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T P Conway

Publications and source records attributed to T P Conway.

7 recordsLinked to original sources
PubMed1977

Catabolism of rat beta2-microglobulin in the rat.

Highly purified rat beta2-microglobulin (beta2m) as well as cytochrome c and lysozyme were radiolabeled and their catabolism studied in the rat. More than 90 percent of these low molecular weight proteins were removed from the serum within an hour and excreted into the urine by 24 hours. Except for the kidney in which the concentration of these protein is ten- to twentyfold greater than in the serum, there is little evidence that rat tissues are concentrating these proteins. The stomach was found to concentrate radioiodine. The catabolism of rat beta2m differed from that of cytochrome c and lysozyme in that the kidney contained twice as much labeled rat beta2m. In addition, the rat excretes 10 to 15 percent of the injected rat beta2m but only 1 to 5 percent of the cytochrome c or lysozyme. These studies established a basis for turnover studies of beta2m complexed with other cell membrane proteins, for example, HL-A or H-2 peptides.

Animals↗
PubMed1975

Catabolism of photo-oxidized and desialylated hemopexin in the rabbit.

Following injection of rabbit 125I-asialohemopexin, more than 90% of the protein-bound 125I was removed from the circulation of rabbits within 12 min. The amount of asialoprotein in the catabolic compartment reached a peak concentration (75 to 85%) 12 min after injection and was completely eliminated from this compartment within 2 hours. The degradation products were excreted into the urine, with 50 to 70% of the 125I eliminated during the first 24 hours and 90 to 95% excreted by 48 hours. Analysis of these data indicated an apparent first order rate constant for uptake of asialohemopexin of 0.32 min-1, for catabolism of 0.020 min-1 and for excretion of 0.054 to 0.093 hour-1. The plasma distribution curves of 125I-hemopexin, after the first 24 hours, showed essentially no difference. Both proteins were catabolized with an average T1/2 of 25 to 26 hours and a similar fractional catabolic rate. Simultaneous injection of heme and 125I-hemopexin resulted in rapid removal and catabolism of the protein. In contrast, injection of heme had little if any effect on the plasma radioactivity curve of photoinactivated 125I-hemopexin.

Animals↗
PubMed1975

Hemopexin synthesis in vitro by human fetal tissues.

Serum concentrations of hemopexin, transferrin, and albumin were measured for 12 fetuses between 14 and 36 weeks of gestational age. Hemopexin levels ranged from 7 to 64 mug/ml, transferrin levels ranged from 280 to 928 mug/ml, and albumin levels ranged from 13 to 59 mg/ml. In general, the serum concentrations of these three proteins increased with advancing gestation. Placenta, thymus, and colon did not incorporate 14C-labeled amino acids into hemopexin, transferrin, or albumin. By contrast radioimmune precipitates for five culture supernatants of liver indicated significant synthesis of albumin and hemopexin. [14C]Albumin accounted for 22-73% and [14C]hemopexin 1.1-4.2% of the total 14C-labeled proteins. In each instance, the [14C]transferrin was below 1% of the total 14C-labeled proteins.

Amino Acids↗
PubMed1975

Effect of hemoglobin and hematin on plasma clearance of hemopexin, photo-inactivated hemopexin and albumin (38575).

The plasma half clearance time (T1/2) of isotope-labeled rabbit hemopexin was 35.5 plus or minus 1.9 hr in rabbits. After intra-and extra-vascular equilibration of 125I-hemopexin and 131I-albumin, injection of either hematin, hemoglobin or methemoglobin (12.5 mg of heme/kg body wt) resulted in the rapid removal of 60-80% of circulating hemopexin (T1/2 = 7.2 plus or minus 0.6 hr) but did not affect albumin catabolism. After selective photo-inactivation of hemopexin, the T1/2 of this hemopexin was comparable to that of the native molecule. However, its plasma disappearance curve was not appreciably affected by administration of hematin. These findings demonstrate that hemopexin is cleared and catabolized at an enhanced rate during states of plasma heme load, and that modification of critical histidine residues of hemopexin eliminates its biological function in plasma heme disposal.

Animals↗