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-MSH and
-MSH both influence postnatal rat growth and associated rat hypothalamic protein expression
1Department of Physiology, 5Department of Molecular Medicine and Pathology, 4School of Biological Sciences, University of Auckland; 2HortResearch, Mt. Albert, Auckland; and 3HortResearch, Ruakura, Hamilton, New Zealand
Submitted 3 October 2005 ; accepted in final form 15 July 2006
Desacetyl
-MSH predominates over
-MSH during development, but whether it is biologically active and has a physiological role is unclear. We compared the effects of 0.3 µg·g1·day1 desacetyl
-MSH with that of 0.3 µg·g1·day1
-MSH on postnatal body growth by administering the peptides subcutaneously daily for postnatal days 014 and also used a two-dimensional gel electrophoresis gel-based proteomic approach to analyze protein changes in hypothalami, the relay center for body weight and growth regulation, after 14 days of treatment. We found that the growth rate between days 1 and 10 was significantly decreased by desacetyl
-MSH but not by
-MSH, but by day 14, a time reported for development of a mature pattern of hypothalamic innervation, both peptides had significantly increased neonatal growth compared with PBS-treated control rats. Desacetyl
-MSH significantly increased spleen weight, but
-MSH had no effect.
-MSH significantly decreased kidney weight, but desacetyl
-MSH had no effect. Both desacetyl
-MSH and
-MSH significantly decreased brain weight. By 14 days, both peptides significantly changed expression of a number of hypothalamic proteins, specifically metabolic enzymes, cytoskeleton, signaling, and stress response proteins. We show that peripherally administered desacetyl
-MSH is biologically active and induces responses that can differ from those for
-MSH. In conclusion, desacetyl
-MSH appears to be an important regulator of neonatal rat growth.
melanocortin peptides;
-melanocyte-stimulating hormone; melanocortin receptors; proopiomelanocortin; hypothalamus
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