Need of dietary energy at critical implantation time when local ovarian hormones are obligatory for conceptus development.

ABSTRACT

Role of dietary energy and local ovarian hormones in conceptus development in the rat was evaluated by giving ip injections of estrogen and progesterone under diet restricted and/or dextrose supplemented conditions, using the experimental model of ovarian compensatory hypertrophy. Replacement of estrogen on day 2 and progesterone on day 3 was necessary for conceptus development in the ipsilateral uterine horn after unilateral ovariectomy on day 2. Continuation of progesterone injection up to day 9 improved the percentage of conceptus development. Conceptus development was normal when unilateral ovariectomy was performed after day 2 of pregnancy. Compensatory increases in corpus luteum (CL) volume and the activity of delta 5 3 beta-hydroxy steroid dehydrogenase (3 beta-HSD) in contralateral ovary were observed after unilateral ovariectomy on day 2-4 of pregnancy. However, 70% diet restriction reducing the energy intake (from 90 to 27 kcal/rat/day) abolished the single dose hormone therapy effects in ipsilateral horn conceptus development and also reduced the effects of continued progesterone, percentage of contralateral horn conceptus development, compensatory changes in the CL volume and delta 5 3 beta-HSD activity of the contralateral ovary. However, dietary dextrose supplementation (increasing calorie intake from 27 to 56 kcal/rat/day) significantly improved/restored hormone response for conceptus development, compensatory changes of the CL volume and enzyme activity in contralateral ovary. The results suggest that day 2-3 of pregnancy is the critical time when local ovarian supply of estrogen and progesterone are obligatory for establishment and conceptus development in the rat. During this period adequate mobilizable source of energy is necessary for execution of hormonal message.