Metabolic clearance rate and urinary clearance of purified beta-core
- National Institute of Child Health and Human Development, Bethesda, MD (USA)
We injected a highly purified preparation of the beta-core molecule, a fragment of hCG beta excreted in pregnancy urine, into five men and three women to determine its kinetic parameters, MCR, and urinary clearance. The beta-core molecule was distributed in an initial volume (1950 +/- 156 (mean +/- SEM) mL/m2 body surface area) approximately equal to the estimated plasma volume. Its disappearance was multiexponential on a semilogarithmic plot, with a rapid phase t1/2 of 3.5 +/- 0.7 min and a slow phase t1/2 of 22.4 +/- 4.2 min. The transit time (the mean time spent by a molecule of beta-core in transit) was 20.6 +/- 2.1 min. The MCR was 192.0 +/- 8.0 mL/min.m2 body surface area. About 5% of the injected dose of beta-core was excreted into the urine in the first 30 min after injection, and low levels of excretion persisted for up to 7 days. The urinary clearance rate of beta-core was 13.7 +/- 1.4 mL/min.m2, accounting for about 8% of the elimination of beta-core from the plasma. The beta-core immunoreactivity in serum and urine was characterized by gel filtration and three independent RIA systems to show that its properties were indistinguishable from those of the injected beta-core. Serum levels of beta-core in pregnant women were less than 0.2 ng/mL, while the amounts excreted in their urine were as much as 5 mg/day. Based on these clearance parameters of beta-core in normal subjects, less than 0.2% of the beta-core excreted in pregnancy urine is derived by urinary clearance of plasma beta-core. Therefore, more than 99% of the beta-core excreted in pregnancy urine is derived from beta-core in a compartment separate from plasma. In particular, these data indicate that there is relatively little placental secretion of beta-core into plasma and that placental secretion does not account for the vast majority of beta-core in pregnancy urine.
- OSTI ID:
- 5546470
- Journal Information:
- Journal of Clinical Endocrinology and Metabolism; (USA), Vol. 69:3; ISSN 0021-972X
- Country of Publication:
- United States
- Language:
- English
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GONADOTROPINS
METABOLISM
CHROMATOGRAPHY
CLEARANCE
MAN
MENSTRUAL CYCLE
PREGNANCY
RADIOIMMUNOASSAY
ANIMALS
BIOASSAY
DIAGNOSTIC TECHNIQUES
HORMONES
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
MAMMALS
PEPTIDE HORMONES
PITUITARY HORMONES
PRIMATES
RADIOASSAY
RADIOIMMUNODETECTION
RADIOIMMUNOLOGY
SEPARATION PROCESSES
TRACER TECHNIQUES
VERTEBRATES
550501* - Metabolism- Tracer Techniques