Dihydropyridine-sensitive calcium channel activity related to prolactin, growth hormone, and luteinizing hormone release from anterior pituitary cells in culture: interactions with somatostatin, dopamine, and estrogens
In the present work, we determined the activity of voltage-dependent dihydropyridine (DHP)-sensitive Ca2+ channels related to PRL, GH, and LH secretion in primary cultures of pituitary cells from male or female rats. We investigated their modulation by 17 beta-estradiol (E2) and their involvement in dopamine (DA) and somatostatin (SRIF) inhibition of PRL and GH release. BAY-K-8644 (BAYK), a DHP agonist which increases the opening time of already activated channels, stimulated PRL and GH secretion in a dose-dependent manner. The effect was more pronounced on PRL than on GH release. BAYK-evoked hormone secretion was further amplified by simultaneous application of K+ (30 or 56 mM) to the cell cultures; in parallel, BAYK-induced 45Ca uptake by the cells was potentiated in the presence of depolarizing stimuli. In contrast, BAYK was unable to stimulate LH secretion from male pituitary cells, but it potentiated LHRH- as well as K+-induced LH release; it had only a weak effect on LH secretion from female cell cultures. Basal and BAYK-induced pituitary hormone release were blocked by the Ca2+ channel antagonist nitrendipine. Under no condition did BAYK affect the hydrolysis of phosphoinositides or cAMP formation. Pretreatment of female pituitary cell cultures with E2 (10(-9) M) for 72 h enhanced LH and PRL responses to BAYK, but was ineffective on GH secretion. DA (10(-7) M) inhibited basal and BAYK-induced PRL release from male or female pituitary cells treated or not treated with E2 (10(-9) M). SRIF (10(-9) and 10(-8) M) reversed BAYK-evoked GH release to the same extent in cell cultures derived from male or female animals. It was ineffective on BAYK-induced PRL secretion in the absence of E2, but antagonized it after E2 pretreatment. The effect was dependent upon the time of steroid treatment and was specific, since 17 alpha-estradiol was inactive.
- Research Organization:
- Centre Paul Broca de l'INSERM, Paris (France)
- OSTI ID:
- 6611651
- Journal Information:
- Endocrinology; (United States), Vol. 123:6
- Country of Publication:
- United States
- Language:
- English
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DOPAMINE
BIOCHEMICAL REACTION KINETICS
ESTRADIOL
LH
SECRETION
LTH
PYRIDINES
SOMATOSTATIN
STH
AMP
CALCIUM 45
CELL CULTURES
DOSE-RESPONSE RELATIONSHIPS
ENZYME INHIBITORS
INHIBITION
PHOSPHOLIPIDS
PITUITARY GLAND
PORINS
POTASSIUM
RATS
SEX DEPENDENCE
TRACER TECHNIQUES
ALKALI METALS
ALKALINE EARTH ISOTOPES
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZINES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CARDIOTONICS
CARDIOVASCULAR AGENTS
DAYS LIVING RADIOISOTOPES
DRUGS
ELEMENTS
ENDOCRINE GLANDS
ESTERS
ESTRANES
ESTROGENS
EVEN-ODD NUCLEI
GLANDS
GONADOTROPINS
HETEROCYCLIC COMPOUNDS
HORMONES
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIPIDS
MAMMALS
MEMBRANE PROTEINS
METALS
NEUROREGULATORS
NUCLEI
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANS
PEPTIDE HORMONES
PHENOLS
PITUITARY HORMONES
POLYPHENOLS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RODENTS
STEROID HORMONES
STEROIDS
SYMPATHOMIMETICS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques