided simultaneously with a commercial stock diet for a period of 7 days. One group was fed ad libitum (control), and the other was restricted to one-fourth of the daily intake of control animals (semistarved). Body weight declined significantly in semistarved rats whereas body weight of controls increased over the 7-day period. The following were determined in vitro on mitochondria isolated from liver, kidney, and heart tissues of both groups: substrate-stimulated and DNP-uncoupled respiratory rates; specific acivities of the Krebs cycle dehydrogenases, and cytochrome c oxidase. Degradative effects of reduced food intake on mitochondrial function were observed. Uncoupled respiratory rates of liver and kidney mitochondria (using succinate as substrate) and heart mitochondria (using alpha-ketoglutarate and pyruvate) were lower. Also lower were activities of isocitrate dehydrogenase, NADP: isocitrate dehydrogenases, transhydrogenase, succinate dehydrogenase, and cytochrome c oxidase of heart mitochondria, transhdrogenase of liver mitochondria, and isocitrate dehydrogenase and transhydrogenase of kidney mitochondria. Such decreases in enzyme activities under conditions of dietary protein deficiency might have their basis in breakdown rates exceeding synthesis rates or result from partial inactivation of existing enzyme protein. Thus, there is evidence that responses to semistarvation of such parameters of mitochondrial function may differ among various tissues. In addition, liver and kidney citrate levels were lower and heart citrate level higher with semistarvation.

Animal Nutritional Physiological Phenomena↗