1. Investigación

Pregnant rats at 12 and 21 days of gestation and their virgin controls were injected intravenously with U-14C-glycerol and decapitated 1, 3, or 10 min later. The conversion of labelled glycerol to 14 C-glucose was augmented in the 21-day pregnant rats. The disappearance of the newly formed 14C-glucose from blood was faster in both 12- and 21-day pregnant rats than in their controls, being partially retained as liver 14C-glycogen. The greatest amount of radioactivity in all tissues appeared in the carcass hydrosoluble fraction. This amount was smaller in the pregnant rats. The reduced utilization of glycerol by extrahepatic tissues allowed the 21-day pregnant rats to dispose a greater amount of this substrate for gluconeogenesis.

Pieces of lumbar adipose tissue from 19-day pregnant rats and their virgin controls were incubated in the presence of albumin, glucose, U- 14C-glycerol, and either bovine insulin (200 µU/ml) or adrenaline (2.6 µM). The rate of glycerol release in the medium was augmented in both fed and 48-hour fasted pregnant rats. Insulin reduced this parameter in tissues from pregnant rats but not from controls. Adrenaline enhanced it in all groups, especially in tissues from fed pregnant rats. The rates of CO2 , fatty acids and glyceride glycerol formation from glycerol were higher and the effect of insulin was greater in pregnant than in control rats when fed. Fasting produced a decrease in all these parameters, the effect being greater in pregnant than in control rats. The augmented sensitivity of adipose tissue from the mother allows for a rapid switch from the anabolic to the catabolic state according to the necessities of the fetus.

Lumbar fat pad oieces taken from fed and 48 h starved 19-day pregnant rats and virgin controls were incubated for different times with [u-14cJ glycerol, albumin and glucose. The glycerol conversion rates to either co2 , saponified lipids and glyceride glycerol were higher in the pregnant rat tissue than in the controls. Starvation produces a greater decline in these parameters in pregnant rat tissue than in controls. The lipolysis rate was elevated in pregnant rat tissue. The augmented glycerol utilization by adipose tissue in the mother would contribute to the net deposition of fat, despite augmented lipolysis. In the starved state the enhanced lipolvsis of the mother is potenciated by a decreased reutilization of glycerol, allowing a maximal net mobilization of the fat stores.