Binding and degradation of (/sup 125/I)human growth hormone in rat adipocytes
Iodinated human growth hormone (( /sup 125/I)hGH) binds to both specific and nonspecific sites on the surface of adipocytes isolated from the epididymal fat of normal rats. When adipocytes were incubated at 37 C with 1 nM (/sup 125/I)hGH, specific binding increased for 30-60 min and thereafter remained approximately constant as long as the hormone was present in the medium. About 90% of the /sup 125/I released was soluble in 5% trichloroacetic acid and was in the form of iodotyrosine. The rate of /sup 125/I release from specific binding sites decreased by a factor of 4 when the temperature was lowered from 37 to 17 C. Replacement of some of the sodium chloride in the buffer with 25 mM ammonium chloride had little or no effect on the amount on /sup 125/I that bound to cells when (/sup 125/I)hGH was present in the medium, but completely blocked the release of /sup 125/I from cells transferred to hormone-free medium. Ammonium chloride also significantly reduced both the release of /sup 125/I from nonspecific binding sites and the amount of /sup 125/I recovered in trichloroacetic acid-soluble form. Cloroquine, leupeptin, or colchicine nearly doubled the specific binding of (/sup 125/I)hGH after 180 min and markedly slowed the release of /sup 125/I when cells were transferred to hormone-free medium. All of these agents also significantly reduced the rate of release of /sup 125/I from nonspecific binding sites. Incubation of adipose tissue from hypophysectomized rats with ammonium chloride, leupeptin, or colchicine failed to alter the ability of GH to increase glucose oxidation, induce refractoriness, or promote lipolysis in the presence of theophylline.
- Research Organization:
- Univ. of Massachusetts Medical School, Worcester
- OSTI ID:
- 6202461
- Journal Information:
- Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 115:2; ISSN ENDOA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ALKALOIDS
AMMONIUM CHLORIDES
AMMONIUM COMPOUNDS
AMMONIUM HALIDES
ANIMAL CELLS
ANIMALS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
ANTIMITOTIC DRUGS
ANTIPYRETICS
AROMATICS
AZAARENES
BIOCHEMICAL REACTION KINETICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM DEPRESSANTS
CHLORIDES
CHLORINE COMPOUNDS
COLCHICINE
CONNECTIVE TISSUE CELLS
DRUGS
FAT CELLS
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
HORMONES
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
METABOLISM
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PEPTIDE HORMONES
PITUITARY HORMONES
PURINES
RATS
REACTION KINETICS
RECEPTORS
RESPONSE MODIFYING FACTORS
RODENTS
SOMATIC CELLS
STH
TEMPERATURE DEPENDENCE
THEOPHYLLINE
TRACER TECHNIQUES
VASODILATORS
VERTEBRATES
XANTHINES