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Alpha 1-Adrenergic Receptors in the Neural Lobe of the Rat Pituitary: Autoradiographic Identification and Localization
  • E. B. De Souza
  • Brian L. Kuyatt, Cedarville University
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α1-Adrenergic receptors were identified, characterized, and localized in rat pituitary gland by quantitative light microscopic autoradiography. Autoradiographic studies were carried out in slide-mounted rat pituitary sections using both [125I]2-[β-(4-hydroxy-3-iodophenyl)ethyl-aminomethyl]tetralone ([125I]HEAT) and [3H]prazosin to localize ai-adrenergic receptors. Data analysis by densitometry showed that [125I] HEAT binding in the rat neural lobe was saturable and of high affinity, with an apparent dissociation constant (Kd) of about 5 pM. Data from competition studies using a variety of compounds demonstrated an α-adrenergic receptor profile for [125I]HEATbinding sites in the rat pituitary. A high density of ai-adrenergic receptors (1 μM prazosin-displaceable [125I]HEAT binding or 10 fiM phentolamine-displaceable [3H]prazosin binding) was found present only in the neural lobe, with negligible concentrations in the anterior and intermediate lobes. The regulation of [126I] HEAT-binding sites in the neural lobe was examined in pituitary stalk-transected and superior cervical ganglionectomized rats. Significant increases in [125I]HEAT-binding sites were observed after superior cervical ganglionectomy, but no changes in [125I] HEAT binding were found in pituitary stalk-transected rats compared to that in sham-operated controls. These data provide the first identification of ai-adrenergic receptors in the neural lobe of the rat pituitary and suggest that these receptors may be localized primarily in blood vessels. In addition, a primary role for the peripheral sympathetic nervous system in regulating the neurohypophyseal vasculature is suggested. The precise function of ai-adrenergic receptors in the neural lobe in regulating posterior lobe hormone secretion remains to be demonstrated.
  • Autoradiography,
  • adrenergic receptors,
  • pituitary gland,
  • rats,
  • neural lobe,
  • posterior lobe,
  • hormone secretion

This work was supported in part by USPHS Grant MH-25951 and a grant from the McKnight Foundation.

PubMed ID
Citation Information
E. B. De Souza and Brian L. Kuyatt. "Alpha 1-Adrenergic Receptors in the Neural Lobe of the Rat Pituitary: Autoradiographic Identification and Localization" Endocrinology Vol. 120 Iss. 6 (1987) p. 2227 - 2233 ISSN: 0013-7227
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