Guanine nucleotide regulation of dopamine receptor agonist affinity states in rat estradiol-induced pituitary tumors.

Abstract

We have investigated dopamine (DA) receptor agonist high- and low-affinity states in female rat estradiol-induced prolactin (PRL)-secreting pituitary tumors and intact pituitary tissue. Estradiol treatment increased the anterior pituitary weight 9-fold and plasma prolactin levels 74-fold and these measures are correlated (R = 0.745, n = 73, p less than 0.001). Competition for [3H]-spiperone binding to the DA receptor by apomorphine was compared in normal and adenomatous pituitary tissue. The inhibition constants (Ki) and the proportions of the two apomorphine sites are unchanged in tumors compared to intact pituitary tissue. Guanosine 5'-[beta-gamma-imino]triphosphate (Gpp(NH)p) causes complete conversion of the high into low affinity dopaminergic agonist site in normal pituitary and in tumors. These results suggest that rats with primary estradiol-induced pituitary tumors have normal and functional DA receptors.

• Authors: T Di Paolo, P Falardeau
• Journal: Life sciences (Life Sci) Vol. 41 Issue 9 Pg. 1149-53 (Aug 31 1987) ISSN: 0024-3205 [Print] Netherlands
• PMID: 3613869 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Guanine Nucleotides
• Receptors, Dopamine
• Guanylyl Imidodiphosphate
• Estradiol
• Prolactin

Topics

• Animals
• Estradiol
• Guanine Nucleotides (physiology)
• Guanylyl Imidodiphosphate (pharmacology)
• Organ Size (drug effects)
• Pituitary Gland, Anterior (anatomy & histology)
• Pituitary Neoplasms (chemically induced, physiopathology)
• Prolactin (metabolism)
• Rats
• Receptors, Dopamine (physiology)