Pertussis toxin-sensitive G-protein mediates the alpha 2-adrenergic receptor inhibition of melatonin release in photoreceptive chick pineal cell cultures
The avian pineal gland is a photoreceptive organ that has been shown to contain postjunctional alpha 2-adrenoceptors that inhibit melatonin synthesis and/or release upon receptor activation. Physiological response and (32P)ADP ribosylation experiments were performed to investigate whether pertussis toxin-sensitive guanine nucleotide-binding proteins (G-proteins) were involved in the transduction of the alpha 2-adrenergic signal. For physiological response studies, the effects of pertussis toxin on melatonin release in dissociated cell cultures exposed to norepinephrine were assessed. Pertussis toxin blocked alpha 2-adrenergic receptor-mediated inhibition in a dose-dependent manner. Pertussis toxin-induced blockade appeared to be noncompetitive. One and 10 ng/ml doses of pertussis toxin partially blocked and a 100 ng/ml dose completely blocked norepinephrine-induced inhibition. Pertussis toxin-catalyzed (32P)ADP ribosylation of G-proteins in chick pineal cell membranes was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Membranes were prepared from cells that had been pretreated with 0, 1, 10, or 100 ng/ml pertussis toxin. In the absence of pertussis toxin pretreatment, two major proteins of 40K and 41K mol wt (Mr) were labeled by (32P)NAD. Pertussis toxin pretreatment of pineal cells abolished (32P) radiolabeling of the 40K Mr G-protein in a dose-dependent manner. The norepinephrine-induced inhibition of both cAMP efflux and melatonin release, as assessed by RIA of medium samples collected before membrane preparation, was also blocked in a dose-dependent manner by pertussis toxin. Collectively, these results suggest that a pertussis toxin-sensitive 40K Mr G-protein labeled by (32P)NAD may be functionally associated with alpha 2-adrenergic signal transduction in chick pineal cells.
- Research Organization:
- Northwestern Univ., Evanston, IL (USA)
- OSTI ID:
- 6840974
- Journal Information:
- Endocrinology; (United States), Journal Name: Endocrinology; (United States) Vol. 123:1; ISSN ENDOA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ADP
AMINES
ANIMALS
ANTIGENS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AUTORADIOGRAPHY
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIRDS
BODY
CELL CULTURES
CHICKENS
DAYS LIVING RADIOISOTOPES
DOSE-RESPONSE RELATIONSHIPS
DRUGS
ELECTROPHORESIS
FOWL
GLANDS
HETEROCYCLIC COMPOUNDS
INDOLES
INHIBITION
ISOTOPES
KINETICS
LIGHT NUCLEI
MATERIALS
MELATONIN
MEMBRANE PROTEINS
MOLECULAR WEIGHT
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PINEAL GLAND
PROTEINS
PYRROLES
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
SECRETION
SYMPATHOMIMETICS
TOXIC MATERIALS
TOXINS
TRYPTAMINES
VERTEBRATES