Clearance Of Hormone Research Articles

The clearance of neurohypophysial hormones from the circulation of non-mammalian vertebrates.

The clearance of neurohypophysial hormones from the circulation of non-mammalian vertebrates.

Effect of iodination on the biological activity and metabolism of human luteinizing hormone.

Studies were performed to estimate the effect of iodine labeling on the biological activity and metabolic clearance of human luteinizing hormone (HLH). Tracer amounts of highly purified 131I-HLH with specific activities of 50–150 μc/μg were mixed with nontracer amounts of human menopausal gonadotropin (HMG) and injected intravenously into 5 monkeys. 131I-HLH was measured by double antibody precipitation and the unlabeled HLH in HMG by radioimmunoassay. The disappearance curves of 131I-HLH and unlabeled HLH were indistinguishable after an initial equilibration period. HMG was iodinated with 127I and assayed by the rat ventral prostate weight assay. There was minimal or no appreciable loss of biological activity, although on some iodinations there appeared to be a slight loss of potency due to the oxidation-reduction procedure. These studies appear to validate the use of 131I-HLH as a metabolic tracer in vivo.

Metabolic clearance and production rates of human luteinizing hormone in pre- and postmenopausal women

Metabolic clearance rates and production rates of human luteinizing hormone (HLH) were determined in pre- and postmenopausal women by the constant infusion technique. Highly purified HLH-(131)I was infused into the fasting subjects at a constant rate. Serial plasma samples were obtained and the radioactive hormone was precipitated by a double antibody technique. Plasma HLH-(131)I levels reached equilibrium by 4 hr after the infusion started. Metabolic clearance rates were: 24.4 +/- 1.8 (mean +/- SE) ml/min in five normal premenopausal women; 23.3 +/- 1.1 ml/min in five normal women taking norethinodrel and mestranol; and 25.6 +/- 4.1 ml/min in four postmenopausal women. Endogenous plasma HLH levels measured in the same subjects by radioimmunoassay immediately before infusion were 32.0 +/- 9.6 mU/ml in the normal women, 16.8 +/- 3.2 mU/ml in the women on oral contraceptives, and 99.2 +/- 23.2 mU/ml in the postmenopausal women. The corresponding HLH production rates were: 734 +/- 170 mU/min in the normal women: 387 +/- 86 mU/min in the women on norethinodrel and mestranol; and 2400 +/- 410 mU/min in the postmenopausal women. The metabolic clearance rate did not change after ovariectomy in one women, but the production rate rose from 583 to 1420 mU/min. Based on previously reported bioassay values for pituitary content and urinary excretion of HLH, the estimated turnover of HLH in the pituitary is about once per day and less than 5% of the total HLH produced appears in the urine in a biologically active form.

The renal clearance of follicle-stimulating and luteinizing hormone in postmenopausal women.

ABSTRACT The renal clearance of follicle-stimulating and luteinizing hormone (FSH, LH) was studied in seven postmenopausal women. The clearance values for FSH ranged from 0.16 to 0.70 (mean 0.58) ml/min, and those for LH from 0.03 to 0.26 (mean 0.14) ml/min. Thus the mean FSH clearance was 4.1 times greater than the LH clearance. The difference was statistically confirmed by the Wilcoxon test. Similarly the mean FSH/LH ratio was four times higher in urine than in plasma when results were expressed in terms of NIH-FSH-S2 and NIH-LH-S3, or in terms of the 2nd International Reference Preparation for Human Menopausal Gonadotrophin. Consequently, the plasma contained relatively more LH than the corresponding urine samples. A nonspecific effect of plasma proteins on the bioassay of FSH and LH was excluded.

Serum binding and biliary clearance of triiodothyronine in cold-acclimated rats.

The more rapid biliary clearance of thyroid hormones resulting from cold acclimation in rats may be the result of an increased capacity of the liver to remove hormone from the blood and (or) to a decreased affinity of the hormone for thyroid-binding protein. The binding of labelled L-triiodothyronine to serum proteins of cold- and warm-acclimated rats has been compared in vitro. Less label was found to bind to protein in sera from cold-acclimated rats, which suggests that a decrease in affinity of thyroid hormones for the binding protein may contribute to the increased biliary clearance found.

BILIARY AND FECAL CLEARANCE OF ENDOGENOUS THYROID HORMONE IN COLD-ACCLIMATED RATS.

The increase in fecal excretion of thyroid hormone by rats as a result of cold acclimation may result from a more rapid biliary excretion of the hormone and/or from a reduction in reabsorption of hormone from the intestinal tract. In the present study cold acclimation was found to increase both biliary and fecal clearances of endogenously labeled hormone. No evidence was found, under the conditions of the experiment, to support the possibility that the greater volume of food eaten in some way reduces reabsorption. Feeding a commercial rat chow led to higher values of both fecal and biliary clearances than feeding a test diet. Significant reabsorption of hormone was not evident. The linear correlation between fecal and biliary clearances indicates the removal of the hormone by the liver and excretion via the bile is the major mechanism governing rate of excretion in the feces.

The metabolism of exogenous and endogenous antidiuretic hormone in the kidney and liver in vivo.

Negligible antidiuretic activity (less than 0.17 mU./g.) was found in extracts of the kidneys either of unanaesthetized adult rats in normal water balance or of rats in whose blood a rise of the level of endogenous antidiuretic hormone had been induced by ether anaesthesia. Extracts of the livers of unanaesthetized rats had negligible antidiuretic activity (less than 0.06 mU./g.), but liver extracts from rats anaesthetized with ether showed antidiuretic effects equivalent to 0.74+/-0.24 mU. Pitressin/g. liver. When Pitressin was injected intravenously into unanaesthetized rats, small amounts of antidiuretic activity were occasionally found in the livers and the kidneys of animals killed up to 3 min. after the injection but none in animals killed later. Some 3% of the antidiuretic activity of an injected dose of Pitressin was found in the urine and the "dead space" of the kidneys in rats decapitated 3 min. after the intravenous injection. When Pitressin was added to rat kidney homogenate and the mixture was incubated at 38 degrees , only 0.75% of the initial antidiuretic activity was recovered after 30 min. and less than 0.40% after 60 min. Experiments with "glomerular" and "tubular" fractions of rat kidney indicated that the inactivation was essentially due to tubular tissue. It is suggested that, in the rat, the kidneys and perhaps the liver are not only sites of clearance of the antidiuretic hormone but also sites of irreversible inactivation.