Changes in plasma beta-cell tropin concentrations during pregnancy in rats

The mechanisms which initiate and maintain the energy partitioning into maternal tissues during pregnancy are unknown. The present study shows that in each of the weeks prior to pregnancy in the rat, plasma beta-cell tropin (beta CT) concentrations (nmol/l) were 0.68 +/- 0.10, 0.61 +/- 0.14 and 0.73 +/- 0.11 (n = 11, mean +/- S.E.M.). During early (1-3 days) pregnancy the concentration rose to 1.32 +/- 0.26 and by early-mid (7-10 days) pregnancy they had increased to 1.96 +/- 0.41. By mid-late (14-17 days) pregnancy plasma beta CT concentration had declined to the prepregnancy concentrations (0.67 +/- 0.16). This mid-term increase in the circulating concentration of the lipogenic hormone beta CT may contribute to the deposition of lipid associated with the early period of gestation. The increased circulating beta CT could be derived from the pituitary gland neurointermediate lobe or by secretion from the placenta. It should be emphasised that the measurements in the present study represent a 'snap-shot' at discrete intervals and do not provide information about the dynamic hormonal interplay which occurs physiologically.