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Department of Nutritional Sciences, University of California, Berkeley, CA 94720 and * Department of Animal/Range Sciences, North Dakota State University, Fargo, ND 58105
2To whom correspondence should be addressed.
A nutritionally-regulated compensatory growth regimen imposed during a
growing period from prepuberty to gestation can significantly affect
mammary development and subsequent lactation performance. The
objectives of this study were as follows: 1) to
determine whether a compensatory nutrition regimen enhances lactation
potential for the first and second lactation cycles and
2) to determine the extent to which a compensatory
nutrition regimen modulates cell proliferation, differentiation, and
apoptosis and expression of genes in mammary tissues of female rats.
Female Sprague-Dawley rats (n = 122, 35 d
of age) were randomly assigned either to the control group, with free
access to diet, or to a stair-step compensatory nutrition feeding
regimen, with an alternating 22-33-wk schedule. The regimen began
with an energy-restricted diet (40% restriction) for 2 wk,
followed by the control diet for 2 wk; this step was then repeated at
3-wk intervals. Pups of dams from the compensatory nutrition regimen
group gained more during mid-lactation than did control group pups.
Mammary tissues were obtained from early (d 2) and late (d 19)
lactating rats. Mammary tissue from the compensatory nutrition group
exhibited increased cell proliferation and greater
-glutamyltranspeptidase and ornithine decarboxylase gene expressions
than did tissue from the control group during early lactation of both
cycles. Mammary tissue from the compensatory nutrition group also had
fewer apoptotic cells than tissue from the control group during late
lactation of the first lactation cycle. These results suggest that the
compensatory nutrition regimen imposed during the peripubertal
developmental phase stimulated mammary growth and enhanced lactation
performance by affecting the expression of genes that regulate the cell
cycle.
KEY WORDS: compensatory growth lactation cell proliferation apoptosis rats
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