AJP - Endocrinology and Metabolism, Vol 255, Issue 3 E293-E298, Copyright © 1988 by American Physiological Society
Binding proteins for growth hormone and prolactin in rabbit kidney cytosol
A. C. Herington, J. L. Stevenson and S. I. Ymer
Medical Research Centre, Prince Henry's Hospital, Melbourne, Australia.
Two soluble, receptor-like binding proteins with apparent somatotrophic
[growth hormone (GH)] and lactogenic [prolactin (PRL)] specificities,
respectively, and that are present in rabbit kidney cytosol have now been
examined in more detail using specific GH receptor and PRL receptor
monoclonal antibodies (MAb). Gel chromatography of 125I-labeled human GH
(125I-hGH) kidney cytosol complexes in the absence of these MAbs revealed
two specifically bound regions of radioactivity at molecular weights (MW)
of approximately 120,000 and approximately 60,000, which are similar in
size to complexes formed by the native GH receptor of rabbit liver cytosol
and the PRL receptor of mammary gland. Co-incubation with GH-receptor MAb
inhibited 125I-hGH binding only to the higher MW (120,000) species, whereas
the PRL-receptor MAb inhibited only the lower MW (60,000) species, thus
establishing definitively the hormonal specificities of the two binding
proteins. The presence of both GH- and PRL-specific binding subunits in
cytosol was confirmed using covalent cross-linking techniques. No GH
binding protein was detected in kidney membranes. The presence of naturally
soluble, receptor-like binding proteins for GH and PRL in kidney cytosol
preparations raises the possibility of their playing a role in the
intracellular regulation of kidney function and/or metabolism.
