AJP - Endocrinology and Metabolism, Vol 263, Issue 4 E766-E771, Copyright © 1992 by American Physiological Society
Metabolism of pregnant-lactating rats is adapted to pregnancy rather than to lactation
S. Wijkstra, H. Moes and T. R. Koiter
Department of Obstetrics and Gynecology, University of Groningen, The Netherlands.
In pregnant-lactating rats implantation was induced on day 4 of lactation
so that, as an exception, lactation coincided with the period of high fetal
growth. The already present suckling litters of these animals lagged behind
in growth, but the "second" litters were at birth normal in size and
weight. Such pregnant-lactating rats were tested in vivo with intravenous
glucose loads and compared with cyclic and lactating rats. Glucose
tolerance was unaffected by the reproductive state. Pregnant-lactating rats
showed, just as during their first pregnancy, low basal glucose levels.
Their basal insulin levels and insulin responses, however, were decreased
in comparison with the first pregnancy and resembled those of lactating
rats. This may be due to an increased insulin turnover, because in vitro
insulin responsiveness and insulin content of both "pregnant-lactating" and
"pregnant" islets were increased in comparison with "cyclic" and
"lactating" islets. It was concluded that the metabolism of
pregnant-lactating rats is adapted to the pregnant rather than to the
lactational state.
