Concomitant inhibition of pulsatile luteinizing hormone (LH) and stimulation of prolactin release by prostacyclin (PGI/sub 2/) in ovariectomized (OVX) conscious rats
Prostacyclin (PGI/sub 2/) or its stable metabolite, 6-keto-PGF/sub 1 alpha/ in 2.5 ..mu..l 0.05 M phosphate buffer, was injected into the third ventricle (3 V) of ovariectomized (OVX), freely moving rats. Control animals received 2.5 ..mu..l of buffer. In the initial experiments a control blood sample was taken and then the PGI/sub 2/ was injected and frequent samples taken thereafter. With this protocol injection of 2 ..mu..g of PGI/sub 2/ produced a significant decrease in mean plasma LH only at 60 min after its injection, while the higher dose decreased plasma LH concentration at 30 and 60 min. In subsequent experiments, blood was removed from indwelling external jugular vein cannulae every 5-6 min during 2 hours and plasma LH and PRL levels were determined by radioimmunoassay. LH pulses were monitored and several parameters of LH pulsation were calculated during the hour before and after injection of phosphate buffer, PGI/sub 2/ or 6-keto-PGF/sub 1a/. Intraventricular injection of phosphate buffer failed to modify the characteristic pulsatile release of LH and did not alter plasma PRL levels. The amplitude of LH pulses was significantly reduced by PGI/sub 2/ and the inhibitory effect was dose-related. Even a dose of 1 ..mu..g produced a significant reduction in pulse height and the response was graded with maximal reduction occurring with the 5 ..mu..g dose which essentially abolished the LH pulses.
- Research Organization:
- Univ. of Texas Health Science Center, Tyler (USA)
- OSTI ID:
- 5983123
- Journal Information:
- Life Sci.; (United States), Vol. 43:25
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LH
BIOSYNTHESIS
LTH
SECRETION
PROSTAGLANDINS
BIOCHEMICAL REACTION KINETICS
BLOOD PLASMA
BUFFERS
DOSE-RESPONSE RELATIONSHIPS
INHIBITION
RADIOIMMUNOASSAY
RATS
ANIMALS
BIOLOGICAL MATERIALS
BLOOD
BODY FLUIDS
GONADOTROPINS
HORMONES
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
KINETICS
MAMMALS
MATERIALS
PEPTIDE HORMONES
PITUITARY HORMONES
RADIOASSAY
RADIOIMMUNOLOGY
REACTION KINETICS
RODENTS
SYNTHESIS
TRACER TECHNIQUES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques