Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Transforming growth factor-α: receptor binding and action on DNA synthesis in the sheep mammary gland

Transforming growth factor-α: receptor binding and action on DNA synthesis in the sheep mammary... AbstractMicrosome fractions prepared from the mammary glands of non-pregnant, pregnant and lactating sheep have been used to study binding of 125I-labelled transforming growth factor-α (TGF-α). Binding was dependent on microsomal protein concentration, time and temperature. It showed the characteristics of an epidermal growth factor (EGF) receptor, being displaced by TGF-α and EGF, but not by insulin or IGF-I. The non-linear curve fitting program LIGAND was used to determine affinity and number of binding sites. A single class of high-affinity binding sites was found. The apparent dissociation constant (Kd) was similar in all physiological states (2·43±0·27 mol/l × 10−10, n=23). Numbers of binding sites were lower in late-pregnant (20 weeks) and lactating sheep (14·07± 2·45 fmol/mg protein, n=10) than in non-pregnant, 10-or 15-week pregnant sheep (43·04±5·93 fmol/mg protein, n=13).DNA synthesis by mammary alveolar epithelial cells cultured on collagen gels was increased twofold by TGF-a (maximum response at 10 μg/l; 1·8 nmol/l) but not by EGF. Cells derived from 15- to 20-week pregnant sheep responded significantly to TGF-α on day 3 of culture, but the response was delayed to day 4–5 of culture in cells from other physiological states. Dose–response was not significantly affected. TGF-α and IGF-I produced an additive effect on DNA synthesis. Oestradiol (10−12 to 10−9 m), a potential stimulator of the TGF-α gene, did not stimulate DNA synthesis alone, or in combination with IGF-I. It is concluded that growth factors acting via the EGF receptor play a role in ruminant mammary development, but whether they mediate oestradiol effects remains unresolved.Journal of Endocrinology (1995) 144, 165–171 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Endocrinology Bioscientifica

Transforming growth factor-α: receptor binding and action on DNA synthesis in the sheep mammary gland

Moorby, C D; Taylor, J A; Forsyth, I A
Journal of Endocrinology , Volume 144 (1) – Jan 1, 1995
Download PDF
7 pages

Loading next page...
 
/lp/bioscientifica/transforming-growth-factor-receptor-binding-and-action-on-dna-CT00d346T9

References

References for this paper are not available at this time. We will be adding them shortly, thank you for your patience.

Publisher
Bioscientifica
Copyright
Copyright © 1995 The Authors. All Rights Reserved.
ISSN
0022-0795
eISSN
1479-6805
DOI
10.1677/joe.0.1440165
Publisher site
See Article on Publisher Site

Abstract

AbstractMicrosome fractions prepared from the mammary glands of non-pregnant, pregnant and lactating sheep have been used to study binding of 125I-labelled transforming growth factor-α (TGF-α). Binding was dependent on microsomal protein concentration, time and temperature. It showed the characteristics of an epidermal growth factor (EGF) receptor, being displaced by TGF-α and EGF, but not by insulin or IGF-I. The non-linear curve fitting program LIGAND was used to determine affinity and number of binding sites. A single class of high-affinity binding sites was found. The apparent dissociation constant (Kd) was similar in all physiological states (2·43±0·27 mol/l × 10−10, n=23). Numbers of binding sites were lower in late-pregnant (20 weeks) and lactating sheep (14·07± 2·45 fmol/mg protein, n=10) than in non-pregnant, 10-or 15-week pregnant sheep (43·04±5·93 fmol/mg protein, n=13).DNA synthesis by mammary alveolar epithelial cells cultured on collagen gels was increased twofold by TGF-a (maximum response at 10 μg/l; 1·8 nmol/l) but not by EGF. Cells derived from 15- to 20-week pregnant sheep responded significantly to TGF-α on day 3 of culture, but the response was delayed to day 4–5 of culture in cells from other physiological states. Dose–response was not significantly affected. TGF-α and IGF-I produced an additive effect on DNA synthesis. Oestradiol (10−12 to 10−9 m), a potential stimulator of the TGF-α gene, did not stimulate DNA synthesis alone, or in combination with IGF-I. It is concluded that growth factors acting via the EGF receptor play a role in ruminant mammary development, but whether they mediate oestradiol effects remains unresolved.Journal of Endocrinology (1995) 144, 165–171

Journal

Journal of Endocrinology – Bioscientifica

Published: Jan 1, 1995

There are no references for this article.