Abstract
Fasting plasma levels of progesterone, glucose and insulin (IRI) were systematically
investigated during a 20 days postpartum (p.p.) period in the same lactating (L) and
non lactating (NL) rats. Progesterone levels, low at the end of gestation, remain
low thereafter in NL groups; in L groups they increase on and after day 4 pp, reach
values similar to the gestational ones, and decrease only after weaning. Glucose levels,
low at the end of gestation, increase rapidly in NL group during the first 2 days
pp and reach a stable value; in L group the increase is slower but the final stable
value reached is the same. IRI levels, low at the end of gestation, increase similarly
in both groups during the first 2 days pp then they return to low values in NL group
whereas they remain elevated in L group until weaning (after which they decrease).
It is suggested that the elevated IRI levels observed in L group despite normal glucose
levels, are largely a consequence of the enhanced progesteronemia.
Key words
Lactation - Pregnancy - Progesterone - Insulin
1 These studies were presented in part at the XXV International Congress of Physiological
Sciences, July 15-31, 1971 in München (Germany) and at the 8th Annual Meeting of the
European Association for the Study of Diabetes, September 6-8, 1972 in Madrid (Spain).
2 Present adress: Laboratoire, Institut Médico-Chirurgical d'Anderlecht, B 1070 Bruxelles,
Belgium.
