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PROLACTIN RECEPTORS: CHARACTERISTICS OF THE PARTICULATE FRACTION BINDING ACTIVITY

PROLACTIN RECEPTORS: CHARACTERISTICS OF THE PARTICULATE FRACTION BINDING ACTIVITY SUMMARYOvine 125I-labelled prolactin was incubated with a membrane-rich particulate fraction of mouse mammary gland and bound hormone was separated by centrifugation and washing. The experiments identified two types of binding activity: total binding and specific binding, the fraction of the total which could be displaced competitively by native prolactin but not by a number of other polypeptides. Two other lactogenic hormones, human chorionic somato-mammotrophin and human growth hormone, displaced 125I-labelled prolactin in proportion to their known intrinsic lactogenic activities. Binding of 125I-labelled prolactin was complete within 20 min at 4 or 37 °C. Scatchard analysis of the binding indicated an apparent dissociation constant (Kd) of approximately 9 × 10−9 mol/l and a concentration of binding sites of 15·5 × 10−13 mol/mg particulate protein. The greatest rate of specific displacement of bound 125I-labelled prolactin was observed at concentrations of prolactin between 50 and 250 ng/ml, a concentration range near the mid-point of the dose—response curve of casein induction in intact mammary cells. The saturating concentration of prolactin for specific binding to mammary particles was similar to that for casein induction in intact cells. The prolactin binding activity was sensitive to treatment with trypsin or heating at 70 °C, indicating its protein nature. These properties of the mammary prolactin binding activity are those required of a receptor for prolactin or other lactogens. Prolactin-specific binding activity was also found in particles from mouse liver, kidney, and midbrain and from the ovary, adrenal, and seminal vesicle of the rat. These results suggest a fairly widespread tissue distribution of the prolactin receptor, and potentially implicate prolactin in the hormonal regulation of these organs. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Endocrinology Bioscientifica

PROLACTIN RECEPTORS: CHARACTERISTICS OF THE PARTICULATE FRACTION BINDING ACTIVITY

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Publisher
Bioscientifica
Copyright
Copyright © 1974 The Authors. All Rights Reserved.
ISSN
0022-0795
eISSN
1479-6805
DOI
10.1677/joe.0.0600485
Publisher site
See Article on Publisher Site

Abstract

SUMMARYOvine 125I-labelled prolactin was incubated with a membrane-rich particulate fraction of mouse mammary gland and bound hormone was separated by centrifugation and washing. The experiments identified two types of binding activity: total binding and specific binding, the fraction of the total which could be displaced competitively by native prolactin but not by a number of other polypeptides. Two other lactogenic hormones, human chorionic somato-mammotrophin and human growth hormone, displaced 125I-labelled prolactin in proportion to their known intrinsic lactogenic activities. Binding of 125I-labelled prolactin was complete within 20 min at 4 or 37 °C. Scatchard analysis of the binding indicated an apparent dissociation constant (Kd) of approximately 9 × 10−9 mol/l and a concentration of binding sites of 15·5 × 10−13 mol/mg particulate protein. The greatest rate of specific displacement of bound 125I-labelled prolactin was observed at concentrations of prolactin between 50 and 250 ng/ml, a concentration range near the mid-point of the dose—response curve of casein induction in intact mammary cells. The saturating concentration of prolactin for specific binding to mammary particles was similar to that for casein induction in intact cells. The prolactin binding activity was sensitive to treatment with trypsin or heating at 70 °C, indicating its protein nature. These properties of the mammary prolactin binding activity are those required of a receptor for prolactin or other lactogens. Prolactin-specific binding activity was also found in particles from mouse liver, kidney, and midbrain and from the ovary, adrenal, and seminal vesicle of the rat. These results suggest a fairly widespread tissue distribution of the prolactin receptor, and potentially implicate prolactin in the hormonal regulation of these organs.

Journal

Journal of Endocrinology – Bioscientifica

Published: Mar 1, 1974

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