TRH (thyrotropin-releasing hormone) and BAY K 8644 synergistically stimulate prolactin release but not sup 45 Ca sup 2+ uptake

Journal Article · Tue Nov 01 04:00:00 EST 1988 · American Journal of Physiology; (USA)

OSTI ID:6037128

Pachter, J A; Law, G J; Dannies, P S ^[1]

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1. Yale Univ. School of Medicine, New Haven, CT (USA)

Thyrotropin-releasing hormone (TRH) and the Ca{sup 2+}-channel agonist BAY K 8644 each induced transient increases in prolactin secretion from primary cultures of rat anterior pituitary cells in perfusion. When BAY K 8644 was added after a TRH-induced secretory peak, the additional effect of BAY K 8644 on prolactin release was approximately twofold greater over a 30-min period than the effect of BAY K 8644 on previously untreated cells. TRH and BAY K 8644 were also synergistic when added in the opposite order or simultaneously. Substitution of other agents for BAY K 8644 revealed that only high K{sup +} was at least additive with TRH in stimulating prolactin secretion; treatment with TRH inhibited, rather than facilitated, subsequent stimulation of prolactin secretion by angiotensin II or the ionophore A23187. The cooperative effect was not specific for TRH because BAY K 8644 also acted synergistically with angiotensin II or 40 mM K{sup +}. In GH{sub 4}C{sub 1} cells, in which TRH and BAY K 8644 were also synergistic in releasing prolactin, measurements with the fluorescent indicator indo-1 showed that TRH and BAY K 8644 could each elevate cytosolic Ca{sup 2+} above the level stimulated by the other. Unexpectedly, TRH was found to inhibit BAY K 8644-stimulated {sup 45}Ca{sup 2+} uptake in both GH{sub 4}C{sub 1} and primary cultured cells. These results indicate that BAY K 8644 and TRH synergistically stimulate prolactin secretion by a mechanism other than a cooperative effect on the activity of dihydropyridine-sensitive Ca{sup 2+} channels.

• OSTI ID: 6037128
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 255:5; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ANGIOTENSIN
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
CALCIUM 45
CALCIUM ISOTOPES
CARDIOVASCULAR AGENTS
DAYS LIVING RADIOISOTOPES
DRUGS
EVEN-ODD NUCLEI
GLOBULINS
GONADOTROPINS
HORMONES
INTERMEDIATE MASS NUCLEI
ISOTOPES
LTH
NEUROREGULATORS
NUCLEI
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PITUITARY HORMONES
PROTEINS
RADIOISOTOPES
SECRETION
TIME DEPENDENCE
TRH
UPTAKE
VASOCONSTRICTORS